JP2851066B2 - Interference light blocking device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interference light blocking device used for blocking interference light input to an optical star coupler constituting a 1: n bidirectional optical communication system.

[Conventional technology]

FIG. 5 is a block diagram showing a configuration of a conventional one-to-one bidirectional optical communication system.

In the figure, a terminal device 91 and a station device 92 perform two-way communication via an optical fiber. Here, a system configuration related to communication from the terminal device 91 to the station device 92 will be described.

In the terminal device 91, a light source 94 that performs intensity modulation according to transmission signal information output from the processing circuit 93 transmits signal light having a predetermined wavelength. In the station device 92, the signal light is received by the detection circuit 96, and the received signal information is input to the processing circuit 97 to perform reception processing. In the station device 92, the output of the detection circuit 96 is adjusted via the automatic gain adjustment circuit (AGC circuit) 98 to adjust the reception signal level.

In the station device 92, a pseudo line (BON) 95 is inserted at the input stage of the detection circuit 96 in addition to the automatic gain adjustment circuit (AGC circuit) 98 as a measure against excessive light.

FIG. 6 is a block diagram showing a configuration of a 1: n bidirectional optical communication system.

In the figure, a plurality of terminal devices 67 _1, 67 _2, ..., between 67 _n and the station device 72, the optical fiber 68 _0, 68 _1, 68 _2, ..., constituted by 68 _n and the optical star coupler 70 An optical communication network is set up, and bidirectional communication is performed by a wavelength division multiplexing method of each signal light of wavelength λ _{1 on the} downstream line and wavelength λ _{2 on} the upstream line.

The station device 72 includes a processing circuit 79 for performing signal transmission / reception processing,
A light source 80 that outputs a signal light of wavelength λ ₁ that is intensity-modulated according to the transmission signal information input from the processing circuit 79, and a detection circuit that receives the signal light of wavelength λ ₂ and outputs the received signal information to the processing circuit 79. 78, a wavelength multiplexing circuit 77 for wavelength multiplexing / demultiplexing the signal lights of wavelengths λ ₁ and λ ₂ .

Each terminal device 67 is a processing circuit that performs signal transmission / reception processing.
73, a light source 74 for outputting a signal light intensity-modulated wavelength lambda ₂ in response to the transmission signal information inputted from the processing circuit 73, the wavelength lambda
_{It comprises} a detection circuit 76 for receiving _one signal light and outputting received signal information to the processing circuit 73, and a wavelength multiplexing circuit 75 for wavelength multiplexing / demultiplexing each signal light of wavelength λ ₁ λ ₂ .

The optical star coupler 70 is a terminal device 67 for the uplink.
A function of binding one optical signal having a wavelength lambda ₂ from, for downlink has a function for branching the signal light of the wavelength lambda ₁ from station device 72 into a plurality n.

The identification of the signal light corresponding to each terminal device is performed in the station device 72 and the terminal device 67 by a time division control method of detecting a position on the time axis allocated to each terminal device.

[Problems to be solved by the invention]

By the way, in the above-described one-to-n bidirectional optical communication system, since the transmission path is shared by the time-division control method, if the terminal device always emits light due to a failure, it becomes continuous light. The signal light transmitted from the normal terminal device is masked, and communication with the station device is interrupted.

In such a case, the station apparatus receives signal lights from a plurality of terminal apparatuses as signal lights combined into one using an optical star coupler, as in a one-to-one bidirectional optical communication system. In the method of installing an automatic gain adjustment circuit or a pseudo line inside the station device, it was not possible to remove only the interference light, and it was not possible to secure communication between a plurality of terminal devices and the station device.

Similarly, there is no countermeasure when a device that generates high-power interference light is connected to a certain terminal device.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an interference light blocking device that protects communication between a plurality of terminal devices and a station device coupled by an optical star coupler from interference light. And

[Means for solving the problem]

 FIG. 1 is a block diagram showing the principle of the present invention.

In the figure, an optical branching means which is connected to an n-branched input stage of an optical star coupler for branching and coupling signal light into one-to-n ratios, and for branching a part of incident light of the optical star coupler, and an intensity of the branched incident light Detect peak value or average value for
When at least one of the peak value or the average value is a value indicating abnormality with respect to the predetermined value, incident light abnormality detection means for outputting a predetermined control signal, and according to the control signal, the incident light of the optical star coupler. And an optical switch means for blocking.

(Operation)

The interfering light includes continuous light due to a failure of the terminal device, interfering light having a high average light intensity by a device that generates the interfering light, or interfering light having a small time width but high light intensity.

The present invention is a light branching means and incident light abnormality detection means,
The intensity of the signal light incident on the optical star coupler is detected as its peak value or average value, and when at least one of the values is abnormal, the optical switch means uses the signal light as interference light. Cut off at the input stage of the optical star coupler. That is, since the interfering light is cut off at the input stage of the optical star coupler, it is possible to avoid the influence on the bidirectional communication system using the 1: n optical star coupler.

〔Example〕

FIG. 2 is a block diagram showing the configuration of the embodiment of the present invention.

In the figure, the interference light blocking device is arranged at a position where the interference light emitted from the terminal device is blocked at the input stage of the optical star coupler. That is, the output port 10 ₁ is connected to the optical fiber of the terminal device, the optical fiber of the optical star coupler side is connected to the output port 10 _2.

Signal light incident on the output port 10 _1, the optical switch 1
It is emitted to the output port 10 ₂ through the 1 and the optical branching device 20.

The optical switch 11, in this embodiment heat and Mahatsuenda interferometer constituted by two directions raw coupler 13 and 15 are connected by optical waveguides 16 _1, 16 _2, the optical waveguide 16 ₁ while the heater 17 Is realized by: Normally, the optical switch 11 emits signal light incident on one port of the directional coupler 13 from one port of the directional coupler 15, but the phase of the light changes by heating the heater 17. However, the thermo-optical switch is not emitted to one port of the directional coupler 15.

The optical branching unit 20 is composed of optical branching elements 21 and 22 of a waveguide type directional coupler that branches light output from the optical switch 11 into two. One output of the optical branching elements 21 and 22 is sent to the output terminal 10 ₂ as the signal light to be transmitted, the other is sent to the photoelectric conversion unit 30 to detect the interference light.

The light branching ratio in the light branching elements 21 and 22 is, for example, 100: 1.
Since signal light having a light intensity of 1/100 is input to the photoelectric conversion unit 30, normal signal transmission is not affected.

The photoelectric conversion unit 30 includes a photoelectric conversion element 31 connected to the optical branching element 21 and a photoelectric conversion element 33 connected to the optical branching element 22, and outputs signal light transmitted from the optical branching elements 21 and 22. The signal is converted into an electric signal and output to the control device 40 for detecting the presence or absence of the interfering light.

The photoelectric conversion element 31 is formed of, for example, a silicon photodiode, and has sensitivity in a short wavelength range of about 0.5 μm to 1.0 μm. The photoelectric conversion element 33 is made of, for example, a germanium photodiode and has sensitivity in a long wavelength region of about 0.7 μm to 1.6 μm.

That is, the light splitting elements 21 and 22 and the photoelectric conversion elements 31 and 33
This is a configuration for enabling photoelectric conversion in the entire wavelength range in which the optical fiber can transmit, converting all the incident signal light into electric signals, and outputting the electric signals to the control device 40.

The control device 40 includes a peak value detection system and an average value detection system corresponding to each of the photoelectric conversion elements 31 and 33, and has a function of heating the heater 17 of the optical switch 11 according to the detection of the interfering light. I have.

The peak value detection system detects peak values of the output signal levels of the photoelectric conversion elements 31 and 33 with the peak value detection circuits 41 and 43, compares both peak values with the comparator 45, and compares the larger peak value with the peak reference value. The comparator 47 compares a predetermined peak reference value output from the value output circuit 49 with a comparator 47, and outputs a predetermined control signal when the detected peak value is larger than the peak reference value.

The peak reference value is a reference value for determining whether or not the incident signal light is disturbing light, and is set to a higher level than the signal level during normal communication.

In the average value detection system, the average value detection circuits 51 and 53 detect the average value of the output signal levels of the photoelectric conversion elements 31 and 33,
The two average values are compared by a comparator 55, and the larger average value is compared by a comparator 57 with a predetermined average reference value output by an average reference output circuit 59, and the detected average value is compared with the average reference value. If it is larger, a predetermined control signal is output.

The average reference value is a reference value for determining whether or not the incident signal light is disturbing light, and is set to be higher than the average value during normal communication. That is, since the normal signal light is pulse-like and the signal light at the time of failure is continuous light, the difference in the average value occurs even if the peak values are the same.

The control signal outputs of the comparators 47 and 57, which are the results of the detection of the interference light based on the peak value and the detection of the interference light based on the average value, are input to the switch driving power supply 61 via the OR circuit 60.

The switch drive power supply 61 heats the heater 17 of the optical switch 11 according to each control signal. That is, the heater 17 of the optical switch 11 is heated according to the detection of the interfering light, so that the interfering light can be blocked at the input stage of the optical star coupler.

In addition, an optical branching element, a photoelectric conversion element, a peak value detection system,
The average value detection system has a configuration corresponding to each of the short wavelength region and the long wavelength region. However, if the structure is not disturbed by the interference light of the long wavelength (short wavelength) region, the configuration for the long wavelength (short wavelength) region is used. Can be omitted.

FIG. 3 is a block diagram showing an installation position of the interference light blocking device of the present invention in a 1: n bidirectional optical communication system.

In the figure, in a 1: n bidirectional optical communication system configured using a 1: n optical star coupler 70 between a station device 72 and a plurality of n terminal devices 67 _{1 to} 67 _n , each terminal device Corresponding interfering light blocking devices 69 _{1 to} 69 _n are installed at the input stages of the optical star coupler 70 on each terminal device side.

In the interfering light blocking device shown in FIG. 2, an optical switch, an optical branching unit, a photoelectric conversion unit, and a control device are installed for each input port, but an optical switch and an optical branching unit are installed for each input port. However, the photoelectric conversion unit and the control device can be shared. However, in this case, since the signal light transmitted from a plurality of terminal devices is detected by one control device, it is determined which signal light transmitted from any of the terminal devices is determined to be the interference light, and It is necessary to provide a control unit for opening the optical switch to be activated.

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

In the figure, an optical switch 81, an optical branching unit 84, a photoelectric conversion element 31, and a control device 90 are connected in the same manner as in the above-described embodiment.

However, the optical switch 81 is provided with a light shielding plate 82 for blocking incident light.
The optical switch according to the above-described embodiment is configured by a light-shielding plate driving device 83, and is a so-called mechanical switch in which the light-shielding plate 82 is inserted into the optical fiber according to the detection of the interfering light and the signal light is blocked. And different.

Further, the light branching unit 84 is configured by a branching mirror 84,
The difference is that the incident signal light is transmitted to the optical star coupler side and a part is reflected and output to the photoelectric conversion unit 31.

Note that the control device 90 includes the peak value detection circuit 40 for the short wavelength region, the peak reference value output circuit 49, the comparator 47, the average value detection circuit 51, and the average reference value output circuit 59 of the above-described embodiment.
, A comparator 57, an OR circuit 60, and a switch driving power supply 61.
And are similarly connected.

〔The invention's effect〕

As described above, according to the present invention, since the interfering light can be blocked on the terminal device side of the optical star coupler, communication between the other terminal devices and the station device is protected, and a highly reliable optical communication system is provided. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the principle of the present invention. FIG. 2 is a block diagram showing the configuration of the embodiment. FIG. 3 is a block diagram showing an installation position of the interference light blocking device of the present invention in a 1: n bidirectional optical communication system. FIG. 4 is a block diagram showing the configuration of another embodiment. FIG. 5 is a block diagram showing a configuration of a one-to-one bidirectional optical communication system. FIG. 6 is a block diagram showing a configuration of a 1: n bidirectional optical communication system. 10 I / O ports, 11, 81 Optical switches, 13, 15
... directional coupler, 16 ... optical waveguide, 17 ... heater, 20,
84 ... light branching unit, 21, 22 ... light branching element, 30 ... photoelectric conversion unit, 31, 33 ... photoelectric conversion element, 40, 90 ... control device,
41, 43 ... peak value detection circuit, 45, 47, 55, 57 ... comparator, 49 ... peak reference value output circuit, 51, 53 ... average value detection circuit, 59 ... ... average reference value output circuit, 60 ... OR circuit, 61 ... Switch drive power supply, 67 ... Terminal device, 68 ...
Optical fiber, 69: Interference light blocking device, 70: Optical star coupler, 72: Station device, 73, 79, 93, 97 Processing circuit, 7
4, 80, 94 ... light source, 75, 77 ... wavelength multiplexing circuit, 76, 7
8, 96 detection circuit, 82 light-shielding plate, 83 light-shielding plate driving device, 85 branch mirror, 95 pseudo-circuit (BON), 96
... Automatic gain adjustment circuit (AGC circuit).

Claims (1)

(57) [Claims] 1. An optical star coupler, which is connected to an n-branched input stage of an optical star coupler for branching and coupling signal light into one-to-n combinations, and branching a part of incident light of the optical star coupler; An incident light abnormality detection unit that detects a peak value or an average value with respect to light intensity, and outputs a predetermined control signal when at least one of the peak value or the average value is a value indicating abnormality with respect to a predetermined value. An optical switch means for interrupting the incident light of the optical star coupler in response to the control signal.