JP3680565B2 - Mode conditioner - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mode conditioner for connecting a single mode optical fiber and a multimode optical fiber.
[0002]
[Prior art]
The refractive index profile of the core of a grating index type multimode optical fiber (hereinafter referred to as “MMF”) decreases with a quadratic curve from the center to the outside in order to suppress band degradation (mode dispersion) due to the delay difference between modes. Designed and manufactured to do.
[0003]
However, it is known that some MMFs manufactured in North America have an incomplete refractive index distribution as shown in FIG.
[0004]
FIG. 6 is a diagram showing a refractive index distribution of a multimode optical fiber having a low refractive index portion at the core central portion. In the figure, the horizontal axis indicates the distance from the axis (center axis), and the vertical axis indicates the refractive index.
[0005]
Although the refractive index distribution as shown in FIG. 6 may lead to deterioration in transmission performance, MMF has been generally used for signal transmission with a transmission speed of several hundred Mb / s or less. Further, since the light source used for signal transmission is often a light emitting diode, it has not been a big problem.
[0006]
By the way, in recent years, there has been a demand for using MMF that has already been laid for very high-speed signal transmission of about Gb / s, and how transmission degradation occurs using an optical fiber having a refractive index distribution as shown in FIG. The problem is whether to suppress this.
[0007]
In an MMF having a refractive index distribution as shown in FIG. 6, the light propagates faster than the periphery of the core because the refractive index is small near the core center. When a pulse is transmitted to such an MMF, the pulse is dispersed due to the delay difference between the light propagating in the vicinity of the core center and the light traveling in the periphery of the core. A delay that causes such dispersion is called Differential Mode Delay (hereinafter referred to as “DMD”). Such a phenomenon is likely to occur when light having a high degree of parallelism is concentrated at the center of the optical fiber core.
[0008]
The optical transceiver is different from the type of optical fiber used and the wavelength of the light source even when the transmission speed is the same. However, in recent years, in order to reduce costs and simplify handling, for example, an attempt has been made to connect an optical transceiver having a 1300 nm band laser light source to both a single mode optical fiber (hereinafter referred to as “SMF”) and an MMF. It has been.
[0009]
However, since the optical transceiver that can be connected to the SMF has a structure that concentrates and outputs light with a high degree of parallelism at the center of the core, in order to enable connection to both the SMF and the MMF, there is a problem with the MMF DMD. It is necessary to think about how to avoid.
[0010]
One method for avoiding the DMD problem is mode conditioning by offset light incidence.
[0011]
FIG. 7 is a diagram showing a conventional example of a patch cord type mode conditioner.
[0012]
The patch cord is a jumper cord that connects a short distance from a transmission device such as a LAN to the optical fiber termination panel.
[0013]
The patch cord shown in FIG. 2 is detachably connected to a duplex optical connector 20 detachably connected to each terminal of an optical transceiver having a laser light source and an optical connector coupling receptacle 23 of the patch panel 24. The optical fiber connector 21 includes an SMF 11 and an MMF 12 that are connected and fixed to the two optical fiber connectors 20 and 21 respectively, and a connection portion 10 that is inserted between the SMF 11 and the MMF 12.
[0014]
A duplex optical connector 22 of a transmission optical fiber cord is detachably connected to the optical connector coupling receptacle 23 of the patch panel 24.
[0015]
FIG. 8 is an enlarged view of the inside (only on the transmission side) of the optical fiber connection portion at a substantially middle point of the patch cord. For the sake of simplicity, the SMF protective sheath, the MMF protective sheath, the ferrule, and the like are omitted.
[0016]
The conventional mode conditioner has a configuration in which two duplex optical connectors 20 and 21 are connected and fixed with an optical fiber cord such as SMF 11 or MMF 12, and a connecting portion 10 is provided in the middle of the optical fiber cord. The SMF 11 is used only for the optical fiber coupled to the transmission side of the optical transceiver 30, and the MMF 12 is used for the other optical fibers. On the transmission side (lower side in the figure) of the connection unit 10, the SMF 11 and the MMF 12 are fusion-bonded with the core center shifted. The light input to the SMF 11 from the optical transceiver 30 is incident on the MMF 12 while avoiding the central portion of the core, that is, the mode is conditioned only to the higher order mode. Since the light once shifted from the center hardly enters the low refractive index portion at the core center during propagation, the influence of DMD can be avoided.
[0017]
Note that this mode conditioner can be used for the MMF 12 having no abnormal refractive index as shown in FIG. In addition, since mode conditioning is not necessary on the receiving side, the MMFs 12 may be fused without shifting at the connection unit 10 or optical connectors may be provided at both ends of one MMF 12 like a normal optical jumper.
[0018]
[Problems to be solved by the invention]
By the way, the conventional technique is characterized in that the SMF 11 and the MMF 12 are fusion-bonded by shifting the center of the core, but a system using such a patch cord and the patch cord itself are expensive.
[0019]
(1) Patch cords Using the latest fully automatic fusion splicer, connecting only fiber strands (fusion) is not as difficult as before, but splicing work must still be performed carefully by skilled workers. There is. Further, this fusion splicing is a precision operation in which the fusion is performed by shifting the center unlike a normal fusion splicing, but it is not easy to manufacture stably so that this deviation is constant. In addition, since the inspection after the manufacturing cannot be performed by measuring only the passage loss, the manufacturing cost due to the inspection work is increased. Moreover, it is necessary to manually connect the coating and the reinforcing material (Kevlar etc.) after the fiber strands are fused, which is very troublesome.
[0020]
(2) When using an existing optical fiber cable using a patch cord, it is necessary to replace the normal patch cord with a dedicated patch cord, which costs the dedicated patch cord itself and the cost of replacement work. Furthermore, since this dedicated patch cord cannot be used for other purposes, it must be sufficiently managed so as not to be misused during construction.
[0021]
Accordingly, an object of the present invention is to provide a mode conditioner that solves the above problems and suppresses the influence of DMD when laser light is transmitted using a multimode optical fiber.
[0022]
[Means for Solving the Problems]
In order to achieve the above object, a mode conditioner of the present invention is a mode conditioner in which a duplex optical connector is connected and fixed to both ends of a patch cord having a single mode optical fiber and a multimode optical fiber. One duplex optical connector is detachably connected to the optical transceiver so that the single mode optical fiber is on the optical transmitter side of the optical transceiver and the multimode optical fiber is on the optical receiver side of the optical transceiver. together, two consecutive optical connector of the other, in two multimode connected fixed duplicate optical connector and to one end of the transmission optical fiber cord made of optical fiber detachably connected thereto mode conditioner, the other 2 The end face of the single-mode optical fiber of the continuous light connector is polished obliquely with respect to the optical axis together with the ferrule that holds it, When the other duplex optical connector and the transmission optical fiber cord side duplex optical connector are connected, a space is formed between the obliquely polished single mode optical fiber end surface and the transmission optical fiber cord side multimode optical fiber end surface. Is formed .
[0023]
In addition to the above configuration, the mode conditioner of the present invention is such that the end surface of the single-mode optical fiber of the other duplex optical connector is partly polished with respect to the optical axis together with the ferrule holding it, and the remaining part is polished vertically. It is desirable that
[0024]
The mode conditioner of the present invention is a mode conditioner comprising a single-mode optical fiber and a multi-mode optical fiber, an adapter having a duplex optical connector at one end and a receptacle at the other end. The optical connector is detachably connected to the optical transceiver so that the single mode optical fiber is on the optical transmitter side of the optical transceiver and the multimode optical fiber is on the optical receiver side of the optical transceiver, and the receptacle is In a mode conditioner that is detachably connected to a duplex optical connector that is connected and fixed to one end of a transmission optical fiber cord composed of two multi-mode optical fibers, the end surface of the single-mode optical fiber of the receptacle holds this Polished with the ferrule at an angle with respect to the optical axis, receptacle and optical fiber for transmission Upon connecting the over de side duplicate optical connector, in which a space is formed between the oblique polished single-mode optical fiber end face and the transmission optical fiber cord side multimode optical fiber end face.
[0025]
In addition to the above-described configuration, the mode conditioner of the present invention is such that the single-mode optical fiber end face of the receptacle is partly polished with respect to the optical axis together with the ferrule holding it, and the remaining part is polished vertically. Features.
[0026]
According to the present invention, when a single mode optical fiber whose other end is polished obliquely with a ferrule is connected to a multimode optical fiber subjected to normal polishing, laser light is incident from one end of the single mode optical fiber. The light emitted from the other end of the single-mode optical fiber spreads obliquely in the space while spreading, but almost no light enters the low-refractive index portion in the center of the multi-mode optical fiber, and the other core has sufficient light. Therefore, transmission characteristic deterioration due to band deterioration caused by DMD can be avoided. Therefore, it is possible to provide a mode conditioner that suppresses the influence of DMD when transmitting laser light using a multimode optical fiber.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0028]
FIG. 1 is a connection state diagram showing an embodiment of a mode conditioner of the present invention, and FIG. 2 is a partially enlarged view showing a connection state of an optical connector of the mode conditioner shown in FIG. Note that the protective sheaths of SMF and MMF are omitted for the sake of simplicity.
[0029]
One end of the MMF 12 (left end in the figure) and one end of the SMF 11 (left end in the figure) are connected and fixed to the duplex optical connector 20 shown in FIG. 1, respectively, and the other end of the MMF 12 (right end in the figure) and the SMF 11 The other end (right end in the figure) is connected and fixed to the duplex optical connector 21. While the end face of the MMF 12 of the duplex optical connector 21 is polished normally, that is, polished with the ferrule 33 in the longitudinal direction, the end face 26 on which the SMF 11 is connected to the MMF 32 of the transmission optical fiber cord is shown in FIG. As shown in FIG. 2, the ferrule 34 is polished obliquely.
[0030]
Rather than completely polishing the other end of the SMF 11, it is preferable that a part of the ferrule 34 is polished perpendicularly to the longitudinal direction and the remaining part is polished diagonally as shown in FIG. This is because when the duplex optical connector 21 is connected to the optical connector coupling receptacle 23, the ferrule 34 hits the ferrule 33 in the split sleeve in the optical connector coupling receptacle 23, and damages the split sleeve 27. This is because it is possible to prevent the ferrules 33 and 34 from being chipped or the optical axis from shifting.
[0031]
This mode conditioner is composed of a duplex optical connector 20, a duplex optical connector 21, an MMF 12, and an SMF 11 in which the end face connected to and fixed to the duplex optical connector 21 is polished obliquely together with the ferrule 34. The patch cord is formed.
[0032]
The duplex optical connector 20 of such a patch cord type mode conditioner is detachably connected to an optical transmitter having a laser light source of the LAN device 31, and the duplex optical connector 21 is a patch panel. It is detachably connected to 24 optical connector coupling receptacles 23. Further, the optical connector coupling receptacle 23 is detachably connected to the duplex optical connector 22 of the transmission optical fiber cord.
[0033]
Next, the operation of the present mode conditioner will be described with reference to FIG.
[0034]
FIG. 3 is a partially enlarged view of a connection portion between the SMF and the MMF shown in FIG.
[0035]
The light incident / exit portions of the end surfaces of the two ferrules 33 and 34 are not in contact with each other, and a space is formed. The light emitted from the oblique end face through the SMF 11 travels obliquely (upward in the drawing) while spreading and enters obliquely at a position shifted from the center of the core of the MMF 32. For this reason, light does not enter the low refractive index portion at the center of the MMF 32, or even if it enters, the amount is small, and transmission characteristic deterioration due to band deterioration due to DMD can be avoided. Therefore, it is possible to provide a mode conditioner that suppresses the influence of DMD when laser light is transmitted by MMF.
[0036]
For this reason, it is not necessary to connect a conventional optical fiber cord in the middle, and it can be produced by a process substantially similar to a normal patch cord, and the cost can be greatly reduced.
[0037]
FIG. 4 is a connection state diagram showing another embodiment of the mode conditioner of the present invention.
[0038]
The difference from the mode conditioner shown in FIG. 1 is that it is integrated with an “adapter” inserted between the optical transceiver 30 and the duplex optical connector 22 of the patch cord without using an optical fiber cord. (Mode conditioning adapter 25).
[0039]
FIG. 5 is an enlarged view of the ferrule part of the mode conditioner shown in FIG.
[0040]
The ferrule 35 inside the mode conditioning adapter 25 has both ends 36 and 37 polished, one end 36 is detachably connected to the optical transceiver 30, and the other end 37 is detachably connected to the duplex optical connector 20. It is like that. The ferrule 35 connected to the transmission side of the optical transceiver 30 has an SMF 38 inserted and fixed, and only the other end (light emitting surface) 37 is polished obliquely. A multimode fiber is inserted and fixed to the ferrule connected to the receiving side of the optical transceiver 30 (not shown). Based on the same principle as that of the patch cord type mode conditioner shown in FIG. 1, since the light offset to the SMF 11 is incident obliquely, the influence of DMD can be avoided.
[0041]
Since this adapter does not require an optical connector terminal processing operation of an optical fiber cord and is composed of only parts with good mass productivity, it can be manufactured at a much lower cost than a patch cord. In addition, since the patch cord that has been used conventionally can be used as it is, the change work can be greatly simplified when performing high-speed optical transmission with the existing optical fiber.
[0042]
The mode conditioner shown in FIGS. 1 and 4 is for connecting to an optical transceiver in which an optical transmitter and an optical receiver are integrated. Since the optical receiving side of the optical transceiver does not require the mode conditioning effect, it does not need to be integrated depending on the use situation. If only the transmitting side is made independent, the receiving side can be omitted depending on the form of the optical transceiver, and the cost can be reduced.
[0043]
As described above, according to the present invention, the end face of a single mode optical fiber connected to the multimode optical fiber is polished obliquely together with the ferrule, thereby suppressing the influence of DMD when laser light is transmitted through the multimode optical fiber. It is possible to provide a mode conditioner.
[0044]
In the present embodiment, the case where the optical connector is a dual optical connector has been described. However, the present invention is not limited to this, and a single optical connector or three or more optical connectors may be used.
[0045]
【The invention's effect】
In short, according to the present invention, the following excellent effects are exhibited.
[0046]
It is possible to provide a mode conditioner that suppresses the influence of DMD when transmitting laser light using a multimode optical fiber.
[Brief description of the drawings]
FIG. 1 is a connection state diagram showing an embodiment of a mode conditioner of the present invention.
FIG. 2 is a partially enlarged view showing a connection state of the optical connector of the mode conditioner shown in FIG. 1;
3 is a partial enlarged view of a connection portion between the SMF and the MMF shown in FIG.
FIG. 4 is a connection state diagram showing another embodiment of the mode conditioner of the present invention.
FIG. 5 is an enlarged view of a ferrule part of the mode conditioner shown in FIG. 4;
FIG. 6 is a diagram showing a refractive index distribution of a multimode optical fiber having a low refractive index portion at the core central portion.
FIG. 7 is a diagram showing a conventional example of a patch cord type mode conditioner.
FIG. 8 is an enlarged view of the inside of the optical fiber connection portion at a substantially middle point of the patch cord.
[Explanation of symbols]
11 SMF
20, 21 Double optical connector 32 MMF

Claims (4)

A mode conditioner in which a duplex optical connector is connected and fixed to both ends of a patch cord having a single mode optical fiber and a multimode optical fiber, and one of the duplex optical connectors is optically coupled to the single mode optical fiber. The multimode optical fiber is detachably connected to the optical transmitter / receiver so that the multimode optical fiber is on the optical receiver side of the optical transmitter / receiver. In a mode conditioner that is detachably connected to a duplex optical connector that is connected and fixed to one end of a transmission optical fiber cord comprising a multi- mode optical fiber, the end surface of the single mode optical fiber of the other duplex optical connector Are polished obliquely with respect to the optical axis together with the ferrule that holds the same, Upon connecting the use optical fiber cord side duplicate optical connector, characterized in that the space is formed between the oblique polished single-mode optical fiber end face and the transmission optical fiber cord side multimode optical fiber end face A mode conditioner. The single-mode optical fiber end face of the other duplex optical connector is partly polished with respect to the optical axis together with a ferrule holding the same, and the remaining part is polished vertically. The mode conditioner according to 1. A mode conditioner comprising a single-mode optical fiber and a multi-mode optical fiber, an adapter having a duplex optical connector at one end and a receptacle at the other end, wherein the duplex optical connector includes the single-mode optical fiber The optical transceiver is detachably connected to the optical transceiver such that the fiber is on the optical transmitter side of the optical transceiver and the multimode optical fiber is on the optical receiver side of the optical transceiver, and the receptacle has two receptacles. In a mode conditioner that is detachably connected to a duplex optical connector that is connected and fixed to one end of a transmission optical fiber cord made of a multimode optical fiber, the end surface of the single mode optical fiber of the receptacle together with a ferrule holding the same Polished at an angle with respect to the optical axis, the receptacle and the transmission optical fiber Upon connecting the over de side duplicate optical connector, and a space is formed between the oblique polished single-mode optical fiber end face and the transmission optical fiber cord side multimode optical fiber end face Mode conditioner. 4. The mode according to claim 3, wherein the end surface of the single-mode optical fiber of the receptacle is partly polished with respect to the optical axis together with the ferrule holding the same, and the remaining part is polished vertically. Conditioner.

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