JPH05284114A - Optical repeater monitoring device - Google Patents

Abstract

PURPOSE:To perform optical branching accurately by a multi-wavelength coupler, and to add a monitoring function without degrading ability as an optical repeater by setting the wavelength of optical signals transmitted at the time of fault occurrence to the intermediate wavelength between the wavelengths of signal light and excitation light. CONSTITUTION:The wavelengths of excitation light sources 1 and 2 are defined as 1.48mum, the wavelength of the signal light is defined as 1.55mum, a semiconductor 21 is used for information transmitting at the time of failure occurrence, and its wavelength is defined as 1.53mum. At multi-wavelength couplers 3 and 4, approximately 20% of the output light of a semiconductor laser 21 is combined with an output fiber 23. Also at an erbium dope optical fiber amplifier 5, a gain peak is provided at the wavelengths of 1.530-1.536mum and 1.55-1.56mum, so that high gains can be expected for the light of the wavelength of 1.53mum at an optical amplifier, and when the information of fault is transmitted downstream with this wavelength, it can be transmitted while being amplified at respective optical repeaters.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical repeater using an optical amplifier, and relates to an optical repeater monitoring apparatus for transmitting information to the downstream when a failure occurs.

[0002]

2. Description of the Related Art An optical amplifier using an optical fiber containing a rare earth element such as erbium has a high gain and a large saturation output, and thus can be used for an optical repeater. When such an optical amplifier is used as an optical repeater, an important technical issue is how to monitor the optical repeater. Here, consider a system in which a plurality of optical repeaters are connected on an optical fiber.

As a minimum required monitoring function, it is necessary to have a function of notifying a downstream device that a failure has occurred when a failure occurs in the optical repeater. To realize such a function, a configuration as shown in FIG. 3 can be considered. In this figure, reference numerals 1 and 2 denote pumping light sources, and pumping light is input to an erbium-doped optical fiber 5 by wavelength multiplexing couplers 3 and 4. Reference numerals 6 and 7 denote optical isolators, which are inserted to suppress oscillation. The function of the optical amplifier is realized by the above configuration,
The LD 8 for transmission and the optical coupler 9 are required for communication of information when a failure occurs, and the optical coupler 10 and the photodetector 11 are required for receiving an upstream failure. That is, when a failure occurs in the optical repeater of the own station, the LD 8 outputs an optical signal to that effect to the optical repeater of another station connected downstream via the optical coupler 9. Further, when an optical signal indicating the occurrence of a failure is transmitted from the optical repeater of another station connected upstream, the optical signal is received by the photodetector 11 via the optical coupler 10.

By the way, in such a configuration, the optical output of the optical repeater is reduced by the optical coupler 9 even under normal conditions, and the signal light is reduced by the optical coupler 10 on the input side. Therefore, the gain and saturation output characteristics of the optical amplifier are apparently deteriorated. In order to solve such a problem, an optical switch may be used instead of the optical coupler 9. FIG. 4 is a diagram showing a configuration of an optical repeater provided with the optical switch 12. Here, normally, the optical switch 12 is connected to the optical isolator 7 and the signal light is directly transmitted downstream. When a failure occurs, the optical switch 12 is connected to the LD 8 and an optical signal to that effect is transmitted downstream. However, the optical switch is more expensive than the optical coupler, and the insertion loss of the signal accompanying the switching is large, so that it is not an effective solution.

[0005]

As described above, considering the addition of the monitoring function to the optical amplifier, the gain and saturation output characteristics are deteriorated and the performance of the optical repeater is deteriorated. An object of the present invention is to add a monitoring function without deteriorating the ability as an optical repeater.

[0006]

According to the present invention, a rare earth element-doped fiber for amplifying signal light from the upstream side by injecting pumping light and outputting the amplified signal light to the downstream side, and one input end downstream of the rare earth element fiber, and 2 inputs 2 with 1 output connected
Output first wavelength multiplexing coupler and two inputs 2 having one input end and one output end connected upstream of the rare earth element fiber
An output second wavelength multiplexing coupler; a pumping light source connected to the other input end of the first wavelength multiplexing coupler and the other input end of the second wavelength multiplexing coupler to output the pumping light; An optical transmitter connected to the other output end of the first wavelength multiplexing coupler and outputting a wavelength light between the pumping light wavelength and the signal light wavelength, and connected to the other output end of the second wavelength multiplexing coupler An optical repeater having an optical receiver for receiving the wavelength light from the upstream side, wherein the optical transmitter transmits the wavelength light through the wavelength multiplex coupler when a failure occurs in the optical repeater. The present invention relates to an optical repeater monitoring device characterized by transmitting to a downstream side.

[0007]

In the present invention, the wavelength of the optical signal to be transmitted when a failure occurs is set between the wavelength of the signal light and the wavelength of the pump light, so that the wavelength division multiplexer can accurately perform optical branching. That is, since the wavelength division multiplexer couples / branches the wavelengths of the signal light and the pumping light, there is an optical coupling state which is neither 0 nor 1 in the intermediate region between these two wavelengths. Therefore, it is possible to send this optical signal by connecting an optical transmitter that sends a signal at this intermediate wavelength to a wavelength multiplexing coupler installed downstream (rear), and wavelength multiplexing installed upstream (forward). If an optical receiver is connected to the coupler, the optical signal of this wavelength transmitted from the upstream can be received.

In an amplifier using an optical fiber doped with erbium as a rare earth element, the wavelength of pumping light is 1.4.
It is possible to use 8 μm and use a wavelength of 1.55 μm as the signal light. In this case, if the wavelength of 1.53 μm is used for the information transmission at the time of failure, the optical coupling of the wavelength multiplexing coupler will be 2
About 0% can be expected, and light with a wavelength of 1.53 μm is another gain peak of the optical amplifier, which is convenient.

[0009]

EXAMPLES Examples of the present invention will be described below.

FIG. 1 shows an embodiment of an optical repeater monitoring device according to the present invention. The same parts as those in FIG. 3 are designated by the same reference numerals. Reference numerals 1 and 2 denote excitation light sources, which are guided to the erbium-doped optical fiber 5 by the wavelength multiplexing couplers 3 and 4. Further, 6 and 7 are optical isolators for suppressing oscillation.
The above 1 to 7 constitute the optical amplifier.

Here, the wavelengths of the light sources 1 and 2 are 1.48 μm.
m, the wavelength of the signal light is 1.55 μm, the semiconductor laser 21 is used for transmitting information when a failure occurs, and its wavelength is 1.53 μm. If the WDM couplers 3 and 4 are fused optical fibers, two of the output lights of the semiconductor laser 21 will be used.
About 0% can be coupled to the output fiber 23. Further, in the erbium-doped optical fiber amplifier, the wavelength is 1.530-
It has one gain peak at 1.536 μm and wavelength 1.
It has another gain peak at 55 to 1.56 μm. Therefore, light having a wavelength of 1.53 μm can be expected to have a high gain in the optical amplifier, and if the information of the fault is transmitted downstream at this wavelength, it can be transmitted while being amplified by each optical repeater.

The fault information from the upstream can be received by the photodetector 22. Since the wavelength of the fault information is 1.53 μm, 80% of the optical power in the wavelength multiplexing coupler 3 is amplified by the optical fiber amplifier via the isolator 6 and guided to the output fiber 23. In addition, 20% of the optical power is detected by the photodetector 2.
2 leads to the detection of upstream failures.

Although not shown in the figure, a monitoring circuit such as a microcomputer is installed to capture the temperature of the excitation light sources 1 and 2, the output power, and the information of the photodetector 22. Further, the monitoring circuit may also perform an operation such as driving the semiconductor laser 21 to flow failure information downstream.

FIG. 2 shows another embodiment according to the present invention. The numbers in the figure are the same as those in FIG. In this embodiment, the disconnection of the input signal and the disconnection of the output signal can be detected. The signal light is light having a wavelength of 1.55 μm and intensity-modulated with a frequency f and a modulation factor of several percent. This signal can be obtained by direct modulation of the transmitting semiconductor laser, and it is also possible to suppress the stimulated Brillouin scattering of the transmission line fiber by setting f to a frequency of several KHz or higher. In the embodiment shown in FIG. 2, the optical fiber 25 is inserted into one end of the output of the wavelength division multiplexer 3, and the optical fiber 25
The excitation light of 48 μm is blocked. Then, the wavelength of 1.55 μm leaked by the wavelength multiplexing coupler 3 is converted into an electric signal by the photodetector 22, and the signal 27 of the frequency f is extracted by the bandpass filter 26. With such a configuration, it is possible to detect light with extremely high sensitivity, and it is possible to detect light of 1.55 μm with the crosstalk light of 1 to 2% of the wavelength multiplexing coupler 3. Further, the information on the obstacle having the wavelength of 1.53 μm can be taken out from 28. The output disconnection is detected by the photodetector 29 using the optical isolator 7.
The leak light such as is detected, and the signal of frequency f is extracted by the bandpass filter 30. Or output optical fiber 2
An optical coupler may be connected to 3 and a part of the output light may be extracted and input to the photodetector 29.

In a system in which an input break is detected and information about the occurrence of a failure is passed downstream by the semiconductor laser 21 as in this example, the optical fiber breaks even if the optical fiber breaks at one location. All optical repeaters installed downstream of the part will issue information on the occurrence of a failure. However, since the upstream signal can be received by the photodetector 22 even when the semiconductor laser 21 is operating, the monitoring circuit operates so as to immediately stop the failure occurrence signal of the own station when the failure occurrence signal is received from the upstream. Good.

[0016]

As described above, the optical repeater monitoring device according to the present invention can send and receive a fault signal without using an optical coupler, and therefore has the effect of not lowering the gain or output of the repeater. Moreover, since the number of parts is small, it is also suitable for downsizing and high reliability.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of an optical repeater monitoring device according to the present invention.

FIG. 2 is a diagram showing another embodiment of the optical repeater monitoring device according to the present invention.

FIG. 3 is a diagram showing an optical repeater monitoring device that can be easily inferred from the prior art.

FIG. 4 is a diagram showing an optical repeater device with a switch function that can be easily inferred from the prior art.

[Explanation of reference numerals] 1, ... Excitation light source 3,4 ... Wavelength multiplexing coupler 5 ... Erbium-doped optical fiber 6, 7 ... Optical isolator 21 ... Semiconductor laser 22 ... Photodetector 23 ... Downstream optical fiber 24 ... Upstream light fiber

Claims (5)

[Claims] 1. A rare earth element-doped fiber for amplifying signal light from the upstream side by injecting pumping light and outputting the amplified signal light to the downstream side, and one input end and one output end connected to the downstream side of the rare earth element-doped fiber. A 2-input / 2-output wavelength multiplexing coupler, a pumping light source connected to another input end of the wavelength multiplexing coupler to output the pumping light, and a pumping light wavelength connected to another output end of the wavelength multiplexing coupler An optical repeater comprising an optical transmitter that outputs a wavelength light between signal light wavelengths, wherein the optical transmitter transmits the wavelength light through the wavelength multiplexing coupler when a failure occurs in the optical repeater. The optical repeater monitoring device is characterized in that it is transmitted downstream. 2. A rare earth element-doped fiber for amplifying signal light from the upstream side by injecting pumping light and outputting the amplified signal light to the downstream side, and one input end and one output end connected to the downstream side of the rare earth element-doped fiber. A two-input two-output first wavelength multiplex coupler, a two-input two-output second wavelength multiplex coupler having one input end and one output end connected upstream of the rare earth element-doped fiber, and the first wavelength A pumping light source connected to the other input end of the multiplex coupler and the other input end of the second wavelength multiplex coupler to output the pumping light, and to another output end of the first wavelength multiplex coupler, An optical transmitter that outputs wavelength light between the pumping light wavelength and the signal light wavelength, and an optical receiver that is connected to the other output end of the second wavelength multiplexing coupler and receives the wavelength light from the upstream side. An optical repeater provided with the optical transmission The optical repeater monitoring device is characterized in that the optical transmitter transmits the wavelength light to the downstream via the wavelength multiplex coupler when a failure occurs in the optical repeater. 3. The optical repeater according to claim 2, wherein the signal light has a low frequency signal superimposed thereon, and the optical receiver detects the signal light by extracting the low frequency signal. Monitoring equipment. 4. The light according to claim 4, wherein a photodetector is provided downstream of the first wavelength multiplexing coupler, and the photodetector detects the signal light by extracting the low frequency signal. Repeater monitoring device. 5. The optical repeater monitoring device according to claim 2, wherein said optical receiver has an optical filter for blocking said pumping light wavelength.