JP2610211B2 - Excessive light blocking device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical circuit component mounted on an optical transmission line such as an optical communication device and the like. The present invention relates to a light blocking device.

[0002]

2. Description of the Related Art With the advancement of optical circuit technology, the intensity of laser light sources used for optical communication and the like is gradually increasing. Is propagated, and optical components such as an optical isolator and a light receiving element may be destroyed. Therefore, there is a need to protect the optical circuit components from such excessive light. However, there has been no suitable light blocking device that meets this purpose.

[0003]

There is an optical attenuator as an apparatus for adjusting the intensity of light propagating on an optical circuit. Inserting this optical attenuator into the optical circuit has the effect of preventing excessive light from propagating to the subsequent stage to some extent, but it also attenuates light at normal levels in normal conditions. Therefore, the circuit breaker is essentially different from a circuit breaker that operates only for an excessive input, such as an overcurrent circuit breaker or an overvoltage circuit breaker in an electric circuit.

The present invention has been made in view of the above-mentioned conventional problems, and has as its object to operate when the intensity of light propagating on an optical transmission line comprising an optical fiber exceeds a specified level. It is an object of the present invention to provide an excessive light blocking device that blocks light and prevents light from attenuating in a normal state as much as possible.

[0005]

According to the present invention, there is provided an excess light blocking device for extracting a part of light propagating through a main transmission line using an optical fiber, such as an optical communication device, as monitor light at a constant intensity ratio. And an optical delay means comprising an optical fiber for delaying the propagation of light on the main transmission path via the optical branching means; an optical switch for blocking the propagation of light on the main transmission path via the optical delay means; Light detecting means for generating an electric signal corresponding to the intensity of the monitor light taken out by the light branching means, comparing means for discriminating the output of the light detecting means, and the output of the light detecting means being set by the comparing means Driving means for turning off the optical switch when it is detected that the level has been exceeded.

[0006]

Strictly speaking, the insertion of the optical branching means and the optical delay means into the main transmission path gives a slight loss to the main transmission path, but this transmission loss is sufficiently small to be negligible. can do. The intensity of the light propagating through the main transmission path is constantly monitored by the light detecting means and the comparing means, and when light having an excessive intensity exceeding a set level is detected, the drive circuit shuts off the optical switch. State. Although a certain delay time occurs from the time when the excessive light propagates to the time when the optical switch is cut off, the optical delay means inserted between the optical branch interruption and the optical switch absorbs the response delay.

[0007]

FIG. 1 shows a schematic configuration of an excessive light blocking device according to an embodiment of the present invention. The optical splitter 2, the delay optical fiber 3, and the optical switch 4, which constitute the excessive light blocking device of the present invention, are provided between the input optical fiber 1 and the output optical fiber 5 constituting the main transmission line. They are inserted in order.

The optical splitter 2 is for branching out monitor light for measuring the intensity of light propagating through the main transmission line from the main transmission line and extracting the monitor light, regardless of the polarization state of the input light. The light of the ratio is configured to be branched and output as monitor light. The intensity ratio of the branched light is preferably as small as possible, for example, preferably about 0.5%. The optical branching device 2 of the illustrated embodiment has a birefringent plate 23 and a tilt with respect to the main optical axis between the fiber collimator 21 of the input optical fiber 1 and the fiber collimator 22 of the delay optical fiber 3. And a glass plate 24 with a dielectric thin film. The light axis of the birefringent plate is inclined by 45 ° with respect to the plane of incidence of light on the glass plate with the dielectric thin film. The present invention is not limited to such a polarization beam splitter type optical splitter 2, and a well-known optical fiber coupler can be used as an optical splitter having the same function as described above.

99% of the light propagating through the input side optical fiber 1
The above is transmitted to the delay optical fiber 3 via the optical splitter 2. The delay optical fiber 3 is inserted to increase the propagation time as described below, and its length is determined according to the required delay time.

The optical switch 4 normally transmits the input light to the output side optical fiber 5 without any loss, enters a cutoff mode in response to a signal from a drive circuit described later, and transmits the input light to the output side optical fiber 5. Completely shut off. The optical switch 4 of this embodiment includes a fiber collimator 41 on the delay optical fiber 3 side and a fiber collimator 4 on the output side optical fiber 5.
2, the birefringent plate 43 and the Faraday effect element plate 4
4, a half-wave plate 47, and a birefringent plate 45. As is well known, the Faraday effect element plate 44 is provided.
The optical switch 4 is turned on / off by a signal applied to a coil of an exciter 46 attached to the optical switch 4. In addition, optical switches of various types and configurations can be used.
That is, for example, there are a device using an electro-optical device such as PLZT instead of the Faraday effect device plate and the half-wave plate, a device using an actuator to mechanically displace a shutter or a reflector. All of these can be applied to the present invention.

The monitor light split by the optical splitter 2 is received by a photodetector 6 from which an optical fiber 1
And outputs an electric signal corresponding to the intensity of the input light.
As the photodetector 6, basically any device may be used as long as the required sensitivity and accuracy for the light of the used wavelength can be obtained. The wavelength band of laser light currently generally used for optical communication is 1.31 or 1.55 micrometers. In this case, a semiconductor sensor such as a photodiode or a photoconductive element is suitable.

The output signal of the photodetector 6 is pre-processed by a preamplifier 7 and input to a comparator 8 serving as a comparing means, where it is compared with an appropriately set reference level signal Vs. The drive circuit 9 receives the level discrimination output of the comparator 8 and drives the optical switch 4. That is, when the detection level by the photodetector 6 is equal to or lower than the reference level, the optical switch 4 is kept on, and the input light propagates to the output side optical fiber 5. on the other hand,
When the detection level of the input light exceeds the reference level, the output of the comparator 8 is inverted. At this time, the optical switch 4 is turned off, and the light propagation to the output side optical fiber 5 is cut off.

Although there is some response delay from when the intensity of the input light becomes excessive to when the optical switch 4 is turned off, the delay time (the length of the optical fiber) of the delay optical fiber 3 is determined by the response time. Set slightly longer than the time. Then, excessive input light will not be transmitted to the output side optical fiber 5. If the response time is 0.5 to 20 microseconds, the length of the delay optical fiber 3 is 100 to 400 microseconds.
0 meters.

[0014]

As described above in detail, according to the excessive light blocking device of the present invention, if the light intensity propagating through the main transmission line composed of an optical fiber falls within the normal level range, the light transmission with respect to the main transmission line is prevented. With almost no transmission loss
When the light intensity propagating through the main transmission line increases for some reason and exceeds the specified level, the optical switch is turned off in response to the excessive light, and the excessive light is reliably prevented from being transmitted to the subsequent optical circuit. Can be.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an excessive light blocking device according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 1 input side optical fiber (main transmission line) 2 optical branching device (optical branching means) 3 delay optical fiber (optical delaying means) 4 optical switch 5 output side optical fiber 6 photodetector (photodetecting means) 8 comparator (comparison) Means) 9 drive circuit (drive means)

Claims (1)

(57) [Claims] The method according to claim 1 Some of the light propagating in the main transmission path using an optical fiber and an optical branching means for taking out only as a monitor light constant intensity ratio, the light branching means the propagation of light of the main transmission line passing through delay Optical delay means comprising an optical fiber for causing the light to travel, an optical switch for blocking propagation of light on the main transmission path via the optical delay means, and an electric signal corresponding to the intensity of the monitor light extracted by the optical branching means. And a comparing means for level discriminating the output of the light detecting means, and shutting off the optical switch when the comparing means detects that the output of the light detecting means exceeds a set level. An excessive light blocking device, comprising: driving means for setting a state.