JPH02241073A - Redundancy system of light source for pumping - Google Patents

Abstract

PURPOSE:To manufacture the title redundancy system in high reliability without augmenting the output of a pumping light source by a method wherein an optical signal propagating in an amplifier medium is converted into electric signal so as to identify the interruption of the optical signal and then the first and second light sources of pumping light are converted from each other conforming to the interruption data. CONSTITUTION:The title redundancy system of the pumping light source exciting an optical signal 11 propagating in an amplifying medium 6 (Er doped quartz base optical fiber) of an optical fiber doped with an rare earth element is provided with the first pumping light source 7 and the second pumping light source 8 respectively and independently arranged on both ends of the said amplifying medium 6, a photo detector 12 to convert the said pumping light propagating in the amplifying medium 6 or the optical signal 11 into electric signal, an interruption identifier 13 identifying the interruption of the pumping light or optical signal 11 using the electric signal from the photodetector 12. Through these procedures, the first and the second pumping light sources 7, 8 are converted from each other conforming to the interruption data of the interruption identifier 13 so that the optical signal may be excited by the pumping light.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a light source for pumping light used in an optical amplifier, an optical fiber laser, etc. in which an optical fiber is doped with a rare earth element, and particularly relates to a redundancy system for a light source for pumping light. It is something.

(Prior art and its problems) Until now, as a method for amplifying weakened optical signals in optical communication, the weak optical signal is converted into an electrical signal via a photodetector, and the electrical signal is equalized and After amplification and identification,
A method has been used in which an amplified electrical signal is converted into a strong optical signal via a semiconductor laser. On the other hand, there is a so-called optical direct amplification (hereinafter referred to as optical amplification) method that amplifies optical signals as they are. Since the optical amplification method does not use optical-electrical-optical conversion, it is possible to select or change the bit rate arbitrarily, perform batch amplification of wavelength-multiplexed optical signals and frequency-multiplexed optical signals, and also allows coherent amplification of intensity-modulated optical signals. Optical signals can also be amplified.

Therefore, when such an optical amplifier is used in an optical repeater, the entire system can be equivalently regarded as a type of extremely low-loss transmission line, so even in an optical communication system that has been installed several times, it is easy to replace terminal equipment. You will be able to upgrade your system at any time.

In this way, optical repeater technology using optical amplifiers has the potential to provide flexible and economical optical communication systems, so it is expected to be an indispensable technology for future optical communications and optical measurement. Research and development is actively conducted in each country.

One such optical amplifier is a method of amplifying light using an optical fiber doped with a rare earth element. 5μm
It has been confirmed that an optical amplifier (hereinafter referred to as "rEr-doped optical fiber laser amplifier") capable of amplifying signal light in the band by 20 to 30 dB can be obtained, and has a high saturation output level.
Due to its various advantages such as low polarization dependence and low noise figure, it is being actively researched as a future practical optical amplifier. The basic operating principle of an Er-doped optical fiber laser amplifier can be considered in the same way as a normal three-level laser using the electron energy level in the f-shell of Er. That is, as shown in FIG. 1, the ground state (ω.

), excited states 1 (ω, ) and 2 (ω2), and a ground state ω. and the ground state ω by absorbing light with energy (ω, −ω) corresponding to the energy level difference between the excited state ω and the excited state ω. The electrons that were in the state are excited to excited state 1. The electron excited to the excited state ω moves to the excited state ω2 by a non-emissive transition, and the ground state ω0 and the excited state ω
By emitting light having an energy corresponding to the energy level difference between 2 and 2 (frequency 2 = (ω2 - ω.)/h, where h is a blank constant), the electrons in excited state 2 are brought to the ground state. ω. However, if light with a frequency ν2 is incident at this time, the state changes from the excited state 2 to the ground state ω. Since the luminescence transition to occurs induced by the incident light, the frequency ν2
light can be amplified. In the case of Er, the frequency ν2
Since the wavelength of the light is in the 1.5 μm band, the Er-doped optical fiber laser amplifier can be used as an optical amplifier for 1.5 μm. When such an optical fiber laser amplifier is used in an optical repeater, it is necessary to provide a pumping (bumping) light source with a redundant configuration in order to improve the reliability of the repeater as a whole.

As shown in FIG. 2, the simplest redundant configuration is a method in which two pumping light sources are combined using a single mode optical fiber coupler. In Figure 2,
1 is an Er-doped silica optical fiber; 2 and 3 are light sources for bombing light; 4 is a multiplexer/demultiplexer that combines the pumping light and the signal light; 5 is a multiplexer that combines the light sources for bombing light;
20 is a single mode optical fiber serving as a transmission path.

(Problem to be Solved by the Invention) However, when multiplexing is performed using a multiplexer 5 using a symmetrical single-mode waveguide such as a beam splitter or a single-mode optical fiber coupler, after multiplexing by the multiplexer 5, Since the optical power of the pumping light source 2.3 becomes 1/2 of the output of each pumping light source, the output of each pumping light source 2.3 must be increased in order to obtain the necessary output power. Furthermore, since the reliability of a laser light source is generally inversely proportional to its optical output, there is a problem in that the reliability of the entire device is adversely affected.

The present invention has been made in order to solve the above-mentioned problems of the conventional technology, and an object of the present invention is to provide a highly reliable redundancy system for a light source for bombing light without increasing the output of the light source for bombing light. .

(Object of the Invention) The present invention is characterized in that, in a redundant system for a pumping light source in which pumping light excites an optical signal propagating in an amplification medium in which an optical fiber is doped with a rare earth element, The first independently placed
a bombing light light source and a second bombing light light source; a light receiver for converting the optical signal propagating in the amplification medium into an electrical signal; a determiner for determining disconnection of the disconnection; and excitation by the pumping light is performed by switching the first pumping light light source or the second pumping light light source from one to the other based on new information of the disconnection determiner. An object of the present invention is to provide a redundant system for a light source for bombing light, which is characterized by being configured as follows.

The present invention will be explained in detail below using examples.

(Example 1) FIG. 3 is a schematic diagram of a redundant system of a light source for bombing light in the present invention, where 6 is an Er-doped quartz optical fiber, 7.8 is a light source for bombing light, and 9.10 is a pumping light source. A multiplexer/demultiplexer that multiplexes and demultiplexes light and signal light; 11 is a signal light;
12 is a light receiver that converts the signal light 11 into an electrical signal; 13 is a disconnection detector that determines that the signal light 11 is disconnected when it is below a predetermined level for a certain period of time; and 14 is a received output signal. be. For example, if the Er-doped silica optical fiber 6 is excited using the bombing light source 7, the receiving side will detect an abnormality in the bombing light source 7 by the disconnection detector 13. 7 stops, and the Er-doped quartz optical fiber 6 is excited by the bombing light source 8.By switching the bombing light source, the traveling directions of the signal light 11 and the pump light are reversed. It is possible to make the amplification characteristics almost the same by adjusting the appropriate optical fiber length and pumping power, for example, in accordance with the amplification characteristics of the system optical fiber 6. By inserting the multiplexer/demultiplexer 10, the insertion loss of the optical amplifier itself increases compared to the case shown in Fig. 1, but this is very small and is not a major drawback. Light wavelength is 1.46μm
In this case, if an optical fiber coupler is used, the insertion loss will be about 0.5 dB or less.

Note that when the multiplexer/demultiplexer 10 is inserted between the multiplexer/demultiplexer 9 and the Er-doped silica optical fiber 6, the pumping light from the pumping light light source 7 is directed to the Er-doped silica optical fiber 6 side. The light does not enter and exits from another port of the multiplexer/demultiplexer 10, making it useless for practical use. Therefore, the multiplexer/demultiplexer 10 for multiplexing the preliminary bombing light source 8 needs to be placed on the output end side of the Er-doped silica optical fiber 6.

(Embodiment 2) FIG. 4 is a second embodiment of the present invention, and is a schematic diagram of a redundant system of a light source for bombing light.

The difference from Embodiment 1 is that the pumping light sources 7 and 8 can be alternately switched based on new information about the pumping light. This is a branching filter whose branching ratio (for example, a branching ratio of 1:99) is set so as to extremely reduce the amount of pumping light applied to the side.

In FIG. 4, the pumping light emitted from the pumping light light source 7 (8) is sent to the demultiplexer 15 (15').

Multiplexer/demultiplexer 9 (10), Er-doped silica optical fiber 6
, is converted into an electric signal by the optical receiver 12 (12') via the multiplexer/demultiplexer 10 (9) and the demultiplexer 15 (15'). 13, and the other bombing light light source 8 (7
) is turned on to make it work.

In addition, in the above explanation, a configuration was shown in which the bombing light source 7 (8) is multiplexed and demultiplexed at the single mode optical fiber 20, but the E
Signal light 11 is absorbed by r-doped silica optical fiber 6
It is also possible to perform multiplexing and demultiplexing at both ends of the Er-doped silica optical fiber 6, although the level of .

That is, this multiplexing and demultiplexing is performed using the Br-doped silica optical fiber 6.
This will be done at appropriate locations on both ends of the .

Although the Er-doped silica optical fiber has been described above as an optical amplifier, the same bombing technique can be applied even when the Er-doped optical fiber is used as a laser oscillator. In addition, Nb (niodium) other than Er, H
Similar bombing techniques can be applied to rare earth elements such as o (phorium) and Tm (1-lium) as dopants, or to fluoride optical fibers.

(Effects of the Invention) The present invention provides a bombing method that can make the most effective use of the optical output of the light source for bombing light by making a disconnection determination after converting it into an electrical signal on the receiving side and switching the light source for bombing light on the receiving side. This enables a redundant configuration of light sources for light. As a result, the load on the bombing light source can be reduced, and the credibility of the entire device can be significantly improved. Therefore, the present invention can be applied to the fields of optical relay systems and optical measurement using a pumping light source, and its effects are extremely large.

[Brief explanation of drawings]

Fig. 1 is an energy state diagram for explaining the operating principle of a conventional Er-doped optical fiber laser amplifier, Fig. 2 is a schematic configuration diagram of a redundant system of a conventional bombing light source, and Fig. 3
4 are schematic configuration diagrams showing respective embodiments of a redundant system of a light source for bombing light according to the present invention. 1.6...Er-doped silica optical fiber, 2.3,7
．． 8... Light source for bombing light, 4.9.10... Multiplexer/demultiplexer, 5... Multiplexer, 11... Optical signal, 12
．． 12"... Light receiver, 13... Disconnection determiner, 14.
...output signal, 15.15' ...brancher, 20.
...Single mode optical fiber.

Claims (1)

[Claims] In a redundant system for a pumping light light source that uses pumping light to excite an optical signal propagating in an amplification medium in which an optical fiber is doped with a rare earth element, the pumping light source is arranged independently at both ends of the amplification medium. a first pumping light light source and a second pumping light light source; a light receiver for converting the pumping light or optical signal propagating within the amplification medium into an electrical signal; and an electrical signal from the light receiver. a disconnection determiner that determines disconnection of the pumping light or optical signal using the disconnection determiner; and switching the first pumping light light source and the second pumping light light source from one to the other based on new information of the disconnection determiner. A redundant system for a light source for pumping light, characterized in that the pumping light source is configured to perform excitation by the pumping light.