JP2795544B2 - Fiber type optical amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fiber type optical amplifying apparatus using an optical fiber doped with rare earth element ions exhibiting an optical amplifying action by optical excitation.

[0002]

2. Description of the Related Art In recent years, the core of a silica-based optical fiber has Er
Research on optical fibers using a light amplification effect at the time of photoexcitation of these ions by mixing ions of rare earth elements such as N and Nd has been actively conducted. For example, a quartz-based single mode mixed with several tens to 100 ppm of Er ions
Wavelength 1450 n generated from an excitation light source (for example, a semiconductor laser) in a doped optical fiber (Er dope fire bar).
When pump light of m to 1540 nm is input through an optical multiplexer, signal light of 1530 to 1650 nm can be amplified.

[0003] In the case of Er-doped fiber, even if the wavelength of the pump light is near 980 nm, it is promising. Further, the optical amplification effect can be exerted even in a fiber mixed with a rare earth element or transition metal other than Er.

This optical fiber can be combined with other optical members to form a fiber-type optical amplifier as shown in FIG. In the fiber type optical amplifying device shown in FIG. 4, an excitation light sent from an excitation light source 11 such as a semiconductor laser and a signal light input from an input terminal 12 to an optical fiber 13 are multiplexed by an optical fiber coupler 14. The rare earth element ions are guided to the doped optical fiber 15, and the rare earth element ions are optically excited by the excitation light to amplify the signal light. In FIG. 4, 16 is an optical isolator, and 17 is an output terminal. The optical isolator 16 and the optical fiber 15 are fused or connected at a connection point O.

[0005]

However, the pumping light source may decrease the output of the pumping light due to deterioration with time, or may not output the pumping light at all due to damage. In such a case, the rare earth element ions in the optical fiber are not sufficiently excited or not excited at all, so that the optical amplification of the optical fiber is also insufficient.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide two or more excitation light sources so that even if one of the excitation light sources does not operate normally, a level sufficient to excite the rare earth element of the optical fire is obtained. An object of the present invention is to realize a fiber-type optical amplifying device capable of obtaining pump light.

[0007]

According to the present invention, there is provided a fiber type optical amplifier comprising an optical fiber doped with rare earth element ions.
As shown in FIG. 1, two or more excitation light sources 2 for generating the excitation light for exciting the rare earth element ions and amplifying the signal light a supplied to the optical fiber 1 are provided, as shown in FIG.
The pumping light from each pumping light source 2 is input to one fiber coupler 5, and the total pumping light input in the fiber coupler 5 is equally divided by the number of outputs n (for example, the number of inputs is 8, the distributed optical fiber 8 for 1: 8/8 when the number of outputs is 8)
And distributed to each optical fiber 1, the output light level from any one of the two or more optical fibers 1 is monitored by one monitoring light detection unit 3, and according to the monitoring result. One control unit 4 controls the drive current supplied to each excitation light source 2 to control the level of the excitation light output from the excitation light source 2 and to stabilize the output light level from the optical fiber 1. It was made.

[0008]

In the fiber type optical amplifier of the present invention, the excitation light from two or more excitation light sources 2 is equally divided by the output number n by one fiber coupler 5 and distributed to each optical fiber 1. Even if the level of the pumping light output from one of the pumping light sources 2 falls below a predetermined value, all the pumping lights input from some of the other pumping light sources 2 are equally divided by the number of outputs n and each light is output. Since the light is distributed to the fibers 1, the level of the pump light distributed to each optical fiber 1 does not decrease so much. Incidentally, when the number of inputs of the pumping light (the number of the pumping light sources 2) input to the fiber coupler 5 is eight and the number of the optical fibers 1 to which the pumping light is distributed from the fiber coupler 5 is eight,
The excitation light energy distributed to each optical fiber 1 is 8/8 during normal operation, but only (8-1) / 8 when any one of the excitation light sources 2 does not operate normally. Therefore, the level of the pumping light distributed to each optical fiber 1 does not decrease so much. Further, since the reduced level is equally borne by the other excitation light sources 2, the load on each of the excitation light sources 2 is not so large. Moreover,
Automatic gain control (AGC) is performed so that the level of the pumping light output from the pumping light source 2 becomes constant in accordance with the result of monitoring by the monitoring light detection unit 3, and returns to the original pumping light level. The burden on the other excitation light source 2 is temporary, and the burden is immediately eliminated.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 showing one embodiment of a fiber type optical amplifier of the present invention, reference numeral 1 denotes an optical fiber, 2 denotes a pumping light source,
Reference numeral 3 denotes a monitor light detection unit, 4 denotes a control unit, and 5 denotes a fiber coupler.

The optical fiber 1 contains a mixture of rare earth element ions such as Er and Nd, for example, 5 Er ions.
A single mode fiber doped with 30 ppm is used. The excitation light source 2 has, for example, an oscillation wavelength of 1470 to
A 1480 nm semiconductor laser is used.

The fiber coupler 5 distributes pump light at a level obtained by equally dividing the total pump light input from the two or more pump light sources 2 by the number of outputs n to each optical fiber 1.
As the fiber coupler 5, for example, a tree star coupler as shown in FIG. 3 is used. This fiber coupler 5
The pump light input from the eight input terminals 1 to 8 is sequentially distributed from the former-stage distributor 6 to the latter-stage distributor 6 among the three-stage connected distributors 6, and all of the third-stage Distributor 6
Are designed to output the same level of excitation light. Each output end of the fiber coupler 5 is coupled to the input side of each optical fiber 1 by an optical multiplexer 21 such as a polarization coupler or a mechanical switch as shown in FIG. Light is transmitted to each optical fiber 1.

The monitoring light detecting section 3 is for taking out a part of the output light of the optical fiber 1 and detecting its level, and for example, a fat diode PD is used. The monitoring light detector 3 is connected to the optical fiber 1 by an optical demultiplexer 22, as shown in FIG. 2, so that a part of the output light b of the optical fiber 1 can be extracted.

The control section 4 controls the drive current supplied to each of the two or more excitation light sources 2 in accordance with the monitoring result of the monitoring light detection section 3 so that the excitation light output from the excitation light source 2 is controlled. Of the optical fiber 1, thereby controlling the optical amplification in the optical fiber 1 to stabilize the level of the optical output b output from the optical fiber 1.

[0014]

The fiber type optical amplifier of the present invention has the following effects. . Even if any of the excitation light sources 2 does not operate normally, the level of the excitation light transmitted to each optical fiber 1 is stabilized. . Even if one of the excitation light sources 2 does not operate normally and the level is reduced, the reduction is equally borne by the other excitation light sources 2, so that the load on the individual excitation light sources 2 is not so large. . Since the automatic gain control is performed so that the level of the pumping light output from the pumping light source 2 becomes constant, the load on the other pumping light sources 2 is temporary, and the load is immediately eliminated. . Even if there are two or more optical fibers 1 and two or more excitation light sources 2, only one monitoring light detection unit 3 and one control unit 4 are required, which is economical.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a fiber type optical amplifying device of the present invention.

FIG. 2 is an explanatory diagram showing a coupling state of an optical fiber, a fiber coupler, and a monitoring light detection unit in the fiber optical amplifier of the present invention.

FIG. 3 is an explanatory diagram showing an example of a fiber coupler used in the fiber optical amplifier of the present invention.

FIG. 4 is an explanatory view showing an example of a conventional fiber-type optical amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical fiber 2 Light source for excitation 3 Light detection part for monitoring 4 Control part 5 Fiber coupler

Claims (1)

(57) [Claims] 1. An optical fiber 1 doped with rare-earth element ions, two or more of which are provided to excite the rare-earth element ions to generate excitation light for amplifying signal light a supplied to the optical fiber 1. Two or more light sources 2 are provided, and each excitation light source 2
Is input to one fiber coupler 5 and the total number of outputs is n
The output light level from any one of the two or more optical fibers 1 is monitored by one monitoring light detection unit 3 and divided into two or more optical fibers 1. The drive current supplied to each excitation light source 2 is controlled by one control unit 4 according to the monitoring result to control the level of the excitation light output from the excitation light source 2 and the output light from the optical fiber 1. A fiber type optical amplifying device characterized in that the level is stabilized.