JPH08265255A - Optical fiber access coupler - Google Patents

Abstract

PURPOSE: To easily realize low insertion loss and high optical isolation characteristics with simple constitution by providing two optical fiber welding optical multiplexers/demultiplexers for multiplexing and demultiplexing the optical, signals of respectively specified wavelengths and band pass optical filters corresponding to the wavelengths of the optical signals. CONSTITUTION: This coupler is provided with a single mode optical fiber welding optical multiplexer/demultiplexer 1 capable of multiplexing and demultiplexing the optical signals of the wavelength 1.2μm and the optical signals for which the wavelengths 1.31μm and 1.55μm are mixed, the single mode optical fiber welding optical multiplexer/demultiplexer 2 cascade connected to the welding optical multiplexer/demultiplexer 1 capable of multiplexing and demultiplexing the optical signals of the wavelength 1.31μm and the optical signals of the wavelength 1.55μm and the band pass optical, filters 3-5 provided on single mode optical fiber transmission lines corresponding to the respective wavelengths to be the input/output ports of the respective wavelengths 1.2,μm, 1.31μm and 1.55μm. By this optical fiber access coupler, the respective ports can realize the low insertion loss and the high optical isolation characteristics in a 3ch bidirectional communication system.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication service in which an access network is made into an optical fiber, and more particularly to a bidirectional 3-channel optical access coupler.

[0002]

2. Description of the Related Art The history of communication services starting from telephone is 10
It has been 0 years. In particular, the spread of optical fiber communication systems has been remarkable in recent years, and the use of optical fibers for access networks in subscriber systems is approaching practical use. A passive double star (hereinafter, abbreviated as PDS) system has been proposed as one of the narrow band optical subscriber systems for such optical fiber access networks. In this PDS system, a star coupler is placed in the vicinity of a subscriber, and a plurality of subscribers are multiplexed by the coupler.
The S system is composed of a 1.55 μm 1 channel (hereinafter abbreviated as ch) 1.31 μm 2 ch two-way communication system, that is, a two-wavelength 3 ch two-way communication system has been known and studied.

FIG. 2 is a schematic configuration diagram showing a configuration example of an optical access coupler section in such a system. In FIG. 2, 101 is a 1.31 μm / 1.55 μm single-mode optical fiber fusion-splicing demultiplexer, 102 is a 1.31 μm bandpass optical filter, and 103 is 1.55.
A μm band pass optical filter, 104 to 107 are optical connectors, 108 and 109 are non-reflective terminators, and 110 is a single mode optical fiber fusion optical branch coupler.

The operation of this conventional example is as follows. Figure 2
As shown in FIG.
A 5 μm optical signal is a single mode optical fiber fusion-splicing demultiplexer 101 and 1.5 for 1.31 μm / 1.55 μm.
Optical connector 1 passing through a 5 μm bandpass optical filter 103
It is emitted to 05. In this case, since the typical insertion loss of each of the optical fiber fusion splicing demultiplexer 101 and the bandpass optical filter 103 is 1 dB or less, the optical connector 104,
The insertion loss excluding the connection loss of 105 can be 2 dB or less.

Also, the optical isolation in the optical connector 105 is 1.55 μm bandpass optical filter 10.
3, it is possible to easily realize a characteristic of 50 dB or more. An optical signal having a wavelength of 1.31 μm enters from the optical connector 104 and is output to the optical connector 106. Also,
The optical signal having the wavelength of 1.31 μm enters from the optical connector 107, and passes through the optical branching / coupling device 110.
It is emitted from 6. In this case, the 1.31 μm optical signal has a large insertion loss due to the optical branching / coupling device 110 which is a 3 dB coupler.

[0006]

In the above-mentioned conventional optical access coupler, the optical fiber fusion splicing coupler 110 is used for performing 2-channel bidirectional communication of 1.31 μm. Therefore, the insertion loss as an optical access coupler is
The branch loss alone is 3 dB or more. For this reason, the total loss is generally required to be 5 dB or less,
Considering the wavelength variation of the light source and the temperature dependence of the coupler characteristics, there is a problem that the above characteristics cannot be realized at the input / output port of 1.31 μm. Furthermore, optical isolation characteristics of optical access couplers are required to be 40 dB or more in Japan and 50 d in Europe and America.
Although B or more is required, the conventional optical access coupler has a problem in that only 1.3 dB of optical isolation can be obtained with a 1.31 μm sending port.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide an optical access coupler which can easily realize low insertion loss and high optical isolation characteristics with a simple structure.

[0008]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides:
A single mode optical fiber fusion optical multiplexer / demultiplexer capable of multiplexing and demultiplexing an optical signal of 2 μm and an optical signal in which wavelengths 1.31 μm and 1.55 μm are mixed, and a cascade connection to the fusion optical multiplexer / demultiplexer Connected, 1.31 μm wavelength optical signal and 1.55 wavelength
a single mode optical fiber fusion optical multiplexer / demultiplexer capable of multiplexing and demultiplexing an optical signal of μm, and the aforementioned 1.2 μm and 1.31 μm
Provided is an optical fiber access coupler provided with a bandpass optical filter provided corresponding to each wavelength in a single mode optical fiber transmission line serving as an input / output port for each wavelength of m and 1.55 μm.

Further, in the optical fiber access coupler according to the present invention, a bandpass optical filter having a wavelength band for allowing the wavelength of each optical signal to pass is provided in the optical fiber transmission line in which each optical signal is separated. Furthermore, the optical fiber access coupler according to the present invention is provided with a convex spherical PC polished optical connector or an oblique polished optical connector at the end of the optical fiber for inputting and outputting the optical signal.

[0010]

In the present invention, the optical access coupler uses signals of three wavelengths of 1.2 μm, 1.31 μm and 1.55 μm. As a result, the system can be configured only with the optical fiber fusion splicing demultiplexer and the bandpass optical filter, and low insertion loss and high optical isolation characteristics can be easily realized.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of an optical access coupler according to the present invention. In the figure, 1 is a 1.2 μm / (1.31 μm + 1.55 μm) single-mode optical fiber fusion-splicing demultiplexer, and 2 is 1.31 μm.
/1.55 μm single mode optical fiber fusion splicing demultiplexer, 3 for 1.2 μm bandpass optical filter, 4 for 1.
31 μm bandpass optical filter, 5 is a 1.55 μm bandpass optical filter, 6, 6 ′, 6 ″, 6 ′ ″ are optical connectors, and 7 ′ and 7 ″ are non-reflection terminators.

The operation of this embodiment will be described below.
The explanation of the operation below is for the optical connector 6 with 1.2 μm and 1.3 μm.
The signal of 1 μm is input and 1.55 from the optical connector 6 '.
This is performed for the case where a μm signal is output. The optical signal of 1.2 μm incident on the optical connector 6 is 1.2 μm /
(1.31 μm + 1.55 μm) After passing through the single mode optical fiber fusion-splicing demultiplexer 1, after passing through the 1.2 μm bandpass optical filter 3, it is emitted from the optical connector 6 ′.

Since the typical insertion loss of each of the optical fiber fusion-splicing demultiplexer 1 and the band-pass optical filter 3 is 1 dB or less, the connection loss between the optical connectors 6 and 6'excluding the connection loss of the optical connectors 6 and 6 '. Insertion loss is less than 2 dB. In addition, the optical isolation in the optical connector 6'can easily be 50 dB or more by using the bandpass optical filter.

Next, let us consider the insertion loss and the optical isolation in the same way for the 1.31 μm signal that is incident from the optical connector 6 and is emitted to the optical connector 6 ″. This 1.3
Two single-mode optical fiber fusion-splicing demultiplexers 1 and 2 and one 1.31 μm band-pass optical filter 4 are arranged in the propagation path of the signal of 1 μm. The insertion loss between 6 "is less than 3dB, and the optical isolation at the optical connector 6" is 50dB.
It is possible to realize a characteristic of dB or more. Finally, 1.5 is emitted from the optical connector 6 ′ ″ to the optical connector 6 ′.
Similarly, for a signal of 5 μm, it is possible to easily realize the characteristics of insertion loss of 3 dB or less and optical isolation of 50 dB or more.

As described above, according to the optical access coupler of the present invention, it is possible to realize low insertion loss and high optical isolation characteristics at each port in the 3ch bidirectional communication system. Optical connector 6, 6 ', 6'',
For 6 ″, the use of a convex spherical PC polished optical connector can achieve a return loss of −40 dB or less, and the use of an 8 ° oblique polished optical connector allows a return loss of −60 dB or less. Therefore, the optical access coupler as a whole can realize an optical isolation characteristic of 40 dB or more.

[0016]

As described above, according to the present invention,
Optical fiber fusion optical multiplexer / demultiplexer for multiplexing / demultiplexing optical signals with wavelengths 1.2 μm, 1.31 μm, and 1.55 μm, and light for multiplexing / demultiplexing optical signals with wavelengths 1.31 μm and 1.55 μm By providing the fiber fusion optical multiplexer / demultiplexer and the bandpass optical filter provided corresponding to the wavelengths of these optical signals, it is possible to easily realize low insertion loss and high optical isolation characteristics with a simple configuration. is there.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an optical access coupler according to the present invention.

FIG. 2 is a configuration diagram showing a conventional example of an optical access coupler.

[Explanation of symbols]

1 1.2 μm / (1.31 μm + 1.55 μm) single mode optical fiber fusion-splicing demultiplexer, 2 1.31
Single-mode optical fiber fusion-splicing demultiplexer for μm / 1.55 μm, 3 1.2 μm bandpass optical filter, 4
1.31μm bandpass optical filter, 5 1.55μ
m bandpass optical filter, 6,6 ', 6 ", 6'"
Optical connector, 7 ', 7''non-reflective terminator, 101
1.31 μm / 1.55 μm single mode optical fiber fusion splicing demultiplexer, 102 1.31 μm bandpass optical filter, 103 1.55 μm bandpass optical filter, 104 to 107 optical connector, 108, 109 non-reflection termination , 110 single mode optical fiber fusion splicing coupler

Claims (2)

[Claims] 1. An optical signal having a wavelength of 1.2 μm and a wavelength of 1.3 μm.
A single mode optical fiber fusion optical multiplexer / demultiplexer capable of multiplexing and demultiplexing an optical signal mixed with 1 μm and 1.55 μm, and a cascade connection of the fusion optical multiplexer / demultiplexer with a wavelength of 1.31 μm
Single-mode optical fiber fusion optical multiplexer / demultiplexer capable of multiplexing and demultiplexing the optical signal of 1 .5 and the optical signal of wavelength 1.55 .mu.m, and input / output of each wavelength of 1.2 .mu.m, 1.31 .mu.m and 1.55 .mu.m An optical fiber access coupler comprising: a single-mode optical fiber transmission line serving as a port; and a bandpass optical filter having a wavelength band that allows the wavelength of each optical signal to pass therethrough. 2. The optical fiber access coupler according to claim 1, wherein a convex spherical PC polished optical connector or an oblique polished optical connector is provided at an end portion of the optical signal input / output optical fiber.