JP2001308422A - Excitation light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an excitation light source device which enables to multiplex the excitation light of many wavelengths and output with high power. SOLUTION: This excitation light source device consists of excitation light sources 1 each of which outputs an excitation light of a different wavelength from the others, and a wavelength multiplexer 2 each of which multiplexes a light of a different wavelength from the others. Each excitation light source 1 is provided with a laser diode 101a through 108b, and an excitation light output fiber 8 which forms a gratings 22 reflecting light of a different wave length from each other. To four light input parts 201, 202, 207 and 208 of the wavelength multiplexer 2, light output parts of a polarized synthesizer 3 which multiplexes two polarized wave lights with different polarized wave states from each other are connected, respectively. To the light output part of each polarized wave synthesizer 3, the two excitation light sources 1 which output polarized light with different polarized wave state and different wave length from the other are connected, respectively. The excitation light sources 1 are connected to light input parts 203, 204, 205 and 206.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an excitation light source device applied to an optical amplifier for optical communication, and more particularly to an optical amplification device used in a wavelength division multiplex transmission system or an optical submarine transmission system having a long transmission distance. The present invention relates to an excitation light source device for an apparatus.

[0002]

2. Description of the Related Art In recent years, wavelength division multiplex transmission systems have been actively studied. The wavelength division multiplexing transmission system is a system for multiplexing a plurality of optical signals of different wavelengths on a single optical fiber as an optical transmission line and transmitting the multiplexed signals. .

In a wavelength division multiplexing transmission system, an optical amplifier is provided in the middle of an optical transmission line, and transmission is performed while amplifying transmission light (optical signal) by the optical amplifier. As an optical amplifier, it is effective to use an optical fiber type optical amplifier which can amplify an optical signal as it is. Currently, an erbium-doped optical fiber type optical amplifier (EDF) using an erbium-doped optical fiber is used.
A) is commonly used.

In the wavelength division multiplexing transmission system, attempts have been made to increase the degree of wavelength multiplexing to increase the amount of transmission. One way to increase the degree of wavelength multiplexing is to expand the wavelength band. ing.

However, the above-mentioned EDFA used for a wavelength division multiplexing transmission system generally has a maximum of 30.
The gain band of the EDFA is at most 60 n even if the gain band of the EDFA is extended to the longer wavelength side by increasing the length of the erbium-doped optical fiber.
m. Moreover, since the gain of the EDFA has wavelength dependence, and the gain flatness in the gain band is not good, when the EDFA is applied to a wavelength division multiplexing transmission system, a gain flattening device for flattening the gain of the EDFA is used. There was also a problem that required.

Therefore, recently, as an optical amplifier replacing the EDFA, a Ram using an optical fiber with high nonlinearity has been used.
An amplifying optical amplifier has been attracting attention. This Raman
The amplification type optical amplifier utilizes the Raman effect that occurs when strong pump light is input to an optical fiber having high nonlinearity.

In order to realize Raman amplification with good gain flatness, it is necessary to multiplex a plurality of pump lights having different wavelengths at a narrow frequency interval of about 1 THz. By inputting to an optical fiber having high performance, Rama having high gain over a wide band of 100 nm or more without using a gain flattening device.
An n-amplification type optical amplifier can be realized.

As an example of an apparatus using Raman amplification, for example, a known document “Y. Emori et al., OFC'99 PD-19”
Discloses an example in which a wavelength interval of 7.5 nm and a wavelength interval of 15 nm are interwoven to multiplex 12 different wavelengths of light in a wavelength range of 1405 nm to 1510 nm.

The configuration of the pump light source device used for the wavelength multiplexing is shown in FIG.
2 wavelengths (λ1, λ2,..., Λ12 in the figure)
, And a wavelength multiplexer 2 for multiplexing the light of the above-mentioned wavelength output from each of the excitation light sources 1.

The wavelength multiplexer 2 has a plurality of Mach-Zehnder interference type multiplexing means 6 as shown in FIG.
The Mach-Zehnder interference type multiplexing means 6 is formed by two arms (optical paths) 35 as shown in FIG.
Light of different wavelengths (λa and λb in the figure) incident from the two incident-side transmission lines 5a and 5b are multiplexed and transmitted to one emission-side transmission line 5c. FIG.
The wavelength multiplexer 2 shown in FIG. 3 is formed by an optical waveguide circuit. In this case, the arm 35 is formed by a core of the optical waveguide circuit.

As shown in FIG. 14, two directional couplers 12 and their directional couplers 12 are provided between the input-side transmission lines 5a and 5b and the output-side transmission line 5c of the Mach-Zehnder interference type multiplexing means 6. An optical path length difference portion 13 sandwiched between the couplers 12 is formed. In the optical path length difference portion 13, the lengths of the two arms 35 are different from each other. Arm 3 in optical path length difference section 13
The wavelength interval of the light to be multiplexed by the Mach-Zehnder interference type multiplexing means 6 is determined by the difference in the lengths of the five.

As shown in FIG. 13, the wavelength multiplexer 2
Has a plurality of first-stage Mach-Zehnder interference type multiplexing means 6 having the above configuration on the light incident side (six in FIG. 1), and a pair of these first-stage Mach-Zehnder interference type multiplexing means are provided. The second stage Mach-Zehnder interference type multiplexing means 6 for further optically multiplexing the optical output of the means 6 is connected. The optical multiplexing means is formed by connecting a total of 11 Mach-Zehnder interference type multiplexing means 6 in four stages.

[0013]

By the way, in the Mach-Zehnder interference type multiplexing means 6 constituting the wavelength multiplexer 2, it is necessary to pay attention to the design of the directional coupler 12. That is, since the coupling efficiency of the directional coupler 12 has wavelength dependence, the coupling efficiency of the Mach-Zehnder interference type multiplexing means 6 to the optical input section (cross port) 30 on the side crossing the output section 32 is increased. Directional coupler 12 of the input wavelength
If the coupling efficiency is not set to around 50%, the loss will increase. In addition, this is a registered patent No. 2.
557966.

However, in the wavelength multiplexer 2 of the pump light source device as shown in FIG. 13, the number of Mach-Zehnder interference type multiplexing means 6 forming the wavelength multiplexer 2 is 11
The number of stages is four, and the wavelength to be multiplexed by one Mach-Zehnder interference type multiplexing means 6 becomes complicated, and the coupling efficiency becomes 5
It is difficult to design such that it is close to 0%.

In the wavelength multiplexer 2 applied to the above-mentioned pumping light source device, the number of connection stages of the Mach-Zehnder interference type multiplexing means 6 is large. Since the bandwidth of each wavelength multiplexed by the wavelength multiplexer 2 becomes narrower as the number of stages of the Mach-Zehnder interference type multiplexing means 6 increases, in the wavelength multiplexer 2 having a large number of connection stages of the Mach-Zehnder interference type optical multiplexer 6. Is that only a part of the spectrum width (bandwidth) of each pump light can pass through the wavelength multiplexer 2 and the insertion loss of the wavelength multiplexer 2 is large. Is reduced.

Therefore, the Raman amplification type optical amplifier using the above wavelength multiplexer 2 cannot improve the Raman amplification efficiency.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to combine pumping lights of a number of wavelengths so as to improve the Raman amplification efficiency of a Raman amplification type optical amplifier. And to provide an excitation light source device capable of outputting a high output.

[0018]

In order to achieve the above-mentioned object, the present invention has the following structure to solve the problem. That is, the first invention has a wavelength multiplexer for multiplexing lights of a plurality of wavelengths different from each other, and two or more optical input units of the wavelength multiplexer have two polarization states different from each other. An optical output section of a polarization combiner for multiplexing polarized lights is connected to the optical input section of the polarization combiner, and two pump light sources for outputting polarized lights having different polarization states and wavelengths from each other are connected to the optical input section. The above configuration is used as means for solving the problem.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the wavelength multiplexer multiplexes lights having different wavelengths respectively incident from two incident-side transmission lines to form one light. Having a plurality of first-stage optical multiplexing means for transmitting light to the output side optical transmission line,
The second stage optical multiplexing means for further multiplexing the optical output of each pair of optical multiplexing means of the first stage is connected, and the optical output of the optical multiplexing means of the preceding stage is further optically multiplexed by the latter optical multiplexing means. In order to solve the problem, the optical multiplexing means is formed by connecting the optical multiplexing means in a plurality of stages.

Further, according to a third aspect of the present invention, in addition to the configuration of the second aspect of the invention, the multiplexed light center wavelengths multiplexed by the respective optical multiplexing means have their own periods.
A configuration in which the unique period of the optical multiplexing means provided in the (n-1) th stage (n is an integer of 2 or more) is an integral multiple of the unique period of the optical multiplexing means provided in the nth stage. Is a means to solve the problem.

Further, the fourth invention is directed to the second or third embodiment.
In addition to the configuration of the invention, the optical multiplexing means is a means for solving the problem by a configuration of a Mach-Zehnder interference type multiplexing means having two directional couplers.

In a fifth aspect of the present invention, in addition to the configuration of the fourth aspect, the directional coupler is a means for solving the problem by having a configuration in which the directional coupler is a fused fiber coupler.

According to a sixth aspect of the present invention, in addition to the configuration of the fourth aspect, the Mach-Zehnder interference type multiplexing means solves the problem by a configuration formed by an optical waveguide circuit.

Further, the seventh invention is directed to the second or third embodiment.
In addition to the configuration of the present invention, the optical multiplexing means is a means for solving the problem by having a configuration of a fused fiber coupler.

In the present invention having the above-described structure, two polarized lights having different polarization states are multiplexed to one or more optical input sections of a wavelength multiplexer for multiplexing lights having different wavelengths. A polarization combiner is connected, and two excitation light sources that output polarized lights having different polarization states and wavelengths from each other are connected to the polarization combiner. Therefore, polarized lights output from the two excitation light sources are respectively connected. The signals are multiplexed by the polarization combiner and input to the wavelength multiplexer.

In the configuration of the conventional pumping light source device as shown in FIG. 13, the number of optical input sections provided in the wavelength multiplexer depends on the number of wavelengths multiplexed by the wavelength multiplexer (12 in FIG. 13).
However, in the present invention, the polarized lights having different polarization states and wavelengths are multiplexed by the polarization combiner, and the multiplexed light is transmitted from one or more optical input units of the wavelength multiplexer. Since the light is input to the wavelength multiplexer, for example, as shown in FIG. 1, when the number of pumping light sources is the same, the number of optical input units provided in the wavelength multiplexer is reduced by the number of polarization combiners. It is possible to do.

In particular, a wavelength multiplexer generally formed by connecting a plurality of optical multiplexing means such as a Mach-Zehnder interference type multiplexing means is generally used. When the number of optical input sections increases, the number and the number of stages of the optical multiplexing means must be increased accordingly, and the increase in the insertion loss of the wavelength multiplexing device is a problem, but in the present invention, Since the number of optical input units provided in the wavelength multiplexer can be reduced by the number of polarization combiners,
The number and the number of optical multiplexing means forming the wavelength multiplexer can be reduced, and the problem of narrowing the wavelength bandwidth of the multiplexed light, which has been a problem in the wavelength multiplexer having a large number of stages, can be reduced. The insertion loss of the wave device can be significantly reduced.

Therefore, the present invention makes it possible to provide a pumping light source device capable of multiplexing pumping lights of many wavelengths and outputting a high output, thereby improving the Raman amplification efficiency of the Raman amplification type optical amplifier. Can be achieved.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same reference numerals are given to the same parts as those in the conventional example, and the overlapping description will be omitted. FIG. 1 shows a first embodiment of the excitation light source device according to the present invention.

As shown in the figure, the excitation light source device of the present embodiment, different wavelengths (λ _{1 a,} λ _1b,
lambda _2a, the excitation light source 1 of a plurality (12 pieces in the drawing) that outputs pumping light · · · lambda _8b), and a wavelength multiplexer 2 for multiplexing light of different wavelengths from each other . Each excitation light source 1 is composed of laser diodes 101a, 102b,.
8b and a pumping light output fiber 8, and each of the pumping light output fibers 8 has a grating (fiber grating) that reflects light having the above-mentioned different wavelength from each other.
22 are formed.

One or more wavelength multiplexers 2 (four in the figure)
Optical input units (input ports) 201, 202, 207, 2
08 is connected to an optical output unit of a polarization combiner 3 that combines two polarized lights having different polarization states from each other via an optical input fiber 9 and a depolarizer 5. Each of the optical input sections of these polarization combiners 3 has two pumping light sources 1 that output polarized lights having different polarization states and wavelengths.
Are connected to each other.

The two excitation light sources 1 connected to the respective polarization combiners 3 are configured so that one outputs a linearly polarized light and the other outputs a horizontally polarized light. Also,
Since the polarization combiner 3 has a function of multiplexing, with low loss, the polarization of the band including the light of the wavelength output from the corresponding two pumping light sources 1, the polarization combiner 3 The combination of the horizontal polarization and the vertical polarization is performed with very low loss.

Further, in the present embodiment, the depolarizer 5 is provided on the output side of the polarization
The polarization state of the linearly polarized light and the horizontally polarized excitation light that has been polarization-combined by the polarization combiner 3 is set to a non-polarization state, and the polarization-dependent loss of the wavelength multiplexer 2 is reduced by the wavelength multiplexer 2. The effect on the multiplexed light is suppressed.

The pumping light source 1 is connected to each of the remaining optical input sections (input ports) 203, 204, 205, and 206 of the wavelength multiplexer 2 via an optical input fiber 9. . In this embodiment, the light input unit 20 is used.
Light from the excitation light source 1 connected to 3, 204, 205, and 206 is also in a non-polarized state.

The reflected light wavelengths of the gratings 22 formed in the respective excitation light sources 1 have different wavelengths λ _1a and λ
_1b , λ _2a ,..., Λ _8b , and each grating 22 functions as an external resonator of the corresponding laser diode 101a, 102b,. Thus, grating 2
2 function as an external resonator, the reflected light wavelengths (λ _1a , λ _1b ,
λ _2a, ··· λ _8b) and the possible output with a narrow oscillation spectrum width from each of the pumping light source 1, and it is assumed stable output of each of the pumping light source 1.

The wavelength multiplexer 2 is, as shown in FIG.
Flame deposition (eg N. Takato etal, J. Lightwave Te
ch., vol16, pp. 1003-1010, 1988).
Lower clad layer 18 and core circuit 1 on silicon substrate 19
0 are formed in order, and the optical waveguide circuit is formed by embedding the core circuit 10 with the upper cladding layer 17. The detailed description of the method of forming the optical waveguide circuit by the flame deposition method is omitted.

As shown in FIG. 1, the core circuit 10 has a plurality of Mach-Zehnder interference type multiplexing means 6 as optical multiplexing means forming the wavelength multiplexer 2, and the optical input sections 201 to 208
The first stage Mach-Zehnder interference type multiplexing means 6 (6c1
To 6c4) are arranged in parallel.

A second stage Mach-Zehnder interference type multiplexing means 6 (6b1, 6b1) for further optically multiplexing the optical output of each pair of Mach-Zehnder interference type multiplexing means 6 among these Mach-Zehnder interference type multiplexing means 6 6b2) to connect the preceding pair of Mach-Zehnder interference type multiplexing means 6 (in this case, 6
In the present embodiment, a total of seven Mach-Zehnder interference type multiplexing means 6 are provided such that the optical outputs c1 to 6c4) are further optically multiplexed by the Mach-Zehnder interference type multiplexing means 6 (6b1 and 6b2 in this case) at the subsequent stage. (6a to 6c4) are connected in a plurality of stages (here, three stages) to form the core circuit 10.

In this embodiment, the multiplexed light center wavelengths multiplexed by the respective Mach-Zehnder interference type multiplexing means 6 have their own periods, and (n−
1) The inherent period of the Mach-Zehnder interference type multiplexing means 6 provided at the stage (n is an integer of 2 or more) is an integral multiple of the inherent period of the Mach-Zehnder interference type multiplexing means 6 provided at the n-th stage. Has formed.

Specifically, the specific period of the second-stage Mach-Zehnder interference type multiplexing means 6b1 and 6b2 is two times the specific period of the third-stage Mach-Zehnder interference type multiplexing means 6a.
In addition, the inherent period of the Mach-Zehnder interference type multiplexing means 6c1 to 6c4 provided in the first stage is Mach-Zehnder interference type multiplexing means 6b1 and 6b provided in the second stage.
2 which is twice the inherent period.

The inherent period of the center wavelength of the multiplexed light multiplexed by the Mach-Zehnder interference type multiplexing means 6 is determined by the design of the wavelength multiplexer 2 shown below. Hereinafter, a method of designing the wavelength multiplexer 2 in the present embodiment will be briefly described.

As described above, the basic configuration of the Mach-Zehnder interference type multiplexing means 6 is as shown in FIG. 14, and the Mach-Zehnder interference type multiplexing means 6 shown in FIG. Of the incident light, light wavelengths (combined light center wavelengths that can be multiplexed with low loss by the Mach-Zehnder interference type multiplexing means 6) λa and λb output from the emission side transmission line 5c with low loss are as follows, respectively. This is the wavelength represented by the equation.

Λa = n · ΔL / m (1)

Λb = n · ΔL / (m + ／) (2)

Here, n is the refractive index of the optical transmission path, ΔL is the optical path length difference, and m is an integer. In addition, the light input part 30 of the incident side transmission line 5a that intersects the emission side transmission line 5c and the light output part 32 is called a cross port as described above, and the light input part 31 of the non-intersecting incident side transmission line 5b passes through. Called port.

From equations (1) and (2), the multiplexed wavelength of the Mach-Zehnder interference type multiplexing means 6 periodically appears at a constant frequency interval Δf, where c is the speed of light, as in equation (3).

Δf = c / (2n · ΔL) (3)

FIG. 6A shows an example of the light transmission wavelength characteristic of the Mach-Zehnder interference type multiplexing means 6 shown in FIG. In the Mach-Zehnder interference type multiplexing means 6,
At equal frequency intervals Δf as shown in equation (3), for example, FIG.
As shown by the characteristic lines a and b in FIG. 1A, a low-loss peak appears, and as shown by the characteristic line a, the cross port (FIG. 1)
4, the low-loss peak wavelengths in the transmission wavelength characteristics of the light input from the optical input unit 30) are λ _a1 , λ _a2 ,
λ _a3 , λ _a4 , ... (peak frequency interval is 2 · Δ
f). The characteristic line b in FIG. 14A shows the transmission wavelength characteristic of the light input from the through port (the optical input unit 31 in FIG. 14).

This Mach-Zehnder interference type multiplexing means 6
As shown in FIG. 5, the Mach-Zehnder interference type multiplexing means 6a
If it is provided on the output unit 14 side of the wavelength multiplexer 2,
The Mach-Zehnder interference type multiplexing means 6 a
(Crossport) to Mach-Zehnder interference type multiplexing means 6
wavelengths λ _a1 , λ _a2 , λ _a3 , λ _a4 ,
.. Are multiplexed and output from the optical output unit 14.

When the Mach-Zehnder interference type multiplexing means 6b is connected to the preceding stage of the Mach-Zehnder interference type multiplexing means 6a as shown in FIG. By designing the length difference ΔL to be half of the optical path length difference in the succeeding Mach-Zehnder interference type multiplexing means 6a, the frequency interval Δf of the preceding Mach-Zehnder interference type multiplexing means 6b is reduced to 2 Can be doubled.
Then, the light transmission characteristic of the Mach-Zehnder interference type multiplexing means 6b becomes the characteristic shown in FIG.

In FIG. 6B, a characteristic line a is a transmission wavelength characteristic of light input from the cross port (the optical input unit 501 in FIG. 5), and a characteristic line b is a through port (FIG. 5). The Mach-Zehnder interference type multiplexing means 6b shows the transmission wavelength characteristics of the light input from the light input unit 502), and the light of the wavelengths λ _a1 , λ _a3,. The light of wavelengths λ _a2 , λ _a4 ,... Input from the light input unit 502 can be combined and output.

The Mach-Zehnder interference type multiplexing means 6
b and the Mach-Zehnder interference type multiplexing means 6a, the optical output unit 1
The transmission wavelength characteristic of the light output from FIG. 4 is the characteristic shown by the characteristic line a in FIG. 6C, and the wavelengths λ _a1 , λ _a3,.
Are multiplexed with low loss and output. The transmission wavelength characteristic of light input from the light input unit 502 and output from the light output unit 507 is represented by a characteristic line b in FIG.
, And light of wavelengths λ _a2 , λ _a4 ,... _Are multiplexed with low loss and output.

The Mach-Zehnder interference type multiplexing means 6b
When the Mach-Zehnder interference type multiplexing means 6 is further connected to the preceding stage, the inherent period of the Mach-Zehnder interference type multiplexing means 6 is determined in the same manner as described above, and the optical path length difference is determined correspondingly.

As described above, when designing the wavelength multiplexer 2,
Among the Mach-Zehnder interference type multiplexing means 6 constituting the wavelength multiplexer 2, the output light from all the pumping light sources 1 connected to the wavelength multiplexer 2 by the Mach-Zehnder interference type multiplexing means 6 on the optical output unit 14 side. Is determined by the Mach-Zehnder interferometer-type multiplexing means 6 so that the optical path of the Mach-Zehnder interferometer-type multiplexing means 6 is determined in accordance with this period. The length difference ΔL is determined, and the Mach-Zehnder interference type multiplexing means 6 connected before the Mach-Zehnder interference type multiplexing means 6 is as follows.
As described above, the specific period and the optical path length difference are sequentially determined.

Then, the wavelength multiplexer 2 capable of multiplexing the output light from all the pumping light sources 1 connected to the wavelength multiplexer 2 with low loss is formed.

In the present embodiment, the center wavelength of the multiplexed light to be multiplexed by the respective Mach-Zehnder interference type multiplexing means 6 forming the wavelength multiplexer 2 is determined as described above. When the light input from the unit 201 passes through the Mach-Zehnder interference type multiplexing means 6c1, 6b1, and 6a in order, and is output from the light output unit 14, the light transmission characteristics are as shown in FIG. I made it. As is apparent from this characteristic, the wavelengths λ _1a , λ
_When the light of _1b is input, the lights of these wavelengths are multiplexed with low loss by the wavelength multiplexer 2 and output from the optical output unit 14.

Similarly, the light input from the light input unit 202 is transmitted to the Mach-Zehnder interference type multiplexing means 6c1, 6b1, 6a.
The light transmission characteristics when the light is output from the light output unit 14 in the order shown in FIG. 4B are as shown in FIG. 7B. In the present embodiment, the light having the wavelengths λ _2a and λ _2b is transmitted from the light input unit 202. Are input by the wavelength multiplexer 2 with low loss and output from the optical output unit 14.

Similarly, (c) and (d) of the figure show that the light input from the optical input unit 203 and the light input from the optical input unit 204 are respectively connected to the Mach-Zehnder interference type multiplexing means. 6c2, 6b1, 6a, and the light output unit 1
4 shows the light transmission characteristics when output from FIG. In the present embodiment, when light of wavelength λ ₃ is input from the optical input unit 203 and light of wavelength λ ₄ is input from the optical input unit 204, the light of these wavelengths is reduced in loss by the wavelength multiplexer 2. And output from the optical output unit 14.

FIGS. 4A and 4B show the light input from the light input unit 205 and the light input unit 20 respectively.
The light transmission characteristics when the light input from 6 is output from the light output unit 14 through Mach-Zehnder interference type multiplexing means 6c3, 6b2, 6a in order are shown. In the present embodiment, when light of wavelength λ ₅ is input from the optical input unit 205 and light of wavelength λ ₆ is input from the optical input unit 206, the light of these wavelengths is reduced in loss by the wavelength multiplexer 2. And output from the optical output unit 14.

Further, (c) of FIG.
The light input from the Mach-Zehnder interference type multiplexing means 6
The light transmission characteristics when the light is output from the light output unit 14 through c4, 6b2, and 6a in order are shown. In the present embodiment, light of wavelengths λ _7a and λ _7b is input from the light input unit 207. In this case, the lights of these wavelengths are multiplexed with low loss by the wavelength multiplexer 2 and output from the optical output unit 14.

Further, (d) of FIG.
The light input from the Mach-Zehnder interference type multiplexing means 6
The light transmission characteristics when the light is output from the light output unit 14 through c4, 6b2, and 6a in order are shown. In the present embodiment, light of wavelengths λ _8a and λ _8b is input from the light input unit 208. In this case, the light of these wavelengths is multiplexed by the wavelength multiplexer 2 with low loss and output from the optical output unit 14.

The wavelengths λ _1a , λ _1b ,... Λ
The specific values of _8b are the values shown in Table 1.

[0063]

[Table 1]

The present embodiment is configured as described above. The lights of the wavelengths λ _1a and λ _1b output from the pump light source 1 are multiplexed by the polarization combiner 3 and the light of the wavelength The light having the wavelengths λ _2a and λ _2b is similarly input by the polarization combiner 3 and input to the optical input unit 202 of the wavelength multiplexer 2, and the light having the wavelengths λ _7a and λ _7b is similarly input. The light is multiplexed by the polarization combiner 3 and is input to the optical input unit 207 of the wavelength multiplexer 2.
The lights of wavelengths λ _{8 a} and λ _{8 b} are multiplexed by the polarization combiner 3 and input to the optical input unit 208 of the wavelength multiplexer 2.

The lights of wavelengths λ ₃ , λ ₄ , λ ₅ , and λ ₆ are respectively supplied to the light input sections 203, 204, and 20 of the wavelength multiplexer 2.
5,206.

Then, by the function of the wavelength multiplexer 2, the pumping lights of the respective wavelengths λ _1a , λ _1b ,... Λ _8b are multiplexed by the wavelength multiplexer 2 with low loss. 2
Is output from the light output unit 14.

According to the present embodiment, four polarization combiners 3 are provided on the optical input side of the wavelength combiner 2, and the lights multiplexed by these polarization combiners 3 are respectively transmitted to the wavelength combiners 2. In the excitation light source device shown in FIG. 13, the configuration is such that the light is input to the corresponding light input units 201, 202, 207, and 208.
Since the total number of Mach-Zehnder interference type multiplexing means 6 required for one can be reduced to seven, and the number of connection stages of the Mach-Zehnder interference type multiplexing means 6 can be reduced from four to three steps, The problem of narrowing the wavelength bandwidth of the multiplexed light, which has been a problem in the wavelength multiplexer 2, can be solved, and the insertion loss of the wavelength multiplexer 2 can be significantly reduced as compared with the conventional example.

Since the multiplexing of the polarized waves by the respective polarization combiners 3 is performed with very low loss, the excitation light source device of the present embodiment is provided with the excitation light output from each excitation light source 1. An excellent pump light source device that can combine light with very low loss and output the light from the light output unit 14 can be provided.

Therefore, if the pump light source device of the present embodiment is applied to a Raman amplifying device, Raman amplification with good pumping efficiency and gain flatness can be realized.

Next, a description will be given of a second embodiment of the excitation light source device according to the present invention. The second embodiment is substantially similar to the first embodiment, and the second embodiment is different from the first embodiment in that
This means that the wavelength of the pump light output from the laser diode 107b is the wavelength λ _{7b ′} shown in FIG.

[0071]

[Table 2]

[0072] Light of this wavelength, as shown in the figure, the wavelength of the two distant low loss peak from the peak wavelength lambda _7a. Thus, the two wavelengths multiplexed by the polarization combiner 3 do not need to be adjacent peaks with low loss in the light transmission characteristics of the optical multiplexer / demultiplexer 2, and can be multiplexed by the polarization combiner 3. Any wavelength within the wavelength band may be used.

The second embodiment is configured as described above, and the second embodiment also operates in the same manner as in the first embodiment, so that the wavelengths λ _1a , λ _1b ,. _7a ,
The pump lights of λ _{7 b ′} , λ _8a , and λ _8b can be combined with low loss, and the same effect can be obtained.

FIG. 7 shows a main configuration of a third embodiment of the excitation light source device according to the present invention. The third embodiment is configured substantially in the same manner as the first embodiment, and the feature of the third embodiment different from the first embodiment is that, as shown in FIG. The wavelength multiplexer 2 is formed by connecting a plurality of Mach-Zehnder interference type multiplexing means 6 formed by optical fibers 15. In each of the optical fiber type Mach-Zehnder interference type multiplexing means 6, the directional coupler 12 is formed by a fusion type fiber coupler.

The optical fiber type Mach-Zehnder interference type multiplexing means 6 applied in the third embodiment is the same as the Mach-Zehnder interference type multiplexing means 6 of the optical waveguide circuit applied in the first embodiment. Since the third embodiment has a function, the third embodiment can also provide the same effect by the same operation as that of the first embodiment.

FIG. 9 shows the main configuration of a fourth embodiment of the excitation light source device according to the present invention. The fourth embodiment is substantially the same as the third embodiment, and the fourth embodiment is different from the third embodiment in that the Mach-Zehnder interference type multiplexing means 6 is different from the third embodiment. Instead, a wavelength multiplexer 2 is formed by connecting a plurality of fused fiber couplers 4 as shown in FIG. In addition,
The fused fiber coupler 4 is formed by an optical fiber 15.

Similarly to the Mach-Zehnder interference type multiplexing means 6, the fusion type fiber coupler 4 has two incident side transmission paths 5.
a and 5b function as an optical multiplexing means for multiplexing light having different wavelengths respectively incident thereon and transmitting the multiplexed light to one output-side optical transmission line 5c.
The fusion type fiber coupler 4 is applied as the optical multiplexing means.

The fourth embodiment is different from the first to the fourth embodiments.
Similarly to the connection configuration of the Mach-Zehnder interference type multiplexing means 6 in the third embodiment, a plurality of (four) fused fiber couplers 4 (4c1 to 4c4) are juxtaposed in the first stage. A second-stage fused fiber coupler 4 (4b) that further optically combines the optical outputs of the paired fused fiber couplers 4
1, 4b2), and a third-stage fused fiber coupler 4 (4a) for further optically multiplexing the optical outputs of these fused-type fiber couplers 4b1, 4b2. 4 is connected to a plurality of stages (three stages) such that the optical output of the optical fiber 4 is further optically multiplexed by the fused fiber coupler 4 at the subsequent stage.
Is formed.

The normalized power characteristic P of the light that enters from each of the incident-side transmission lines 5a and 5b and is output from the emission-side transmission line 5c of the fused fiber coupler 4 shown in FIG.
a and Pb are represented by the following equations, respectively.

Pa = 1−sin ² (2π · n · z / λ) (4)

Pb = sin ² (2π · n · z / λ) (5)

Here, z is the coupling length of the fused fiber coupler 4. Thus, the fused fiber coupler 4 is
Normalized power characteristics Pa of light incident from each of the incident-side transmission paths 5a and 5b and output from the emission-side transmission path 5c,
Since Pb can be represented by a sin function, wavelengths that can be combined with low loss appear periodically.

That is, by appropriately setting the coupling length and the like of the fused fiber coupler 4, each fused fiber coupler 4 has a unique period of the center wavelength of the multiplexed light that the fused fiber coupler 4 multiplexes. Therefore, by designing the fused fiber coupler 4 in the same manner as the design of the Mach-Zehnder interference type multiplexing means 6, the pump light source device of the fourth embodiment is configured.

The fourth embodiment is configured as described above, and the fourth embodiment can also achieve the same effects by performing substantially the same operations as the above embodiments.

The present invention is not limited to the above embodiment, but can adopt various embodiments. For example,
In each of the above embodiments, the number of the excitation light sources 1 is set to 12, but the number of the excitation light sources 1 is not particularly limited and may be appropriately set. For example, when the number of the excitation light sources 1 is 16, all the light input units 201 to 201 of the wavelength multiplexer 2 are used.
If the polarization combiner 3 is connected to 208, an excellent pumping light source device having the same effects as the above embodiments can be constructed using the same wavelength multiplexer 2 as the above embodiments. .

The output wavelength of the pump light source 1 is not particularly limited, but may be appropriately set. The wavelength multiplexer 2 may be appropriately designed, and the light transmission as shown in FIGS. By selecting a wavelength capable of multiplexing with low loss as the output wavelength of the pumping light source 1 based on the characteristics, it is possible to configure a pumping light source device having the same excellent effects as those of the above embodiments.

Further, in the first to third embodiments, the Mach-Zehnder interference type multiplexing means 6 is connected in three stages, and in the fourth embodiment, the fusion type fiber coupler 4 is connected in three stages and the wavelength multiplexing is performed. Although the wave combiner 2 is formed, the configuration of the wavelength multiplexer 2 is not particularly limited, and is appropriately set.

That is, by setting the number of connection stages of the Mach-Zehnder interference type multiplexing means 6 and the fusion type fiber coupler 4 to be as small as possible in accordance with the number of wavelengths multiplexed by the wavelength multiplexer 2, Insertion loss of the container 2 can be reduced. Further, instead of the Mach-Zehnder interference type multiplexing means 6 and the fused type fiber coupler 4, lights having different wavelengths respectively incident from two incident side transmission lines are multiplexed and transmitted to one emission side optical transmission line. Other optical multiplexing means can also be applied.

For example, in FIG. 11, optical multiplexing means for multiplexing light having different wavelengths respectively incident from two incident-side transmission lines and transmitting the multiplexed light to one emission-side optical transmission line is connected in two stages. The wavelength multiplexer 2 thus formed is schematically shown. Hereinafter, the optical multiplexing function of the optical multiplexing means will be briefly described with reference to FIG.

In the figure, reference numerals 401, 402 and 403 are assigned to the respective optical multiplexing means, and the central wavelengths of the multiplexed light multiplexed by these optical multiplexing means 401, 402 and 403 are respectively unique. It has a cycle. The inherent period of the optical multiplexing means provided in the (n-1) -th stage (here, n = 2 and the first-stage optical multiplexing means 401 and 402) is the optical multiplexing means provided in the second-stage. This is an integral multiple of the inherent period of the means 403.

Here, with respect to the optical multiplexing means 403, when the insertion loss of the light input from the port 305 and output from the port 307 is obtained, the characteristic line a in FIG. 12A and the characteristic line a in FIG. This is shown by the characteristic line a. That is,
In this case, in the optical multiplexing means 403, multiplexed light central wavelengths (center wavelengths of light that can be multiplexed with low loss) input from the cross port and multiplexed are λ _A , λ _B , λ _C , λ _D ,.
・ ・The center wavelength of the multiplexed light, which is input from the through port (port 306) of the optical multiplexing means 403 and is multiplexed, is not shown in the figure, but the wavelength between λ _A and λ _B , λ _C specific period of since the wavelength ... (see (a) of FIG. 6) optical multiplexing means 403 between the lambda _D is half of the period of [Delta] S.

The optical multiplexing means 401 has a port
Insertion of light input from port 301 and output from port 305
When the input loss is obtained, the input loss is shown by the characteristic line b in FIG.
In this case, the light is multiplexed by the optical multiplexing means 401.
The center wavelength of the multiplexed light is λ_A, Λ _C, ... on the other hand,
For the optical multiplexing means 401, input from the port 302
When the insertion loss of the light output from the port 305 is obtained,
As shown by the characteristic line b in FIG.
The center wavelength of the multiplexed light multiplexed by 401 is λ_B, Λ_D,
... That is, the unique circumference of the optical multiplexing means 401
The period is ΔS, which is twice the inherent period of the optical multiplexing means 403.
It has become.

As described above, by setting the period of the optical multiplexing means 401 and the optical multiplexing means 403 and connecting the optical multiplexing means 403 at the subsequent stage of the optical multiplexing means 401, the characteristic line a and the characteristic line b are both low. Only the wavelength of the insertion loss is port 3
07, light of wavelengths λ _A , λ _C ,... Among the light input from the port 301, as indicated by the characteristic line c in FIG. The light of wavelengths λ _B , λ _D ,... Among the light output with low loss and input from port 302 is output from port 307 with low loss.

Therefore, in the present invention, the wavelength multiplexer 2 multiplexes the light beams having different wavelengths, which are respectively input from the two incident-side transmission lines, and transmits the multiplexed light to one output-side optical transmission line. The means are connected in a plurality of stages, the multiplexed light center wavelengths multiplexed by the respective optical multiplexing means have their respective periods, and the multiplexing means has a specific period. By setting the cycle to be an integral multiple of the inherent cycle of the optical multiplexing means provided at the n-th stage, the same effects as those of the above embodiments can be obtained.

However, if the optical multiplexing means is composed of the Mach-Zehnder interference type multiplexing means 6 and the fused fiber coupler 4 as in each of the above-described embodiments, since the manufacturing techniques and functions thereof are well known, the wavelength It is easy to manufacture the multiplexer 2 and the like, and it is possible to reliably form an excitation light source device exhibiting the above-described excellent effects.

[0096]

According to the first aspect of the present invention, polarized lights having different polarization states and wavelengths are multiplexed by a polarization combiner, and the multiplexed light is transmitted from one or more optical input units of the wavelength multiplexer. Since the light is input to the wavelength multiplexer, the number of optical input units provided in the wavelength multiplexer can be reduced by the number of the polarization multiplexers, and the insertion loss of the wavelength multiplexer can be reduced. It is possible to combine pumping lights having different wavelengths and output a high output.

In particular, in the present invention, the wavelength multiplexer
In the second invention in which a plurality of optical multiplexing means for multiplexing lights having different wavelengths respectively incident from the input-side transmission paths and transmitting the multiplexed light to one output-side optical transmission path are connected in a plurality of stages, As described above, the number of optical input sections of the wavelength multiplexer can be reduced by the number of the polarization multiplexers, so that the number and the number of optical multiplexers forming the wavelength multiplexer can be reduced. Thus, the problem of narrowing the wavelength bandwidth of the multiplexed light, which has been a problem in a wavelength multiplexer having a large number of stages, can be suppressed, and the insertion loss of the wavelength multiplexer can be significantly reduced.

Therefore, according to the first and second aspects,
It is possible to provide a pumping light source device capable of multiplexing pumping lights having a large number of wavelengths and outputting a high output.
The Raman amplification efficiency of the aman amplification type optical amplifier can be improved.

Further, according to the third aspect, the center wavelengths of the multiplexed lights multiplexed by the respective optical multiplexing means have their own periods, and the (n-1) th stage (n is 2 or more) Since the natural cycle of the optical multiplexing means provided at (integer) is an integer multiple of the natural cycle of the optical multiplexing means provided at the n-th stage, the excitation light source is provided by the optical multiplexing means connected at a plurality of stages. Pump light from the light source can be multiplexed with low loss, and the pump light source device exhibiting the above-described excellent effects can be reliably formed.

Further, as in the fourth to seventh aspects, the optical multiplexing means may be a Mach-Zehnder interference type multiplexing means having two directional couplers, or may be a fusion type fiber coupler, so that A multiplexer can be easily manufactured, and an excitation light source device having the above effects can be reliably provided.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram showing a first embodiment of an excitation light source device according to the present invention.

FIG. 2 is an explanatory diagram showing a cross-sectional configuration of an optical waveguide circuit forming a wavelength multiplexer according to the embodiment.

FIG. 3 is a diagram illustrating an example of the configuration of the wavelength multiplexer 2 according to the embodiment.
5 is a graph showing transmission characteristics (loss) of light output from the optical disk.

FIG. 4 is a diagram illustrating an example of the configuration of the wavelength multiplexer 2 according to the embodiment.
5 is a graph showing transmission characteristics (loss) of light output from the optical disk.

FIG. 5 is an explanatory diagram showing a configuration of a wavelength multiplexer formed by connecting two stages of Mach-Zehnder interference type multiplexing means.

6A and 6B are graphs schematically showing light transmission characteristics of respective Mach-Zehnder interference type multiplexing means 6a and 6b forming the wavelength multiplexer 2 shown in FIG.
A graph (c) schematically showing the transmission characteristics of light input from the light output unit 1502 and output from the light output unit 14.
It is.

FIG. 7 is a main part configuration diagram showing a third embodiment of the excitation light source device according to the present invention.

FIG. 8 is a configuration diagram of an optical fiber type Mach-Zehnder interference type multiplexing means constituting the third embodiment.

FIG. 9 is a main part configuration diagram showing a fourth embodiment of the excitation light source device according to the present invention.

FIG. 10 is a configuration diagram of an optical fiber-type fused fiber coupler constituting the fourth embodiment.

FIG. 11 is an explanatory diagram showing an example of a wavelength multiplexer formed by connecting optical multiplexing means having two incident-side transmission lines and one emission-side transmission line in two stages.

12 schematically shows light transmission characteristics of an optical multiplexing unit included in the wavelength multiplexer shown in FIG. 11, and transmission characteristics of light input from ports 301 and 302 and output from port 307. FIG. It is a graph.

FIG. 13 is an explanatory diagram showing a configuration example of a conventional excitation light source device.

FIG. 14 is an explanatory diagram of a basic configuration of a Mach-Zehnder interference type multiplexing unit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Excitation light source 2 Wavelength multiplexer 3 Polarization synthesizer 4 Fused fiber coupler 5a, 5b Incident side transmission line 5c Exit side transmission line 6 Mach-Zehnder interference type multiplexing means 8 Excitation light output fiber 9 Optical input fiber 10 Core circuit 12 Directional coupler 14 Optical output section 22 Grating (fiber grating) 101a-108b Laser diode 201-208 Optical input section (input port)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Kawashima 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd. F-term (reference) 2H047 KA03 KA12 KB04 LA11 LA18 MA05 TA05 TA31 5F072 AB09 AK06 JJ04 KK30 PP07 QQ07 RR01 YY17 5K002 BA01 BA02 BA05 DA02

Claims (7)

[Claims] 1. A wavelength multiplexer for multiplexing lights of a plurality of wavelengths different from each other, and two polarized lights having different polarization states from each other are supplied to at least one optical input unit of the wavelength multiplexer. The optical output section of the polarization combiner to be multiplexed is connected, and two pump light sources for outputting polarized lights having different polarization states and wavelengths are connected to the optical input section of the polarization combiner. An excitation light source device characterized by the above-mentioned. 2. A wavelength multiplexer includes a first-stage optical multiplexing means for multiplexing light beams having different wavelengths respectively incident from two incident-side transmission lines and transmitting the multiplexed light to one emission-side optical transmission line. Have multiple,
A second-stage optical multiplexing means for further multiplexing the optical outputs of the pair of optical multiplexing means of the first stage is connected, and the optical outputs of the pair of optical multiplexing means of the preceding stage are further multiplexed by the optical multiplexing means of the subsequent stage. 2. The pumping light source device according to claim 1, wherein the optical multiplexing means is formed by connecting a plurality of optical multiplexing means so as to wave. 3. The multiplexed light center wavelengths multiplexed by the respective optical multiplexing means have their own periods, and (n
-1) The characteristic period of the optical multiplexing means provided at the stage (n is an integer of 2 or more) is an integral multiple of the characteristic period of the optical multiplexing device provided at the n-th stage. Claim 2
The excitation light source device according to claim 1. 4. The pump light source device according to claim 2, wherein the optical multiplexing means is a Mach-Zehnder interference type multiplexing means having two directional couplers. 5. An excitation light source device according to claim 4, wherein said directional coupler is a fused fiber coupler. 6. The pump light source device according to claim 4, wherein the Mach-Zehnder interference type multiplexing means is formed by an optical waveguide circuit. 7. The pumping light source device according to claim 2, wherein the optical multiplexing means is a fused fiber coupler.