JP2000231027A - Mode conditioner - Google Patents

Abstract

(57) [Problem] To provide a low-cost mode conditioner capable of reducing or eliminating the influence of DMD which is a problem when transmitting laser light through a multi-mode optical fiber. SOLUTION: A dual optical connector 20 detachably fitted to an optical transceiver 30 having a laser light source, and a dual optical connector 21 connected to a multimode optical fiber for transmission.
And a patch cord-type mode conditioner composed of the optical fibers 11 and 12 connecting the two optical connectors 20 and 21, the mode conditioning is performed by using the ferrule 25 eccentric to the dual optical connector 21. Therefore, high-speed optical data transmission using a multi-mode optical fiber can be realized at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a patch cord type mode conditioner.

[0002]

2. Description of the Related Art A patch cord type mode conditioner is used when an optical transmitter having a laser light source and an optical device are connected by an optical fiber cable. The mode conditioner includes a first optical connector detachably fitted to an optical transmitter, a second optical connector connected to a multi-mode optical fiber for transmission, and an optical fiber connecting both optical connectors. It is composed of

[0003] The refractive index distribution of the core of a multimode optical fiber used for a mode conditioner, particularly a graded index type multimode optical fiber (hereinafter, referred to as "MMF"), is degraded by a delay difference between modes (mode dispersion). ) Is designed and manufactured to draw a precise quadratic curve from the center outward.

However, MMs manufactured mainly in North America
It is known that F has an incomplete refractive index distribution as shown in FIG.

FIG. 7 is a graph showing the refractive index distribution of the MMF. The horizontal axis represents the distance from the axis, and the vertical axis represents the refractive index.

[0006] Such a refractive index distribution may lead to deterioration of transmission performance, but until now MMF has been generally used for transmission of several hundred Mb / s or less. In addition, since the light source used for the transmission is often a light emitting diode (hereinafter, referred to as “LED”), it has not been a serious problem.

On the other hand, recently, M
There has been a demand for using the MF for very high-speed transmission in the Gb / s class, and there is a problem how to suppress transmission degradation while using an optical fiber having a refractive index distribution as shown in FIG.

In an MMF having a refractive index distribution as shown in FIG. 7, light propagates faster than the core peripheral portion because the refractive index is small near the center of the core. Therefore, when an optical pulse is transmitted, the pulse is dispersed due to a delay difference between light traveling near the center of the core and light traveling around the core. Delay which causes such dispersion
e Delay (hereinafter referred to as "DMD"). Such a phenomenon is likely to occur when light with high parallelism is concentrated near the center of the optical fiber core.

Optical transmitters and receivers have different specifications depending on the type of optical fiber and the wavelength of the light source, even if the transmission speed is the same.

However, in recent years, for example, in order to reduce the cost and simplify the handling, an optical transceiver having a 1300 nm band laser light source is changed to a single mode optical fiber (hereinafter, “SMF”).
) And MMF.

However, since the optical transceiver that can be connected to the SMF has a structure in which light with high parallelism is concentrated and output at the center of the core, the optical transceiver can be connected to the MMF. We need to think about ways to avoid the DMD problem.

One method of avoiding the DMD problem is mode conditioning by offset light incidence.

FIG. 8 is a block diagram showing a conventional patch code type mode conditioner.

The patch cord is a jumper cord connecting a short distance from a transmission device such as the LAN device 31 to the optical fiber termination panel (patch panel) 24.

FIG. 9 is an enlarged view of the inside (only the transmission side) of the optical fiber connection section at a substantially intermediate point of the mode conditioner shown in FIG.

The above-described conventional mode conditioner has a configuration in which the two double optical connectors 20 and 21 are connected by an optical fiber cord, and has an optical fiber cord connecting portion 10 in the middle. Only the optical fiber coupled to the transmitting side of the optical transceiver 30 is the SMF 11, and the other optical fibers are
MF12. On the transmission side of the connection unit 10, the SMF 11 and the MMF 12 are fusion-connected so that the centers of the cores 15 and 16 are shifted. From the optical transceiver 30 to the SMF 11
Is incident on the MMF 12 while avoiding the center of the core, that is, the mode is conditioned only on the higher-order mode. The light once shifted from the center rarely enters the low refractive index portion at the center of the core 16 during propagation, so that the influence of the DMD can be avoided.

In this mode conditioner, there is no problem even if the transmission fiber used is an MMF having no abnormal refractive index distribution as shown in FIG. In addition, since the receiving side does not need mode conditioning, the MMFs 12 may be fused together without shifting them at the connection unit 10 or optical connectors may be connected to both ends of one MMF like a normal optical jumper. do it.

[0018]

However, in the above-mentioned conventional technique, the SMF 11 and the MMF 12 are connected to the core 1.
It is characterized in that the fusion splicing is performed with the centers of 5 and 16 shifted. However, such a patch cord has a problem in that the production cost is high.

First, it takes time to connect the optical fiber. With the latest fully automatic fusion splicer, splicing of fiber strands alone (fusion) has become less difficult than before, but nevertheless this operation must be performed carefully by a skilled operator. Furthermore, this kind of fusion work is a work that differs from normal fusion work in that the center is precisely shifted and fused.
It is not easy to manufacture stably so that this deviation is constant.

Further, after the fusion of the fiber wires, it is necessary to connect reinforcing materials such as Kevlar and to cover and protect the connecting portions. Most of these operations need to be done manually, which is very time-consuming.

Further, the inspection after fusion of the optical fibers cannot be evaluated only by simple measurement of the passage loss or the like, and it is necessary to measure the mode distribution and the like in the multi-mode fiber. There was a problem that would be.

Accordingly, an object of the present invention is to solve the above-mentioned problems and to reduce and eliminate the influence of DMD, which is a problem when transmitting laser light through a multimode optical fiber,
Another object of the present invention is to provide a low-cost mode conditioner.

[0023]

In order to achieve the above object, a mode conditioner according to the present invention comprises a first optical connector detachably fitted to an optical transmitter having a laser light source;
In a patch cord type mode conditioner including a second optical connector connected to a multi-mode optical fiber for transmission and an optical fiber connecting both optical connectors, the optical fiber is a single mode type, The fiber insertion hole of the ferrule of the second optical connector is eccentric from the center of the ferrule.

Also, the mode conditioner of the present invention
A first detachably fitted to an optical transmitter having a laser light source;
And a second optical connector connected to the multi-mode optical fiber for transmission, and an optical fiber connecting the two optical connectors, wherein the optical fiber is a multi-mode. It is a mode type, in which the fiber insertion hole of the ferrule of the first optical connector is eccentric from the center of the ferrule.

In addition to the above configuration, the mode conditioner of the present invention has a first optical connector, a second optical connector, and an optical fiber that couples both optical connectors, each of which has a double structure, and is connected to an optical receiver. It is preferable that the optical fiber on the side to be connected is a multimode type and can be easily attached to and detached from the optical transmitter integrated with the optical receiver.

According to the present invention, the mode conditioning is performed by using the eccentric ferrule as the ferrule of the optical connector. Therefore, the operation of fusing by shifting the center precisely or the reinforcing material such as Kevlar after the fusion of the fiber element wire is performed. This eliminates the need for processing such as connection and connection / covering / protection of the connection portion, and realizes high-speed optical data transmission using a multimode optical fiber at low cost.

[0027]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the mode conditioner of the present invention.

The mode conditioner includes a double optical connector 20 as a first optical connector detachably fitted to an optical transceiver 30 having a laser light source, and a double optical connector 20 at one end (left end in the figure). And a second optical connector connected to the other end (the right end in the figure) of the two optical fibers 11 and 12 and the parallel optical fiber cord composed of a multi-mode optical fiber MMF12 and a single-mode optical fiber SMF11 for transmission. Double optical connector 21 as
It is composed of

This mode conditioner is a patch cord type mode conditioner for coupling to an integrated optical transceiver 30. The optical fiber insertion hole 17 of the ferrule 25 of the dual optical connector 21 is located at the center of the ferrule 18. It is more eccentric than Lf.

The optical fiber connected to the transmitting side of the optical transceiver 30 is the SMF 11, and the optical fiber connected to the receiving side is the MMF 12. An optical connector coupling adapter 2 is attached to the optical connector 22 of the transmission optical fiber cord.
Only the ferrule 25 on the transmission side of the dual optical connector 21 connected via the third optical connector 21 is an eccentric ferrule having an eccentric optical fiber insertion hole 17.

FIG. 2 is an enlarged view of the transmitting side optical connector coupling portion in the optical connector coupling adapter of the patch panel shown in FIG. FIG. 3 is an enlarged view near the coupling portion of the optical fiber shown in FIG.

In the ferrule 25 on the side of the optical transceiver (the left side in the figure), the optical fiber insertion hole 17 is shifted from the center Lf of the ferrule 18 by about 20 μm, and the SMF 11 is inserted.
Fixed and normal polished. The ferrule 18 on the transmission optical fiber cord side is a normal ferrule without eccentricity, and is mated with a ferrule 25 on the optical transceiver side by a split sleeve 26 in the adapter 23 for coupling an optical connector. The optical signal transmitted from the optical transceiver 30 by the SMF 11 is approximately 20 μm from the center of the MMF 19 of the transmission optical fiber cord due to the eccentricity of the ferrule 25.
The light enters a position shifted by m. For this reason, light does not enter the low-refractive-index portion at the center of the MMF 19, or even if it enters, the amount becomes very small, so that deterioration of transmission characteristics due to band deterioration caused by DMD can be avoided.

As described above, according to the present invention, if only one of a plurality of ferrules is replaced with an eccentric ferrule, a mode conditioner can be manufactured in exactly the same process as that for manufacturing other ordinary patch cords. It is possible, and it is not necessary to use a special fusion technique or a complicated process as in the related art. The DMD removal effect can be expected to be exactly the same as the conventional technology. As described above, the cost of the mode conditioning patch cord can be significantly reduced.

FIG. 4 is a block diagram showing another embodiment of the mode conditioner of the present invention. FIG. 5 is an enlarged view of the transmitting side of the optical connector coupling section of the optical transceiver shown in FIG. FIG. 6 is an enlarged view of the vicinity of the coupling portion of the optical fiber shown in FIG.

Similar to the mode conditioner shown in FIG. 1, a patch cord having a double optical connector 20 and 21 attached to both ends of a parallel optical fiber cord for coupling to an integrated optical transceiver 30 is used. are doing.

The difference from the mode conditioner shown in FIG. 1 is that the optical fibers connected to the transmitting side and the receiving side of the optical transceiver 30 are both the MMF 12, and the optical connector (receptacle) of the optical transceiver 30. The only difference is that only the ferrule 27 on the transmitting side of the dual optical connector 20 connected to the optical connector 20 is an eccentric ferrule having an eccentric optical fiber insertion hole 28.

The transmitting optical system of the optical transceiver is a ferrule 2
9 and the optical fiber 32 in the ferrule 29 is SMF. The ferrule 27 of the optical connector fitted to the ferrule 29 has an optical fiber insertion hole 28 shifted from the center Lg of about 20 μm, and the MMF 12 is inserted and fixed and polished normally.

The ferrule 29 of the optical transceiver 30 and the ferrule 27 of the patch cord dual optical connector 20 are butted by a split sleeve 33 in the optical connector of the optical transceiver. The optical signal output from the optical transceiver 30 is incident on the patch cord at a position shifted from the center of the MMF 12 due to the eccentricity of the ferrule 27. Therefore, MMF12
No light enters the low-refractive-index portion at the center of the light-emitting device, or even a very small amount of light enters the light-receiving portion, so that deterioration in transmission characteristics due to band deterioration caused by DMD can be avoided.
Note that the split sleeve 33 may be provided on the double optical connector 20 side instead of the optical transceiver 30 side.

Also in this embodiment, if only one of a plurality of ferrules is replaced with an eccentric ferrule, a mode conditioner can be manufactured in exactly the same process as that for manufacturing a normal patch cord. Therefore, the cost of the mode conditioning patch cord can be significantly reduced. In the present embodiment, the transmission side optical system of the optical transceiver has a ferrule. However, the present invention is not limited to this, and the same effect can be expected in the case of an optical transceiver without a ferrule.

[0041]

In summary, according to the present invention, the following excellent effects are exhibited.

It is possible to reduce the cost of a mode conditioner capable of reducing and eliminating the influence of DMD, which is a problem when transmitting laser light through a multi-mode optical fiber.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a mode conditioner according to the present invention.

FIG. 2 is an enlarged view of a transmitting side optical connector coupling portion in the optical connector coupling adapter of the patch panel shown in FIG.

FIG. 3 is an enlarged view near a coupling portion of the optical fiber shown in FIG. 2;

FIG. 4 is a block diagram showing another embodiment of the mode conditioner of the present invention.

FIG. 5 is an enlarged view of a transmitting side of an optical connector coupling section of the optical transceiver shown in FIG.

FIG. 6 is an enlarged view near a coupling portion of the optical fiber shown in FIG.

FIG. 7 is a diagram showing a refractive index distribution of MMF.

FIG. 8 is a configuration diagram showing a conventional patch cord type mode conditioner.

FIG. 9 is an enlarged view of the inside of the transmission side of the optical fiber connection part at a substantially intermediate point of the mode conditioner shown in FIG. 8;

[Explanation of symbols]

 Reference Signs List 11 SMF (single mode optical fiber) 12 MMF (multimode optical fiber) 20 double optical connector (first optical connector) 21 double optical connector (second optical connector) 25 ferrule 26 split sleeve 30 optical transceiver

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takehiko 5-1-1, Hidaka-cho, Hitachi-shi, Ibaraki F-term in Opto-Systems Research Laboratory, Hitachi Cable, Ltd. 2H037 AA01 BA35 DA06 DA31 2H047 KA04 KB03 LA24 RA00 TA00

Claims (3)

[Claims] 1. A first optical connector detachably fitted to an optical transmitter having a laser light source, a second optical connector connected to a multi-mode optical fiber for transmission, and both optical connectors are coupled. A patch cord type mode conditioner comprising an optical fiber, wherein the optical fiber is a single mode type, and a fiber insertion hole of a ferrule of the second optical connector is eccentric from a center of the ferrule. Conditioner. 2. A first optical connector detachably fitted to an optical transmitter having a laser light source, a second optical connector connected to a multi-mode optical fiber for transmission, and both optical connectors. A patch cord type mode conditioner comprising an optical fiber, wherein the optical fiber is a multi-mode type, and a fiber insertion hole of a ferrule of the first optical connector is eccentric from a center of the ferrule. Conditioner. 3. An optical fiber connecting the first optical connector, the second optical connector, and the two optical connectors, each of which has a double structure, and the optical fiber connected to the optical receiver is a multimode optical fiber. The mode conditioner according to claim 1, wherein the mode conditioner is a mold and can be easily attached to and detached from an optical transmitter integrated with the optical receiver.