JPH0457418A - Method and apparatus for two-way optical communication - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to two-way communication that connects two stations with a single optical fiber and uses optical signals of varying wavelengths, particularly high efficiency, The present invention relates to a bidirectional optical communication method and device that realizes low-cost, long-distance transmission.

[Prior art] Multiple optical signals with different wavelengths (λ1
．． Bidirectional wavelength multiplexing transmission, which transmits λ2..., λn) in both directions, is an extensible system.

It is expected to be economical and flexible.

FIG. 5 shows an example of the configuration of a conventional bidirectional wavelength division multiplexing transmission system. This is because one optical fiber 4 connects stations 8 and 9, and the wavelength λ1. The optical signal of λ2 is transmitted in both directions. That is, from the station 8 side, the wavelength λ is transmitted from the optical transmitter 1.
1 signal to the optical multiplexing/demultiplexing section 3. The signal is sent to the station 9 via the optical fiber 4, demultiplexed by the optical multiplexer 7, and received by the optical receiver 6.

Conversely, from the station 9 side, an optical signal of wavelength λ2 is sent from the optical transmitter 5 to the optical multiplexer/demultiplexer 7. Send it to the station 8 side via the optical fiber 4,
The configuration is such that the optical multiplexer/demultiplexer 3 demultiplexes the signals and the optical receiver 2 receives the signals.

[Problem to be solved by the invention] In conventional bidirectional transmission systems, wavelengths λ1 and λ2 are usually 1
．． A 3 μm band and a 1.55 μm band are used, and the optical fiber 4 is a single mode fiber. If you try to secure a span distance of about 1 in 10 using this method,
Since the optical output of current semiconductor lasers is on the order of several mW, the coupling loss between the semiconductor laser and the optical multiplexer/demultiplexer, the insertion loss of the optical multiplexer/demultiplexer, the coupling loss between the optical multiplexer/demultiplexer and the light receiving element, and the optical multiplexer/demultiplexer The coupling loss between the optical fiber and the optical fiber must be constructed using the best current technology.

In other words, there is almost no loss margin, which not only reduces the cost of parts, but also the processing and assembly of parts.

Moreover, the implementation cost was also very high. Furthermore, for the above reasons, it has also been difficult to increase the span distance M beyond the above value. Furthermore, since there is almost no loss margin,
It was also difficult to construct a reliable system.

The purpose of the present invention is to eliminate the drawbacks of the prior art described above, to realize an economical and highly reliable system with a simple configuration,
Another object of the present invention is to provide a bidirectional optical communication method and device that can extend the span distance.

[Means for Solving the Problems] The two-way optical communication method of the present invention provides communication between two stations A and 8.
The connection is made with a main optical fiber, and from station A, the wavelength is at least λ.
In the bidirectional wavelength multiplexing transmission method, in which information is loaded on an optical signal of wavelength λ1 and transmitted from station B, and information of an optical signal of at least wavelength λ2 is loaded and transmitted from station B, station A11ll transmits the optical signal of at least wavelength λ1 to a rare earth element. The optical signal is amplified and transmitted by passing through the rare earth element-doped optical transmission line, and at station B, information is added to the optical signal of wavelength λ2 that excites the rare earth element-doped optical transmission line and transmitted (Claim 1). Here, the rare earth element-doped optical transmission line may be an optical fiber, a leading waveguide, or the like.

Specifically, the wavelength λ1 is 1.3 μm band,
A bidirectional optical communication method (Claim 2) using a 0.8 μm band as the wavelength λ2 and using an Nd-doped optical transmission line as a rare earth element-doped optical transmission line, and a 1.5 μm band as the wavelength λ1.
There is a bidirectional optical communication method (claim 3) that uses the m-band, the 1.48 μm band as the wavelength λ2, and uses an Nr-doped optical transmission line as the rare earth element-doped optical transmission line. in this case,
Station A (Claim 7) multiplexing at least two 1.3 μm band optical signals from Fl and sending them to station BfFJ through a rare earth element-doped optical transmission line (Claim 7);
Multiplexing at least two μm band optical signals and transmitting them to the station B side through a rare earth element-doped optical transmission line (Claim 8)
is also free.

As another form, information is further transmitted from station B on an optical signal of wavelength λ3, and at station A, the optical signal of wavelength λ3 is amplified through another rare earth element-doped optical transmission line. There is a bidirectional communication method in which light is received (claim 4). In this case, a 1.5 μm band is used as the wavelength λ3, and Nr is used as the two rare earth element-doped optical transmission lines.
It is possible to use an optical transmission line doped with iron and Nd (claims 5 and 6).

The two-way optical communication device of the present invention provides one communication between two stations A and B.
Connected by two optical fibers, station A has a wavelength of at least λ
In a bidirectional wavelength division multiplexing transmission device, in which information is loaded on an optical signal of wavelength λ2 and sent out from station B, information of an optical signal of at least wavelength λ2 is loaded and transmitted from station A.
an optical transmission section that sends out an optical signal of wavelength λ1; a rare earth element-doped optical transmission line that has a function of amplifying the optical signal of wavelength λ1;
an optical receiving section for receiving the optical signal of 2, and an optical branching section;
On the station B side, there is an optical transmitter with a wavelength λ2 for exciting the rare earth element-doped optical transmission line and for information transmission, and an optical transmitter with a wavelength λ2.
According to a ninth aspect of the present invention, the optical receiver includes an optical receiving section for receiving one optical signal and an optical multiplexing/demultiplexing section (claim 9).

In this case, the station B 111l is provided with an optical transmitter that transmits information on an optical signal of wavelength λ3, and the station A side is equipped with an optical transmitter that is excited by the optical signal of wavelength λ2 and amplifies the optical signal of wavelength λ3. Rare earth element-doped optical transmission line and this amplified wavelength λ
It is preferable to provide an optical receiving section including a light receiving element that receives the optical signal of No. 3.

[From the working station A, the optical signal with the wavelength λ1 passes through the rare earth element-doped optical transmission line to be sufficiently amplified, and then is sent to the station B side via the optical branching section and the optical fiber. Therefore, it is necessary to provide a large loss margin for the coupling loss of the optical signal of wavelength λ1 between the semiconductor laser and the rare earth element-doped optical transmission line, the insertion loss of the optical branch, and the coupling loss between the optical branch and the optical fiber. can. Therefore, it can be realized with simple implementation and cost reduction can be achieved. The span distance can also be expanded.

Another advantage is that the light-emitting element for excitation of the rare-earth element-doped optical transmission line on the station B side has currently been developed with a high output (about 100-odd tw), and this light-emitting element can be used as a light source for information transmission. By using the same as a light source for excitation of a rare earth element-doped optical transmission line, a large loss margin can be obtained and the span distance can be extended.

[Embodiment] FIG. 1 shows an embodiment of the bidirectional optical communication method and apparatus of the present invention.

The optical transmitter 1 of the station 81111 includes a light emitting element 10 that sends out an optical signal of wavelength λ1, and a rare earth element-doped transmission line 15 that amplifies the optical signal.

The optical transmitter 5 of the station 9 is composed of a light emitting element (wavelength λ2) for exciting the rare earth element-doped transmission line 15, and this optical signal carries an information signal. The signal is sent to the station 8 via the optical fiber 4. The light is then branched by the optical branching section 16, and a portion is sent to the optical receiving section 2 to reproduce the information signal. Most of the rest is rare earth element added transmission #1
As it propagates through 15, it is absorbed by rare earth ions, thereby forming a population inversion, thereby amplifying the optical signal of wavelength λ1. Note that an information signal is also carried on the optical signal of wavelength λ1.

A concrete example of the embodiment shown in FIG. 1 is shown in FIG.

The wavelength λ1 is 1.3μ (1.32μ in this example).
The information signal is added to the optical signal of the semiconductor laser 10 and sent from the station 8 to the station 9. In this example, an Nd-doped optical transmission line (for example, Zr-Ba-La-Al-Nd system or optical waveguide #1) is used as the rare earth element-doped transmission line 15, and the optical signal of wavelength λ1 is amplified. let

That is, the optical signal with a wavelength of 1.32 μm from the semiconductor laser 10 is transmitted through Nd-doped optical transmission F! It is amplified by propagating through the optical branching section 16. Optical fiber 4-beam multiplexer/demultiplexer 1
7 as shown by the arrow 18, and the interference film filter 2
By passing through 0, the purity of the wavelength can be further improved,
The information signal is reproduced by the light receiving element 22.

From the station 9 side, an information signal is added to the optical signal of the diagonal semiconductor laser 21 (wavelength λ2 = 0.81 μm band) excited by the Nd-doped optical transmission path 15, and transmitted through the optical multiplexer/demultiplexer 17 and the optical fiber. 4 to the station 8 side.

Then, a part of the optical signal is branched at the optical branching section 16, and
The light enters the interference film filter 14 as indicated by an arrow 13. This interference film filter 14 has a function of passing only an optical signal with a wavelength λ2=0.81 μm and blocking an optical signal with a wavelength λ1 of 1.32 μm.

The light receiving element 11 reproduces an information signal from the optical signal having the wavelength λ2 that has passed through the interference film filter 14.

In addition, most of the remaining optical signals with the wavelength λ2 are transmitted to the optical branching section 16.
By propagating through the Nd-doped optical path 15,
It is possible to amplify an optical signal with a wavelength λ1=1.32 μm propagating from the opposite direction.

In other words, high-output optical signals can be transmitted bidirectionally from both the station 8 side and the station 9 side, allowing for a large individual loss margin.

Positional tolerance accuracy during processing and mounting can be relaxed.

FIG. 3 shows another embodiment of the bidirectional optical communication method and apparatus of the present invention.

This uses an E-doped optical transmission line as a rare earth element-doped optical transmission line, and the wavelength of the optical signal to be amplified is in the 1.5 μm band (
In this case, 1.54 μm was used), and 1.48 μm was used as the wavelength of the excitation optical signal.

By using Er as a transmission line doped with rare earth elements,
Optical signals in the wavelength band of 1.5 μm can be amplified. The wavelength of the excitation light source is 1.48 μm or 0.98 μm.
However, the branching ratio of the optical branching section 16 is 50:1.20:1゜1.
Values such as 0:1.5:1 can be used. The value of this branching ratio is the optical output of the semiconductor laser 21, the light receiving element 1
It can be set in consideration of the relationship between the light receiving sensitivity of No. 1, the length of the rare earth element doped transmission line, the rare earth element doped concentration, and the like. In addition, the wavelength 1.3 μm band is a wavelength of 1.28 to 1.35 μm.
The wavelength range of 1.5 μm refers to the wavelength range of 1.5 to 1.5 μm.
The range of 58 μm band is 0.8 μm wavelength band, which is 0.78~
It represents a range of 0.83 μm.

FIG. 4 shows still another embodiment of the bidirectional wavelength optical communication method and apparatus of the present invention. This is station 9fFI
From this, optical signals with wavelengths λ2 = 1.55 μm and λ3, 0.8 μm are sent out with information signals on them, and from the station 8 side, optical signals with wavelengths λ1, 1.3 μm are sent out with information signals on them. This is what I did.

Here, on the station 8 side, in addition to providing the Nd-doped optical path 15 for amplifying the information signal of the optical signal with the wavelength λ1 = 1.3 μI, there is also an optical path 15 for amplifying the optical signal with the wavelength λ3 of 1.55 μm. An E doped light transmission line 23 is provided for inputting light into the light receiving element 24.
As a light source for exciting the wavelength λ2 = 0.8 μm
A semiconductor laser 21 is used.

Note that the Er-doped light-speed transport path 23 includes Ge and P.

A quartz optical fiber containing dopants such as AI, Yb, Ti, etc., a quartz-based optical waveguide, and as mentioned above, Zr
-Ba-La-Al-Nd-based optical fiber doped with E' or an optical waveguide may be used.

In addition, in FIG. 4, a part of the optical fiber 4 contains Nd and E.
A material co-doped with may also be used.

In this way, the wavelengths λ1·1.3 μt and λ3·1.
It is possible to commonly amplify optical signals of 55 μm.

As described above, the number of wavelengths to be multiplexed may be increased beyond 2 or 3.

For example, in FIG.
range)) may be multiplexed and transmitted.

Alternatively, in FIG. 3, several waves to several dozen waves (in the range of 1.52 to 1.56 μm) of 1.5 μm band optical signals may be multiplexed and transmitted from the station 8 side.

The station 91Fl is configured to separate the optical signals of different wavelengths using an optical multiplexer/demultiplexer.

Alternatively, a tuner pull filter may be inserted in front of the light-receiving element 22, and by selectively tuning the multiplexed optical signals with different wavelengths, the light-receiving element may receive them.4Similarly, Also in Figure 4, station 9
Optical signals in the 1.55 μI band may be multiplexed from several waves to several tens of waves and transmitted from the side, a tuner pull filter may be inserted in front of the light receiving element 24 of the station 8, and selective reception may be performed as described above. It goes without saying that the optical fiber 4 may partially include an optical fiber doped with a rare earth element.

As described above, since a loss margin of at least 10 dB can be secured compared to the conventional method, the assembly, processing, and mounting precision of each optical component part can be significantly relaxed.

Therefore, it is possible to realize an economical and highly reliable system with a simple configuration. It is also possible to extend the span distance.

[Effects of the Invention] As described above, according to the present invention, the loss margin can be increased by at least 10 dB compared to the conventional method, so the assembly, processing, and mounting accuracy of each optical component can be significantly relaxed. be able to.

Therefore, it is possible to realize an economical and highly reliable system with a simple configuration. It is also possible to extend the span distance.

[Brief explanation of the drawing]

1, 2, 3, and 4 are diagrams showing different embodiments of the bidirectional optical communication method and device of the present invention, and FIG.
The figure shows an example of the configuration of a conventional two-way multiplex transmission system. In the figure, 1 is an optical transmitter, 2 is an optical receiver, 3 is an optical multiplexer/demultiplexer,
4 is an optical fiber, 5 is an optical transmitter, 6 is an optical receiver, 7 is an optical multiplexer/demultiplexer, 8 is a station A, 9 is a station B, 10 is a semiconductor laser,
11 is a light receiving element, 14 is an interference film filter, 15 is a rare earth element-doped optical transmission line, 16 is an optical branching section, 17 is an optical multiplexing/demultiplexing section, 21 is a semiconductor laser, 22 is a light receiving element, 23 is an Er-doped optical transmission line , 24 is a light receiving element, and 25 is a semiconductor laser.

Claims (1)

[Claims] 1. Two stations A and B are connected by one optical fiber, and station A sends out an optical signal with at least wavelength λ1 loaded with information, and station B sends out an optical signal with at least wavelength λ2. In a bidirectional wavelength multiplexing transmission method in which information on an optical signal is loaded and transmitted, station A
At the station B, the optical signal of at least wavelength λ1 is passed through a rare earth element-doped optical transmission line to be amplified and sent out, and at station B, information is added to the optical signal of wavelength λ2 that excites the rare earth element-doped optical transmission line. A two-way optical communication method characterized by transmitting. 2. The wavelength λ1 is 1.3 μm band, and the wavelength λ2 is 0.
2. The bidirectional optical communication method according to claim 1, wherein an optical transmission line doped with Nd is used as the rare earth element-doped optical transmission line using an 8 μm band. 3. 1.5 μm band as wavelength λ1, 1.5 μm band as wavelength λ2.
Using the 48 μm band, Nr is used as a rare earth element doped optical transmission line.
Claim 1 characterized in that an optical transmission line doped with is used.
The bidirectional optical communication method described. 4. Furthermore, station B transmits information on an optical signal of wavelength λ3, and station A receives this optical signal of wavelength λ3 after amplifying it through a rare earth element-doped optical transmission line different from the above. The bidirectional optical communication method according to claim 1. 5. The bidirectional optical communication method according to claim 4, wherein a 1.5 μm band is used as the wavelength λ3. 6. Nr and N as the two rare earth element-doped optical transmission lines
5. The bidirectional optical communication method according to claim 4, wherein an optical transmission line co-doped with d is used. 7. The bidirectional optical communication method according to claim 2, wherein at least two 1.3 μm band optical signals are multiplexed from the station A side and sent to the station B side through a rare earth element-doped optical transmission line. 8. The bidirectional optical communication method according to claim 3, wherein at least two 1.5 μm band optical signals are multiplexed from the station A side and sent to the station B side through a rare earth element-doped optical transmission line. 9. Connect two stations A and B with one optical fiber, and station A sends out information on an optical signal with at least wavelength λ1, and station B sends out information on an optical signal with at least wavelength λ2. In a two-way wavelength division multiplexing transmission device, station A
On the side, there is provided an optical transmission section that transmits at least an optical signal of wavelength λ1, a rare earth element-doped optical transmission line having a function of amplifying the optical signal of wavelength λ1, an optical reception section that receives an optical signal of wavelength λ2, and An optical branching section is provided, and on the station B side, an optical transmitting section with a wavelength λ2 for exciting the rare earth element-doped optical transmission line and for information transmission, and an optical receiving section for receiving an optical signal with a wavelength λ1. , and an optical multiplexing/demultiplexing section. 10. The station B side is provided with an optical transmitter that transmits information on an optical signal of wavelength λ3, and the station A side is equipped with an optical transmitter that is excited by the optical signal of wavelength λ2 and amplifies the optical signal of wavelength λ3. 10. The bidirectional optical communication device according to claim 9, further comprising an optical receiver comprising a rare earth element-doped optical transmission line and a light receiving element for receiving the amplified optical signal of wavelength λ3.