JPH0961678A - Semiconductor light receiving element - Google Patents

Abstract

(57) [Summary] [Purpose] In an optical subscriber system module (ONU module) that performs bidirectional optical communication using 1.3 μm light and 1.55 μm light, 1.3 μm light and 1 Although 0.55 μm light is separated, the attenuation ratio of unnecessary light components is insufficient in the current wavelength demultiplexer. Therefore, a multi-layer film filter for blocking unnecessary light is provided in the path after separation. Due to the multilayer filter, the component cost and the assembly cost increase. The purpose is to omit the multilayer filter. [Structure] A grating is provided in a part of an optical fiber to reflect unnecessary light and reduce the attenuation ratio. Omit the multilayer filter. Since the grating is formed in the optical fiber, the volume of the component does not increase at all. The number of parts does not increase either. The assembly cost does not rise. The module can be made smaller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical subscriber system ONU for bidirectional communication by passing lights of two kinds of wavelengths through the same fiber. First, bidirectional communication, ON
The U and ONU optical modules will be described.

Optical communication is the transmission of information by passing signal light through an optical fiber. In recent years, the transmission loss of an optical fiber has been remarkably reduced, and the characteristics of a semiconductor laser (hereinafter sometimes abbreviated as LD) and a semiconductor light receiving element (also sometimes abbreviated as PD) have been improved, so that optical communication has become popular. It's starting. Especially, the loss of the optical fiber is small 1.3
Attempts to transmit signals (telephones, facsimiles, television images, etc.) using light with wavelengths of μm and 1.55 μm have been actively made.

Even in the case of optical communication, the original signal is an electric signal, and therefore, there are two types of signal transmission forms as in the present electric signal. That is, low-speed digital communication and high-speed analog communication. Low-speed digital communication is used for telephone and facsimile signal transmission. Handles low bit rate digital signals. Moreover, this must be two-way communication.

High-speed analog transmission is transmission of a TV signal by wire (CATV). This is one-way communication from the broadcasting station. When adopting optical communication in which signals are transmitted by optical signals, it is possible that optical fibers for low-speed digital signals and optical fibers for high-speed analog signals may be separated. However, laying two optical fibers is expensive. We would like to be able to simultaneously perform low-speed digital two-way communication and high-speed analog one-way communication with a single optical fiber.

[0005]

2. Description of the Related Art Optical communication systems for achieving such an object are being developed. Nothing has been completed yet. However, small but experimental attempts have been made. FIG. 1 shows an outline of such an optical communication system.

There is one base station 1 and many subscriber side terminals 2. These are connected by an optical fiber 3. There is a branching device 4 on the way, and a main optical fiber is branched into an optical fiber connected to each terminal 2. The base station 1 amplifies a telephone or TV signal and outputs it as an optical signal through one optical fiber. It goes through several branches and is divided into, for example, 16 near the target home. The optical signal is split as it is. From here, 16 household optical fibers send signals to 16 households. For the base station, the home terminal is called a subscriber terminal (ONU). This is the OPTICAL NETWORK UNIT
Stands for.

In the case of a TV signal, it is one-way transmission from the base station 1. However, in the case of telephone or facsimile, signals are bidirectionally transmitted from the terminal to the base station or from the base station to the terminal. The reason for arranging the optical fibers in this way is to reduce the number of fibers in the base station and reduce the cost of laying the optical fibers. An optical subscriber system is a system in which signals are transmitted from the base station to each home by light.

The optical signal transmitted from the base station 1 is converted into an electric signal by the subscriber side terminal (ONU). The mechanism of one terminal will be described with reference to FIG. The 1.3 μm light + 1.55 μm light that has passed through the optical path a is separated by the wavelength demultiplexer 5 into 1.3 μm light and 1.55 μm light. 1.3 μm light is on the optical path b, 1.55 μm light is on the optical path c
Distributed to

The 1.55 μm light is incident on the analog PD 6 which accurately reproduces the analog light. Here, the optical signal is converted into an electrical signal. Further, after various signal processing is performed in the signal processing unit 7, the image is guided to the TV set 8 and becomes an image.

The 1.3 μm light enters a 1: 2 splitter (hereinafter referred to as an optical coupler 9) and is separated into two light rays there. One of them is received by the digital PD 10 and becomes an electric signal. This is processed by the signal processing unit 11 and guided to the telephone / facsimile machine 13. Since the telephone and the facsimile are two-way communication, it is necessary to send a signal from the terminal 2 to the base station 1. For this purpose, an electric signal given from a telephone or a facsimile is converted into a 1.3 μm optical signal by the digital LD 12. The optical signal passes through the wavelength demultiplexer 5 in the opposite direction, merges with the main optical fiber from the branching unit 4, and is transmitted to the base station 1. The optical coupler 9 is inserted in the middle of the optical fiber system in order to enable bidirectional communication by optical signals.

In this way, the subscriber system terminal 2 has 1.3
Wavelength demultiplexer 5 for separating and integrating μm light and 1.55 μm light, optical coupler 9 for two-way communication, photodiodes PD6, 10 for converting an optical signal into an electric signal, and an optical signal for an electric signal A laser diode LD12 for converting into a laser diode is required. A unit that combines a wavelength demultiplexer, an optical coupler, a PD, and an LD is called an ONU module. The present invention relates to a novel configuration of ONU module.

No ONU module has been put to practical use yet. However, many proposals have been made regarding the ONU module. An overview of these proposals, though not implemented yet.

[Conventional Example: Example of Mirror Type ONU Module] (FIG. 2) This is a structure in which a wavelength demultiplexer and an optical coupler are constituted by mirrors. The optical fiber 20 connected to the base station is guided into the module by the optical connector 21. After that, the light travels along the optical path a in the free space. Since the light emitted from the optical fiber diverges, it is collimated by the collimator lens 22. This is incident on the mirror type wavelength demultiplexer 23, and is separated into 1.3 μm light and 1.55 μm light.

The 1.3 μm light that carries the low-speed digital signal is
It passes through the optical path b in the free space and reaches the mirror type coupler 24. This is a half-mirror, and the 1.3 μm light is 1:
Reflected and transmitted at a ratio of 1. The transmitted light is a multilayer filter 2
It is led to 5. This is for more completely removing the mixed 1.55 μm light. After that, the light is focused by the lens 26, enters the digital PD 27, and is photoelectrically converted. After this, it is sent to a telephone or a facsimile machine and converted into voice and characters.

On the other hand, low-speed digital signals from telephones and facsimiles are converted from electrical signals into optical signals of 1.3 μm by the digital LD 28. The optical signal is focused by the condenser lens 29 and reflected by the coupler 24. This passes through the mirror type wavelength demultiplexer 23, and enters the optical fiber 20 through the collimator lens 22. After that, it is guided to the base station 1 by the optical fiber 20.

1.55μ for carrying high speed digital signals
The m light is reflected by the mirror type wavelength demultiplexer 23,
Separated from 1.3 μm light. The 1.55 μm light passes through the optical path c, the multilayer film filter 30, is focused by the lens 31, passes through the optical connector 32, and is transmitted to the analog PD by the optical fiber 33. After being converted from an optical signal to an electrical signal and subjected to various kinds of signal processing, it is guided to a TV set.

The trial of the ONU module in which the wavelength demultiplexer and the optical coupler are manufactured by the mirrors as described above is described in Mitsuru Yumoto, Tatsuro Kunikane, Tatsuhiro Okawara, Takashi Yokota, "Low-Cost Single-Mode WDM Module," The Institute of Electronics, Information and Communication Engineers, 1990. Spring National Convention Proposal No. C-203 (P4-2
58) Akihiro Adachi, Kuniaki Motojima, Yasuo Nakajima, Junichiro Yamashita, Kumio Kasahara "Small and thin optical multiplexer / demultiplexer module" Proceeding No. C-222 of IEICE Autumn National Conference 1990
4-264) and the like.

The disadvantage of this system is that the light is 1.3 μm,
This means that the separation of the 1.55 μm light is incomplete. Incomplete separation causes crosstalk. Noise will enter both the telephone and TV. The reason is as follows. With the mirror type wavelength demultiplexer 23 alone, the light is 1.3 μm,
It is difficult to completely separate 1.55 μm light. The mirror type wavelength demultiplexer is made by stacking multiple layers of dielectric thin films having different refractions so that light of a certain wavelength is reflected and light of a certain wavelength is transmitted. It transmits 1.3 μm light and
It is designed to totally reflect 55 μm light in the direction of 45 degrees. However, the attenuation ratio of the light on the other side is at most 1/100
Is nothing more than a degree.

In order to put this module into practical use, 1.3
The 1.55 μm optical power leaking to the μm receiving side is 1/1
It must be 0000 or less. Similarly, 1.55 μm
The 1.3 μm optical power leaking to the receiving side needs to be 1/10000 or less. Of the light that was not chosen like this,
The ratio of the selected light to the power will be referred to as the attenuation ratio here.

In other words, the module is on the 1.3 μm side,
An attenuation ratio of 10 ⁻⁴ or less is required on the 1.55 μm side. On the other hand, the attenuation ratio of the mirror type wavelength demultiplexer is 10 ^-2 . 10 ^-2
The damping ratio of is not enough. Therefore, the multilayer filters 30 and 25 that pass only the light of the desired wavelength are provided in the respective optical paths. A spider 1 with a wavelength demultiplexer and a multilayer filter
The damping ratio of 0 ^-4 is satisfied.

[Conventional Example: Example of Mirror Type ONU Module] (FIG. 3) FIG. 3 shows an ONU module using a planar waveguide, which has been actively studied recently. For example, Hiroshi Terui, Satoshi Sekine, Morio Kobayashi, Mitsuru Naganuma “Low-speed optical subscriber branch optical module”, NTTR & D Vol. 42, N
o. 7, p903-912, (1993) and the like. The advantage of the waveguide type module is that the number of parts can be reduced and the size can be reduced.

In FIG. 3A, the end portion of the input single mode fiber 34 is joined to the end surface of the PLC (planar waveguide) 35. An optical waveguide 36 is vertically formed on the PLC 35. This branches into two optical waveguides 38 and 39 at a branch point 37 on the way. The optical waveguide 38 is 1.3
This is the optical path on the receiving side for μm light. Optical waveguide 39 is 1.3 μm
It becomes the optical path on the transmission side of light. The branch point 37 constitutes an optical coupler 40 that multiplexes and demultiplexes transmitted and received light.

Further, an optical waveguide 41 is provided on the PLC 35. It is close to the optical waveguide 36 at the starting end 42. At the beginning 42, the optical waveguides 36, 41 can exchange optical power with each other. The wavelength demultiplexer 43 is formed by giving wavelength selectivity to the exchange of optical power.
By appropriately selecting the distance and length of the proximity portion, all 1.3 μm light from the optical path a to the optical path b, and 1.55 μm light to the optical path c.
Are allocated to each.

The 1.3 μm light is received by the digital PD 45 from the waveguide 38 through the multilayer filter 44. The multilayer filter 44 is a filter for removing the 1.55 μm component. On the other hand, the digital electric signal from the telephone and the facsimile is 1.3 by the digital LD 46.
It is converted into an optical signal of μm. The optical signal enters the end portion 48 of the optical waveguide 39 through the condenser lens 47. The transmitted optical signal merges into the optical path b at the branch point 37 and propagates from the waveguide 36 to the optical fiber 34. This is finally sent to the base station.

1.5 separated by the wavelength demultiplexer 43
The 5 μm light passes through the optical waveguide 41 and passes through the multilayer filter 49.
After completely removing the 1.3 μm light, the light is incident on the analog output single mode fiber 50.

PLC (Planar Lightwave)
Circuit) 35 is shown in FIG. Si
A quartz-based cladding layer 53 is deposited on the substrate 52. Further, impurities for increasing the refractive index are continuously doped to form a region (core) having a high refractive index in a linear shape. This is the optical waveguide 3
8, 39, 41. For example, Ge is used as the impurity. Quartz uses 1.3 μm light, 1.55
This is because it is transparent to μm light. The wavelength demultiplexer 43 is made by partially approaching such an optical waveguide. Moreover, it can be used as an optical coupler by forming a Y branch. For such a silica-based optical waveguide,

Masao Kawauchi, "Present and Future of Planar Lightwave Circuit Technology," NTT R & D Vol. 43, No. 1
1, p1273-1280 (1994). Wavelength demultiplexer with optical waveguide 4
The damping ratio of 3 is about 1/100 at most. Damping ratio is 1
Multilayer filters 44, 49 are glued to the ends of the respective optical waveguides 38, 41 in order to achieve 0 ^-4 .

Since the light from the LD 46 spreads, a condenser lens 47
The light is converged by and is made incident on the core of the end face of the optical waveguide 39. However, no lenses are provided for the remaining two beams. Since the waveguide 38 and the digital PD 45 are extremely close to each other, no lens is required. Since the analog output fiber 50 is joined to the end face of the waveguide 41, no lens is required between them. It is said that the module using the silica-based optical waveguide is excellent in familiarity with the optical fiber because the PLC is made of the same material as the optical fiber and the size of the waveguide is almost the same. Modules that use curved optical waveguides

Masaki Kuribayashi, Hideki Isono, Tatsuro Kunikane, Yasuhiro Omori, Toshiyuki Emori "Optical Bidirectional Optical Module with WDM Using Silica-based Optical Waveguide" 1993 IEICE Autumn National Conference Proposal No. C-158 (P4) 238).

[Conventional example: example of optical fiber wavelength demultiplexer]
(Fig. 4) A wavelength demultiplexer using an optical fiber and an optical coupler using an optical fiber have already been industrialized. An ONU module, which is entirely composed of optical fibers, has also been proposed. Since the wavelength separation is not perfect only with the optical fiber wavelength demultiplexer, a multilayer filter is inserted in a small space where the optical fibers are butted to exclude light of an unnecessary wavelength. The outline will be described with reference to FIG.

The optical signal propagating through the single mode fiber 60 is guided to the ONU module by the optical connector 61. From the path a to the optical fiber wavelength demultiplexer 62,
Here, it is separated into 1.3 μm light and 1.55 μm light.
The 1.3 μm light further passes through the optical connector 63 and reaches the optical fiber coupler 64. This is for coupling the transmitted light and the received light. The route b branches into optical fibers 66 and 67 at a branch point 65. Both the wavelength demultiplexer and the optical fiber coupler are designed to selectively distribute the optical power by bringing the cores of two optical fibers close to each other.

A coupler or a wavelength demultiplexer can be used depending on the approach distance and length. The optical fiber 66 passes through the multilayer film filter 68, reaches the optical connector 69, and reaches the digital PD.
Received by module 70. The transmitted light is electro-optically converted by the digital LD module 81. Enter the ONU module through the optical connector 80, and then the coupler 6
It is guided to the path b by 4 and sent out from the optical connector 61 to the optical fiber 60.

As described above, the wavelength demultiplexer, the coupler, and the part connecting them are all made of the optical fiber. The optical fiber can be bent freely, can be joined to the components by fusion, and the distance can be adjusted freely. No matter how the electrical circuits are arranged, they can be connected by optical fibers. There is an advantage that the degree of freedom of the circuit configuration is high.

[Conventional Example of Semiconductor Light-Receiving Element] An example of the proposal of the ONU module used for bidirectional optical communication has been described above. In any case, a light receiving element for detecting 1.3 μm light and 1.55 μm light is required. FIG. 5 is a vertical perspective view showing an example of a conventional semiconductor light receiving element.

The package 86 of the light receiving element is made of metal such as iron, kovar, copper tungsten. Package 8
6 is provided with a plurality of lead pins 87, 88, 89 below. The photodiode chip 91 is soldered to the upper surface of the package 86 via the submount 90 (AuG
e, AuSn). The submount 90 is formed by metallizing both sides of ceramic. Submount may be omitted.

The electrodes of the photodiode 91 and the surface of the submount 90 are connected to the lead pins 87 and 89 by wires. A cap 93 having a spherical lens 92 is fixed to the upper surface of the package 86. The center of the ball lens 92,
The center of the photodiode chip 91 is made to coincide with the direction perpendicular to the plane. Further, a cylindrical sleeve 94 is fixed to the package 86.

A ferrule holder-95 is welded onto the sleeve 94. There is a hole 96 in the center of the ferrule holder 95, and the ferrule 97 is inserted therein. The ferrule 97 holds the tip 99 of the single mode fiber 98. The end face is cut so as to form an inclination of 8 degrees. It is aligned so that the light emitted from the optical fiber forms an image on the photodiode chip. Furthermore, in order to prevent the strong bending of the optical fiber 98, the bend limiter 104 made of an elastic material is attached to the ferrule holder-9.
Fit in 5.

This is the digital PD that appears in FIGS.
It corresponds to any of the analog PDs. The signal light propagates through the optical fiber and is emitted from the tip of the optical fiber. This is condensed by the lens and enters the photodiode. Here, it is photoelectrically converted into an electric signal. As the photodiode, a PIN-PD having an InGaAs light receiving layer, which has a wide sensitivity to light having a wavelength of 1.0 μm to 1.65 μm, is used. A quartz optical fiber is used as the optical fiber.

[0039]

SUMMARY OF THE INVENTION 1.3 μm light, 1.5
The photodiodes for sensing 5 μm light are all I
It uses nGaAs as a light-receiving layer and has sufficient sensitivity to near-infrared light. 1.3μm light and 1.55μ by wavelength demultiplexer
m The light is separated, but the two cannot be separated sufficiently.

As described at the beginning, if 1.55 μm light is mixed into the photodiode for 1.3 μm light even at 1/1000, the TV image is disturbed, or the telephone or the facsimile is noisy. In order to avoid noise due to interference, the attenuation ratio should be 1/10000 or less.
The multilayer filters 25, 30, 44, 49, 68, 83 are inserted in order to compensate for the shortage of the attenuation ratio of the existing wavelength demultiplexer.

In the conventional ONU module, in order to completely separate the 1.3 μm light and the 1.55 μm light, it was necessary to insert the multilayer filter somewhere in the path after the separation. This is because InGaAs, which is a light receiving element, has high sensitivity to light of any wavelength. A multilayer filter is a stack of dielectric thin films of appropriate refraction and thickness. The wavelength selectivity can be given by selecting the refraction and thickness.

Several structures have been proposed in which a filter having wavelength selectivity is inserted immediately before the light receiving element. Both are bulky because they are made of dielectric multilayer film, and the cost of parts is high.
There is a drawback that it impairs the freedom of component placement.

JP-A-62-229209 "Light receiving device" ... A wavelength selection filter is attached to the end face of the fiber. JP-A-62-229207 "Light receiving device" ... A wavelength selection filter is attached on a window glass of a light receiving element. Japanese Unexamined Patent Publication No. 63-29714 "Photoreceptor Module with Dielectric Multilayer Film" ... A filter made of a dielectric multilayer film is sandwiched between an optical fiber and a light receiving element. These are designed as a light receiving element of a wavelength division multiplexing transmission / reception system.

Since the ONU module uses light of two different wavelengths, two multilayer filters are required.
The insertion of the multilayer filter increases the number of parts and increases the cost of parts. Not only that, but the number of assembly steps is increased. It also requires space to insert the filter.

It is a first object of the present invention to provide a semiconductor light receiving element module which overcomes the problems of the multilayer film filter and can reduce the attenuation ratio of unnecessary wavelength components without increasing the number of parts. It is the purpose of 1. O can be downsized by omitting the multilayer filter.
It is a second object of the invention to enable NU modules. O that makes it easier to assemble while keeping the damping ratio small
It is a third object of the present invention to provide a NU module.

[0046]

According to the present invention, an unnecessary wavelength component is removed by forming an optical fiber grating having wavelength selectivity in a part of an optical fiber inside a light receiving element module. As shown in FIG. 5, the light receiving element module holds one end of an optical fiber for guiding signal light by a ferrule. An optical fiber grating is provided on a part of this optical fiber.

The grating (grid) is originally formed by providing a large number of parallel grooves at regular intervals on a plane. When white light is applied, the diffraction direction is different for each wavelength, so it is possible to separate light with different wavelengths. That is, it is used for a spectroscope. The original grating has a large number of parallel grooves on a two-dimensional surface and has a spectral effect. However, an optical fiber grating is used here. This is because when a Ge-doped quartz optical fiber is subjected to hydrogenation treatment and laser light having a wavelength near 244 nm is irradiated onto the optical fiber under the condition that interference fringes are formed, a periodic change in the refractive index occurs in the optical fiber. It was the one. The change in refractive index is on the order of 10 ^-5 .

Although the change in the refractive index is slight, if the length is to some extent, light having a wavelength twice the period P (λ = 2n)
P) can be completely reflected. Unlike the spatial grating, the reflected wavelength does not change depending on the direction. Since the optical fiber itself is one-dimensional, the grating of the optical fiber reflects light of a specific wavelength. Of course, the reflection wavelength has a certain width.

Optical fiber gratings have been proposed by several papers. However, it is not widely known even now, so I will explain it here. For example, KO Hill, Y. Fujii, DC Johnson and BSKaw
asaki, Appl. Phys. Lett., 32 (1978) p647 It is a report that the phenomenon of optical fiber grating was discovered. It is said that a Ge-doped quartz optical fiber was irradiated with light of an argon laser by a two-beam interference method to generate a periodic change in refractive index.

(10) James P. Bernardin & NM Lawand
y, "Dynamics of the formation of Bragg gratings in
germanosilicate optical fibers ", Optics Communica
tionsVol.79, No.3,4, p194 (1990) The Kramers-Kronig mechanism, dipole action, and compression model proposed so far cannot fully explain the large change in refractive index of 10 ^-5 . .

Therefore, a model of the time variation of the density of oxygen defects in Si-Ge due to two-photon absorption is made, and the phenomenon in which the oxygen defect density is increased by irradiation with laser light is explained.
It is said that the refractive index increases as the number of oxygen defects increases.
This explains that the irradiation of laser light causes two-photon absorption, which causes the refractive index to increase with time. The use is not mentioned.

(11) G. Meltz, WW Morey & WH Gle
nn, "Formation of Bragg gratings in optical fibers b
ya transverse holographic method ", Optics Letter
s, Vol.14, No.15 p823, (1989) This describes forming a grating in a Ge fiber by a holographic method. Wavelength 48
The light source is an excimer laser of 6 nm to 500 nm. This is made into a second harmonic by a non-linear crystal to obtain 244 nm light. This is irradiated onto the Ge-doped optical fiber by two-beam interference exposure. As a result, an optical fiber having strong absorption at 576.1 nm was obtained.

(12) Published Patent Publication No. 62-50005
2 "Method of forming grating in optical fiber" This is a method of forming a plurality of gratings in one optical fiber by a two-beam interference exposure method. We have proposed a sensor that attaches this fiber to an object and senses strain.

(13) Maki Inai, Masumi Ito, Toru Inoue "Fabrication of high reflectivity fiber grating using hydrogen-treated fiber" IEICE 94 Autumn Meeting Lecture No. C-2
08 (1994) states that it has been discovered that hydrogen treatment in Ge-doped quartz fiber increases the change in refractive index from 10 ⁻⁵ to 10 ⁻³ .

(14) Toru Inoue, Masakazu Mobara, Masumi Ito, Maki Inai, Yoji Hattori "On Making and Application of Fiber Gratings" IEICE Technical Report OPE94-
5, PP25-30 (1994) This introduces a method of making an optical fiber grating, a method of increasing the refractive index difference of the grating, and applications.

The most promising application is application to a fiber laser. This is a laser utilizing the excellent amplification factor of Er-doped fiber. One of the resonators is a gold mirror surface and the other is an optical fiber grating. When excitation light (1.48 μm) is incident from the coupler and the Er fiber is excited, oscillation light having a center wavelength of 1.55 μm is obtained. The light repeatedly reflected by the resonator is amplified and laser light of this wavelength is obtained. When tension is applied to the grating to pull it, the period of the grating is extended, so the reflected wavelength is different.

Therefore, it should be a wavelength tunable laser.
FIG. 17 is a grating reflection spectrum of the hydrogen-doped fiber. It shows a high reflectance for light of 1549 nm to 1551 nm. When the optical fiber is pulled, this reflectance distribution shifts. It is said that when the tension is changed from 0 g to 2500 g, the oscillation wavelength linearly changes from 1551 nm to 1583 nm.

Another proposed application of the grating fiber is a temperature sensor. When the temperature rises, the optical fiber extends and the grating spacing of the grating also extends. Then, the wavelength of the reflected light is different. Then you know the temperature.

(15) Japanese Unexamined Patent Publication (Kokai) No. 4-288510 "Structure of an optical waveguide having a Bragg diffraction grating processing for changing the direction of light inside". This is formed by obliquely forming a grating in an optical fiber at equal intervals. It takes out light to the outside. It is not used as a reflector. It's an unusual usage. When the grating interval is P and the wavelength of light is λ, P = λ cos
Light is emitted in a direction that satisfies θ. When the grating is slanted, the direction of emitted light is determined in the direction of the grating surface. The light is confined in the core due to the difference in the refractive index between the core and the clad of the optical fiber, but it is doubtful whether the total reflection in the clad can be blocked by the increase in the refractive index of the optical fiber grating.

As described above, the optical fiber grating is described in the documents (15) to (15). When the Ge-doped quartz glass optical fiber is irradiated with ultraviolet rays, the refractive index of that portion changes. Therefore, by irradiating ultraviolet rays so as to have a certain spatial period, it is possible to form a portion where the refractive index changes periodically. This makes it possible to fabricate the reflector inside the optical fiber.

The lattice originally has a two-dimensional spread. The optical fiber has a one-dimensional spread from the beginning. Therefore, it is a bit strange to call a grating formed on an optical fiber. But like the grid,
Since the change in the refractive index changes periodically, this is called an optical fiber grating.

There are several ways to make an optical fiber grating. In the two-beam interferometry method, laser light (around λ = 240 nm) is split into two beams, and irradiation is performed from both sides of the surface normal at the same inclination angle to form interference fringes. Cause a change in refraction. Alternatively, the laser light is divided into two and made incident on different prisms having a cross section of an isosceles right triangle, and the laser light is irradiated onto an optical fiber placed under the prism. Gratings with different periods can be created by changing the angle of incidence.

However, by irradiation with ultraviolet rays,
It is not yet clear whether the refractive index of the doped optical fiber will increase. One theory is that for Ge-doped glass, G
The absorption band of the e-Si bond exists near 240 nm. The Ge—Si bond is broken by absorbing the laser light. The electrons released by the breakage are trapped by Ge and a new absorption band is formed. The presence of this absorption band changes the refraction.

This is a change in the refractive index called the Kramers-Kronig mechanism. Another theory is Ge-S
When the bond of i is broken, an electron is emitted, and this is G
It is trapped by e, which creates a hyperbolic moment and produces a DC electric field, so that the refractive index changes due to the electro-optic effect. Another theory is that UV irradiation breaks the glass bond and destroys the glass mechanism. The density is increased and the refractive index is increased.

All are speculative and not conclusive. However, the phenomenon that the refractive index increases due to ultraviolet irradiation is recognized. The wavelength of light reflected by the optical fiber grating is λ = 2nP. Here, P is the pitch of the grating, and n is the refractive index. Although the core refractive index of the optical fiber is fixed, it is possible to reflect light of an arbitrary wavelength by changing the pitch P.

An application of the optical fiber grating is a fiber laser resonator. The Er-doped fiber amplifies the signal light by passing light. Therefore, two gratings are provided at a certain portion to repeatedly reflect light and amplify the power to make a laser.

In the present invention, such an optical fiber grating is provided in the optical fiber inside the light receiving element module. Since the place where the optical fiber originally exists is replaced by the optical fiber that forms the grating,
Does not require extra space. Furthermore, since an object having the same function as the multilayer film is provided inside the module, assembly is not difficult. Since the number of parts does not increase, the parts cost is almost the same as that of the product without the multilayer film.

[0068]

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 6 shows the structure of an optical fiber grating. The optical fiber 99 comprises a central core 100 and a clad 101 surrounding the core 100. In the case of a single mode fiber, the core diameter is 10 μm. Clad diameter is 1
25 μm. A portion 102 in which the refractive index periodically changes is formed inside the core by an ultraviolet two-beam interference method. The period of the refractive index fringes of the grating portion 102 is λ ₂ =
Determine so that it becomes nP. And light having a wavelength of lambda ₁ here, put a light having a wavelength of lambda _2, the light of lambda ₂ is reflected. Λ ₂ cannot pass through the refractive index changing portion 102. λ ₂ does not pass, but λ ₁ passes. This is 1.55 μm
The gist of the present invention is that it is used for an ONU module in which it is essential to separate light and 1.3 μm light.

FIG. 7 shows an optical fiber of the light receiving element module in which an optical fiber grating is formed. The grating portion 102 is provided in the core 100 portion of the tip 99 of the optical fiber, and this is inserted into the hole of the ferrule 97 and fixed. The end face 103 is obliquely polished. This is to prevent the returning light from entering the semiconductor laser.
In FIG. 7, the left end is further continuous to the left.

The optical fiber is a quartz single mode fiber containing 6 wt% of GeO ₂ . This was subjected to hydrogenation treatment, and the second harmonic of the argon laser (SHG: λ =
244 nm) was applied to the optical fiber by the two-beam interference exposure method. The hydrogenation treatment is performed to make it easier to change the refractive index due to laser light irradiation. The length of the grating portion is 5 mm. The ferrule is made of stainless steel and has a length of about 15 mm.

1.55 to select 1.3 μm light
The period is determined so that μm is reflected. λ ₂ = 1.5
P is determined so that 5 μm = nP. As a result, a reflectance of 99% or more was obtained for 1.55 μm light.
This means that the damping ratio can be reduced to 1/100 or less. Since some form of wavelength demultiplexer is provided separately, the total attenuation ratio is 10 ^-4 with the attenuation ratio.
It can be: If it is desired to further reduce the attenuation ratio, the length of the grating may be further increased. If the length is doubled, the damping ratio will be 2
It decreases with the power.

[0072]

【Example】

[Example: Having a grating in a module]
FIG. 8 is a vertical perspective view of a semiconductor light receiving element module according to an embodiment of the present invention. It is written so as to match FIG. The only difference is that a grating is provided on the optical fiber.

The package 86 of the light receiving element is made of metal such as iron, kovar, and copper tungsten. Diameter is 5.6
mm. The package 86 includes a plurality of lead pins 87, 88, 89 below. The photodiode chip 91 is soldered (AuGe, AuSn) to the upper surface of the package 86 via the submount 90. The submount 90 is formed by metallizing both sides of ceramic. The submount is here alumina.

The electrodes of the photodiode 91 and the surface of the submount 90 are connected to the lead pins 87 and 89 by a gold wire having a diameter of 20 μm. A cap 93 having a spherical lens 92 is fixed to the upper surface of the package 86. The cap 93 is welded in a nitrogen atmosphere to hermetically seal the inside. Here, the center of the spherical lens 92 and the photodiode chip 91
The center of is aligned with the direction perpendicular to the plane. Further, a cylindrical sleeve 94 is fixed to the package 86 by electric welding.

The single mode fiber is a quartz fiber containing 6% by weight of GeO ₂ as described above. After hydrogenation treatment, light having a wavelength of 244 nm is applied to the tip of the optical fiber by a two-beam interference exposure method to form interference fringes and cause a periodic change in the refractive index.
A grating is formed in the optical fiber. The length of the grating is 5 mm.

The tip 99 of this single mode fiber 98 is inserted into the hole 96 of the ferrule holder-95. With the ferrule holder-95 and the sleeve 94 in close proximity to each other, the light from the optical fiber is detected by the light-receiving element, and the sleeve is moved in the direction perpendicular to the axis to position the ferrule holder-95 on the sleeve so as to maximize the amount of light. Decide YA
Both are welded by G laser. Further, the ferrule is moved in the axial direction to find the optimum coupling position, and the ferrule is welded to the ferrule holder by the YAG laser. That is, the ferrule holder and the sleeve, and the ferrule holder and the ferrule are fixed so that the light emitted from the optical fiber is focused on the light receiving portion of the PD chip.

The end face is cut so as to form an inclination of 8 degrees. It is aligned so that the light emitted from the optical fiber forms an image on the photodiode chip. Further optical fiber 9
The bend limiter 104 made of an elastic material is fitted into the ferrule holder-95 in order to prevent the strong bending of No. 8.

This is a light receiving element module for receiving 1.3 μm light. The PD itself has a sensitivity of 1.55 μm. However, since the tip end 99 of the optical fiber has the fiber grating 102, the attenuation ratio of 1.55 μm light can be reduced to 1/100. Since the light of 1.55 μm is also blocked by the demultiplexer, the attenuation ratio of 10 ⁻⁴ or less can be combined with this.

Similarly, only 1.55 μm light is transmitted, and
A semiconductor light receiving element module that reflects 3 μm light was also manufactured. The light-receiving layer is InGaAs, which is the same as that described above. However, the pitch P of the grating part is different. This time, the pitch is determined under the condition of 2nP = 1.3 μm. In this case, the length of the grating is 4mm
It is. As a result, 1.3 μm light can be reduced to 1/100 or less.

Thus, the semiconductor light receiving element module was prepared, and these were incorporated into the optical fiber type ONU module shown in FIG. However, the multilayer filters 68 and 83 are removed, and the light receiving element module of the present invention is used for the digital PD module 70 and the analog PD module 85. That is, the demultiplexer and the coupler use a combination of optical fibers.

According to this, the digital PD module 7
In the output of 0 (light of 1.3 μm was received), the noise of 1.55 μm was attenuated to 1/10000 or less. 1.3 μm light is 1 for analog PD module
It was attenuated to / 10 000 or less. Since the noise can be reduced to 10 ⁻⁴ or less, it was found that it is practically very effective since it does not enter the telephone or TV. Since the multilayer filter can be omitted, the number of parts can be reduced,
The cost can be reduced and the size can be reduced.

If the idea of the present invention that an optical fiber grating is used for eliminating unnecessary light is realized, it is possible that the grating filter 109 is provided in a part of the optical fiber 111 outside the module 110 as shown in FIG. There could be The grating is formed outside the optical fiber, not inside the module. This has the advantage that the semiconductor light receiving element module according to the conventional example shown in FIG. 5 can be used as it is.

However, the inventor does not like the configuration shown in FIG. Such things would complicate the assembly work. Also, since the grating part is exposed to the outside, it takes time and effort to put it in a protective case or fix it separately. Furthermore, handling is inconvenient. There is a problem in downsizing.

[Embodiment Using Zirconia Capillary] In addition to directly inserting the end of the optical fiber into the stainless pipe, there is also one in which the end of the optical fiber 112 is inserted into the ceramic capillary 114 as shown in FIG. This is a zirconia capillary 114.
A capillary is put in the ferrule 113 and integrated to polish the end face obliquely. In this example, the other end is FC connector 1
15 for allowing coupling to other optical elements by the zirconia ferrule 116. It can also be connected to an optical power meter. Even in this case, a grating is provided at the tip of the optical fiber inside the ferrule. This is a pigtail type connector.

[Embodiment Receptacle Type] The present invention can be applied to the receptacle type module 117 as well as the pigtail type connector. FIG.
This will be described with reference to 1. The tip of the fiber cord 118 is stripped of its coating so that the glass portion is exposed. The tip portion is protected by a ferrule 119 such as zirconia.
In this case, the tip of the single mode fiber 120 is roundly polished. The ferrule 119 is fixed to the housing 121 of one connector. Housing 12
On the outer peripheral portion of 1, there is a cap nut 122 for fitting. A key 123 for projecting a circumferential position projects forward.

The other connector is provided with a photodiode having a lens. The lens holder-124 is a metal cylindrical member. A spherical lens 125 is fitted inside. A fiber holder-126 is provided at the end of the cylinder, and a dummy fiber 127 is fixed to the fiber holder-126. The dummy fiber is a short optical fiber and its end is cut obliquely. This is to prevent returning light. The characteristic is that the dummy fiber is provided with a grating. As a result, unnecessary light is reflected so that it cannot reach the PD.

A housing 128 for inserting the ferrule is welded to the end of the lens holder-124.
The flange portion 129 of the housing 128 is provided with a set screw hole 130. A male screw 131 is engraved on the front end of the housing 128. This can be screwed into the fitting cap nut 122. A cylindrical sleeve 132 is fitted in the central axis hole of the housing 128. This is a member for inserting the ferrule 119.

A package 133 is provided at the other end of the lens holder-124. The submount 134 is soldered to the upper surface of the package 133. Further, the PD chip 135 is die-bonded on this. Chip 13
The electrode of No. 5 and the submount 134 are connected to the lead pin 136 by the wire 137. Light receiving element chip 135
Is sealed by a window cap 138. A window glass 139 for sealing is provided on the window.

The housings 121 and 128 can be joined by inserting the ferrule 119 into the sleeve 132 and screwing the cap nut 122 into the screw 131. In this case, the tip of the single mode fiber 120 contacts the dummy fiber 127. Light is fiber 120
To fiber 127.

An example in which the present invention is applied to a receptacle type light receiving element module has been described. The novel part is that the optical fiber for dummy is provided with a grating to completely eliminate unnecessary light. Also in this example, the grating is not provided outside the housing. A grating is formed on the dummy fiber inside the housing. It is suitable for downsizing, has the advantages of not increasing the number of parts and being convenient to handle. Since it is supported by the holder, deterioration of the grating portion can be prevented.

[Application to Butterfly Type Package] The present invention can be applied to semiconductor light receiving elements housed in various types of packages. FIG. 12 shows an example applied to a light receiving element of a butterfly type package. The butterfly type light receiving element 140 is one in which a light receiving element chip and a condenser lens are housed inside a flat plate type package 141. An appropriate number of lead pins 1 are provided on the side surface of the package 141.
42 is provided so as to extend parallel to the plane. It is called a butterfly type because of the shape of the pin.

At the center of the package 141 is a lens holder-143, which holds the convex lens 144. A chip carrier 150 is provided at the innermost portion on the axis, and the photodiode chip 151 is fixed to the lens side surface of the chip carrier 150. An opening 145 is formed on the opposite end surface of the package 141, and a cylindrical ferrule 14 with a collar is formed there.
6 is inserted. The tip of a single mode fiber 147 is inserted into the ferrule 146. A grating portion 149 is formed at the tip of the fiber. This prevents unwanted light from entering the package. Also in this case, the part where the grating is formed is inside the package and is protected by the ferrule. Prevent that part from deteriorating.

[PD of two-wavelength optical communication simpler than the embodiment
Application to Module] The one described above uses 1.3 μm light bidirectionally and 1.55 μm light unidirectionally. More simply, it is assumed that the ONU module uses 1.3 μm light only for transmission and 1.55 μm light only for reception. In this case, if the conventional method is used,
m and 1.55 μm are separated, and further a multilayer filter for removing 1.3 μm is required before the 1.55 μm light receiving element. In such a case, the present invention can omit the multilayer filter and replace the wavelength demultiplexer itself with a coupler. There are also such advantages.

FIG. 13 shows the configuration of a conventional example using an optical fiber for two-wavelength optical communication. The single mode fiber connecting to the base station is connected to the optical fiber in the module by the optical connector 152. This is an optical fiber wavelength demultiplexer (W
DM) 153 separates the light into 1.3 μm light and 1.55 μm light. In this system, 1.3 μm light is not used for reception, so ideally there is no 1.3 μm component. However, signals from other ONU modules may be mixed, and 1.3 μm and 1.55 μm must be separated. Therefore, the wavelength demultiplexer 153 is used.

The transmission signal is converted from light to light by the LD module 158, the optical fiber 157 and the optical connector 156.
Through the optical fiber 154 to the wavelength demultiplexer 153. The 1.55 μm light separated by the wavelength demultiplexer passes through the multilayer filter 159, the optical connector 160, and enters the PD module 161. Here, the received optical signal is converted into an electric signal. Since the input fiber also includes 1.3 μm light, it also requires the multilayer filter 159,
A wavelength demultiplexer is also essential.

However, by applying the present invention to the light receiving element module, the structure can be further simplified. FIG. 14 shows a system constructed assuming that the present invention is applied.
The input single mode fiber 162 is an optical connector 163.
After entering the ONU module, the optical fiber coupler 1
It is simply divided into two by 64. The optical coupler 164 is merely a device for transmitting 1.3 μm transmitted light and 1.55 μm received light through one fiber 162.

The transmitted electric signal is converted into an optical signal by the laser module 171. This passes through the optical fiber 170 and goes out from the optical connector 168 and the optical fiber 166 to the fiber 162.

1.5 divided by the coupler 164.
The 5 μm light passes through the optical fiber 167 and the optical connector 169 and enters the PD module 173. The light receiving element module 173 is the module of the present invention. The optical fiber inside the ferrule is provided with a grating that reflects 1.3 μm light. Even if the light traveling from the fiber 162 toward the module contains a 1.3 μm component, the received light may be separated by the coupler without using the wavelength demultiplexer. The 1.3 μm light is excluded by the grating, does not enter the light-receiving element chip, and does not cause noise.

By adding a grating to the light receiving element module, both the wavelength demultiplexer and the dielectric multilayer film filter can be omitted. The optical demultiplexer replaces the wavelength demultiplexer, but the coupler is much easier and cheaper to manufacture than the wavelength demultiplexer.

[Example of application to bell-shaped light receiving element module] An example in which the present invention is applied to a bell-shaped light receiving element will be described with reference to FIG. Optical fiber 1
A ferrule 175 is attached to the tip of 74. The tip of the ferrule is cut diagonally. Ferrule 17
5 is inserted into the through hole 202 formed in the boss portion of the conical housing 176. The wide end surface of the housing 176 is fixed to the upper surface of the cylindrical sleeve 177.

The disk-shaped header 178 has several lead pins 179. The photodiode chip 181 is bonded to the mount 180. Photodiode 1
The electrode of 81 and the pin 179 are connected by the wire 182. The top surface of the header 178 is further covered by a cap 183 having a window 184. The window 184 is fitted with glass. The space of the chip is hermetically sealed with nitrogen gas.

A lens 186 is provided in the opening 185 above the sleeve 177. The photodiode chip is illuminated, the light is observed from above the condenser lens 186, and after alignment, the end surface 188 of the sleeve 177 is YAG welded at point A. Further, an optical power meter is provided at the other end of the optical fiber 174, the positions of the housing 176 and the sleeve 177 are adjusted so that the amount of light entering the optical fiber is maximized, and the height of the ferrule 175 is also adjusted to set the point B to YA.
G weld.

Such a structure is not new. What is proposed by the present invention is that the grating 189 is provided at the tip of the optical fiber. This makes it possible to eliminate unnecessary light.

[Example of application to embodiment DIP package]
The present invention can of course be used for DIP packages. FIG.
It will be explained by. 16A is a sectional view, FIG. 16B is a rear view, and FIG. 16C is a perspective view. The housing 190 is
It is composed of a cap 200 and a package body 201. Inside the housing 190 is a lens holder-191, which holds a condenser lens 192.
A header 193 is provided behind the lens in the axial direction. A photodiode chip 194 is die-bonded to the header 193.

The electrodes of the photodiode chip 194 and the lead pins 195 are electrically connected by the wires 196. At the position opposite to the direction of the photodiode, the ferrule 19 holding the tip of the optical fiber 197 is held.
8 is plugged in. A grating 199 is also formed at the tip of this optical fiber. This also serves to reflect light of a certain wavelength and prevent it from reaching the photodiode.

[0106]

The present invention eliminates unnecessary light by providing an optical fiber grating filter inside the optical fiber instead of the multilayer film filter. Since an optical fiber grating filter is provided in addition to the wavelength demultiplexer, noise due to unnecessary light can be completely blocked.

The use of the fiber grating has its own advantages over the multilayer film. It means that the damping ratio can be easily reduced by the length of the grating. As described in the example, 1.3
When a grating with a length of 4 mm is made in the light receiving element for receiving μm light, 1.55 μm light is reduced to 10 ⁻² or less (−20d
B) Can be attenuated. If the length of the grating is 8 mm, it can be reduced to 10 ^-4 (-40 dB) or less. By increasing the length of the grating in this way, the damping ratio can be made as small as possible. Such a property does not depend on the wavelength. 4m for the light receiving element for receiving 1.55μm light
The attenuation ratio can be reduced to 1/100 by making a grating of m. If this is set to 8 mm, the damping ratio is 1/10.
It can be 000.

Optical fibers have been in existence from the beginning and have been
Since the strong light is emitted by the two-beam interference method, the grating can be easily lengthened by widening the exposure range. On the contrary, in order to reduce the damping ratio of the multilayer film, the number of multilayer films must be increased. Materials and production time will increase by that much, which will further increase the cost.

Since unnecessary light can be blocked by the grating filter, the conventional multilayer filter can be omitted. Since the part of the optical fiber is processed into a filter, the volume does not increase at all due to the presence of the filter. The required space can be reduced by the volume of the multilayer filter. It is possible to reduce component costs, assembly costs, and the like due to the multilayer filter. It is possible to provide a smaller and cheaper device as the ONU optical module.

[Brief description of drawings]

FIG. 1 is a principle diagram of a subscriber-side terminal for two-way optical communication.

FIG. 2 ONU using a mirror type wavelength demultiplexer and a coupler
Principle diagram of the module.

FIG. 3 is a principle diagram of an ONU module using a wavelength demultiplexer and a coupler using a quartz flat waveguide. (A) is a plan view.
(B) is AB sectional drawing.

FIG. 4 is a principle diagram of an optical fiber type ONU module using an optical fiber wavelength demultiplexer and an optical fiber coupler.

FIG. 5 is a vertical perspective view of a conventional semiconductor light receiving element module.

FIG. 6 is a principle diagram of an optical fiber grating filter.

FIG. 7 is a vertical cross-sectional view of an object in which an optical fiber having a grating is fixed to a ferrule.

FIG. 8 is a vertical perspective view of a semiconductor light receiving element module of the present invention.

FIG. 9 is a perspective view of an object provided with an optical fiber grating outside a module.

FIG. 10 is a front view of an FC connector and a ferrule for attaching a single mode fiber to an FC connector and attaching a ferrule extending from the FC connector to a module.

FIG. 11 is a schematic front view showing an embodiment in which a dummy fiber provided with a grating is fixed immediately before a ferrule and signal light is incident on a PD chip through the dummy fiber.

FIG. 12 is a schematic sectional view when the present invention is applied to a light-receiving element module using a butterfly type package.

FIG. 13 is a conventional module configuration diagram of fiber components in a simpler ONU module using 1.3 μm light for transmission and 1.55 μm light for reception.

FIG. 14 is a configuration diagram of an ONU module having the same function as in FIG. 13 configured by using the light receiving element of the present invention.

FIG. 15 is a vertical sectional view of a bell-shaped light receiving element module to which the present invention is applied.

FIG. 16 is a view showing a light receiving element accommodated in a DIP type package to which the present invention is applied. (A) is a sectional view,
(B) is a rear view and (c) is a perspective view.

FIG. 17 is a reflection spectrum diagram showing the relationship between the wavelength and the reflectance of a hydrogen-doped quartz fiber on which a 1.55 μm light reflecting grating is formed.

[Explanation of symbols]

 1 base station 2 subscriber side terminal 3 optical fiber 4 branching device 5 wavelength demultiplexer 6 analog PD 7 signal processing unit 8 TV 9 optical coupler 10 digital PD 11 signal processing unit 12 digital LD 13 telephone / facsimile 20 optical fiber 21 optical Connector 22 Collimator lens 23 Mirror type wavelength demultiplexer 24 Mirror type coupler 25 Multilayer film filter 26 Condenser lens 27 Digital PD 28 Digital LD 29 Condenser lens 30 Multilayer film filter 31 Condenser lens 32 Optical connector 33 Optical fiber 34 Single mode Fiber 35 Planar waveguide 36 Optical waveguide 37 Branching point 38 Optical waveguide 39 Optical waveguide 40 Optical coupler 41 Optical waveguide 42 Fiber approaching area of wavelength demultiplexer 43 Wavelength demultiplexer 44 Multilayer film filter 45 Digital PD 46 Digital LD 47 Condenser Les 48 end face 49 multilayer filter 50 analog output single-mode fiber 51 package 52 Si substrate 53 silica-based clad layer 60 input single-mode fiber 61 optical connector 62 optical fiber wavelength demultiplexer 63 optical connector 64 optical fiber coupler 65 branch 66 optical fiber 67 Optical Fiber 68 Multilayer Filter 69 Optical Connector 70 Digital PD Module 80 Optical Connector 82 Optical Fiber 83 Multilayer Filter 84 Optical Connector 85 Analog PD Module 86 Package 87 Anode Pin 88 Package Case Pin 89 Cathode Pin 90 Submount 91 Photodiode Tip 92 Ball lens 93 Cap with ball lens 94 Sleeve 95 Ferrule holder-96 hole 97 Ferrule 98 Single mode Fiber 99 Fiber tip 100 Core 101 Cladding 102 Grating part 103 Oblique polishing part 104 Bend limiter 109 Fiber grating filter 110 PD module 111 Optical fiber 112 Single mode fiber 113 Ferrule 114 Ceramic capillary 115 FC connector 116 Zirconia ferrule 117 Receptacle type light receiving module 118 Fiber code 119 Ferrule 120 Single mode fiber 121 Housing 122 Fitting cap nut 123 Key 124 Lens holder-125 Lens 126 Fiber holder-127 Dummy fiber 128 Housing 129 Flange part 130 Set screw hole 131 Male screw part 132 Sleeve 133 Package 134 sub Und 135 PD chip 136 Lead pin 137 Wire 138 Cap 139 Sealing window glass 140 Butterfly type light receiving element 141 Package 142 Lead pin 143 Lens holder-144 lens 145 hole 146 Ferrule 147 Optical fiber 149 Grating part 150 Chip carrier 151 Photo diode chip 152 Optical connector 153 optical fiber wavelength demultiplexer 154 optical fiber 155 optical fiber 156 optical connector 157 optical fiber 158 LD module 159 multilayer filter 160 optical connector 161 PD module 162 fiber 163 optical connector 164 optical fiber coupler 165 optical fiber 166 optical fiber 168 optical connector 171 LD module 173 PD module 174 Optical Fiber 175 Ferrule 176 Housing 177 Sleeve 178 Header 179 Lead 180 Mount 181 Photodiode chip 182 Wire 183 Cap 184 Window 185 Aperture 186 Condensing lens 187 End face 188 End face 189 Grating 190 Housing 193 Header lens 192 Lens holder- Diode chip 195 Lead pin 196 Wire 197 Optical fiber 198 Ferrule 199 Grating 200 Cap 201 Package 202 Through hole

Claims (5)

[Claims] 1. A photodiode chip for converting an optical signal into an electric signal, a unit for extracting the electric signal to the outside, a unit for supporting the photodiode chip and the unit for extracting the electric signal to the outside, and an optical signal from the outside. In a semiconductor photodetector consisting of a transmitting optical fiber and its support, a fiber grating filter that selectively reflects light of a desired wavelength is provided in a part of the optical fiber inside the support. A semiconductor light receiving element characterized by. 2. The semiconductor light receiving element according to claim 1, wherein the fiber grating filter is formed in a part of the silica-based single mode fiber. 3. The photodiode chip is InGaAs
Alternatively, the semiconductor light receiving element according to claim 1, further comprising an InGaAsP light receiving layer. 4. The wavelength of light that is selectively reflected is 1.3 μm.
The semiconductor light receiving element according to claim 2 or 3, wherein the band is a band or a band of 1.55 μm. 5. A package having a lead pin, a submount fixed to the surface of the package, a photodiode chip fixed to the package via the submount for converting an optical signal into an electric signal, and an electrode of the photodiode chip, A wire that connects the submount electrode and the lead pin, a cap that has a light transmitting window or a condenser lens and is hermetically fixed to the package in a state filled with an inert gas, and a single mode fiber that transmits an optical signal,
It consists of a ferrule that holds the tip of the single mode fiber, a ferrule holder that holds the ferrule and is fixed to the package, and a fiber grating that reflects light of a specific wavelength formed in the single mode fiber inside the ferrule. A semiconductor light receiving element characterized by the above.