JPH04127133A - Selective converting method for wavelength multiplex light - Google Patents

Abstract

PURPOSE:To convert one wavelength to a different wavelength selectively and outputs it by setting the input light level of (n) kinds of wavelength which are multiplexed within in-use wavelength band width less than a wavelength difference between two adjacent wavelengths having minimum values above operation sensitivity to the input light level of a light wavelength converting element. CONSTITUTION:Light with (n) kinds of wavelength which are multiplexed within the in-use wavelength band width a little smaller than the wavelength difference between two adjacent wavelengths having the minimum values is inputted from an optical input part. Then the light level is so that only one of the (n) kinds of wavelengths is close to the wavelength which is minimum in operation sensitivity to the input light level of the light wavelength converting element 6 and the input light level is above the operation sensitivity to the input light level of the light wavelength converting element 6. Consequently, one wavelength in the light of (n) kinds of multiplexed wavelengths inputted from the light input part 4 is converted selectively into a difference wavelength, which is outputted from an optical output part 5.

Description

[Detailed Description of the Invention] [Summary] Regarding a method for selectively converting wavelength-multiplexed light, the present invention provides a method for selectively converting wavelength-multiplexed light with a simple configuration by performing wavelength conversion processing without converting an optical signal into an electrical signal. Is it intended to be gain domain or wavelength domain? 11 regions, a saturable absorption region, and a wavelength control region, it converts the wavelength of input light into a wavelength different from the wavelength of the input light and outputs it, and the operating sensitivity to the input light level is periodic on the wavelength axis. In an optical wavelength conversion element that has the characteristic of changing to a maximum value and a minimum value alternately, the wavelength is multiplexed from the optical input section within a used wavelength bandwidth that is smaller than the wavelength difference between two adjacent wavelengths having a minimum value. When inputting light of n different wavelengths, only one wavelength is near the wavelength at which the operating sensitivity of the optical wavelength conversion element to the input light level takes a minimum value, and the input light level of that wavelength is the same as that of the optical wavelength conversion element. By setting the operating sensitivity to the input light level or higher, it selectively converts one wavelength from among the input multiplexed wavelengths of light into a different wavelength and outputs it. do.

[Field of Industrial Application] The present invention relates to a method for selectively converting wavelength-multiplexed light, and in particular, the present invention relates to a method for selectively converting wavelength-multiplexed light, and in particular, the present invention relates to a method for selectively converting wavelength-multiplexed light. The present invention relates to a method for selectively converting wavelength-multiplexed light to convert wavelengths of light.

With the development of optical communication network technology, various studies are being conducted on optical signal exchange methods such as optical switching and optical subscriber systems.

Among them, one of the features of optical fiber transmission system, broadband property, that is, the ability to handle optical signals of multiple frequencies or multiple wavelengths at the same time, can be utilized for example to connect and exchange subscribers and terminals. A wavelength multiplexing type optical communication system has been proposed, which allocates optical wavelengths according to the destination, converts the wavelength of the optical signal according to the destination, and transmits the signal.

In such an optical wavelength division multiplexing communication system, an optical wavelength conversion element is used as an optical wavelength conversion device having characteristics that allow the wavelength of an optical signal to be freely converted, and an optical wavelength conversion device using such an optical wavelength conversion element is used. For this reason, optical wavelength conversion elements that convert the wavelength of an input optical signal and output it by applying semiconductor laser technology have been proposed and researched.

When applying such optical wavelength conversion processing to wavelength-multiplexed optical signals, it is necessary to In order to be able to perform wavelength conversion, the optical wavelength conversion element is required to have a characteristic of selectively responding to wavelength.

This Prior Art] FIGS. 8(a) to (C) and FIGS. 9(a) and (b) show a conventional optical wavelength conversion method.

FIGS. 8(a) to 8(C) show examples of selective conversion of optical wavelengths by optical/electrical conversion and electric/optical conversion.

In FIG. 8(a), light having n types of wavelengths λ1 to λ9 multiplexed on the wavelength axis is input to a wavelength filter 61 that selects a transmission wavelength to be variable or fixed.

The wavelength filter 61 selectively transmits only the light λ of a desired wavelength and inputs it to the optical/electrical conversion circuit 62 . The optical/electrical conversion circuit 62 once converts all optical data of wavelength λ into electrical signals, and inputs the electrical signals to the electrical/optical conversion circuit 63 .

The electrical/optical conversion circuit 63 outputs light of a wavelength λ different from the wavelength λ in response to this electrical signal. This achieves the function of selectively converting optical wavelengths.

In FIG. 8(b), a demultiplexer 64 is used in place of the wavelength filter 61, and the light of a desired wavelength λ is fixedly separated, and the light is inputted to an optical/electrical conversion circuit 62 to generate an electrical signal. Convert to This electrical signal causes the electrical/optical conversion circuit 63 to
By generating light with a wavelength λ4 through the wavelength λ4, the function of selectively converting the optical wavelength is realized.

As the electrical/optical conversion circuit 63 in the examples shown in FIGS. 8(a) and 8(b), an optical modulator that inputs light of wavelength λj from the outside and modulates the light with an electrical signal may be used. can.

In FIG. 8(C), light with a wavelength λj (DC light) is modulated according to an electrical signal input to generate light with a wavelength λ (modulated light).
has been shown to occur.

In addition, with the development of semiconductor laser technology in recent years,
Wavelength conversion semiconductor lasers have been proposed and researched, which can output light at a wavelength different from the wavelength of input light by controlling current.

FIGS. 9(a) and 9(b) illustrate a case in which selective conversion of optical wavelength is performed by an optical wavelength conversion element using a wavelength conversion semiconductor laser.

In Fig. 9(a) and b), Fig. 8(a) and b) respectively
By replacing the optical/electrical conversion circuit 62 and the electrical/optical conversion circuit 63 in a) and (b) with an optical wavelength conversion element 72 and coupling it with a variable or fixed wavelength filter 61 or a demultiplexer 64, the optical This shows a configuration for selectively converting wavelengths.

[Problem to be solved by the invention] Figures 8 (a) to (C) and Figures 9 (a) and (b)
In the conventional method shown in , it is necessary to place a wavelength filter or a demultiplexer for selecting the wavelength to be converted from wavelength-multiplexed light before the wavelength converter.

Furthermore, in the configurations shown in FIGS. 8(a) to (C), the wavelength conversion section consisting of an optical/electrical conversion circuit and an electrical/optical conversion circuit corresponds to the output port of each wavelength filter or demultiplexer. Is required.

Therefore, in order to realize the selective conversion function of wavelength multiplexed light, a combination of a wavelength filter or a demultiplexer and a wavelength converter is always used.

Therefore, for example, in order to realize the function of multiplexing light of many wavelengths on the wavelength axis and selectively converting the wavelength of light of each wavelength, it is necessary to multiplex the light of many wavelengths on the wavelength axis and convert the wavelength of each wavelength selectively. In the configuration, since it is necessary to provide a number of optical/electrical conversion circuits and electrical/optical conversion circuits corresponding to the number of wavelengths, there is a problem that the hardware becomes large-scale when multichannel is used.

Furthermore, even in the configurations shown in FIGS. 9(a) and 9(b), the wavelength filter or demultiplexer and the optical wavelength conversion element must be combined, which not only requires mutual coupling and control, but also requires a large number of components. When handling wavelengths, a configuration using a demultiplexer requires a demultiplexer with high wavelength separation characteristics, resulting in an unavoidable complication in the configuration.

The present invention aims to solve the problems of the prior art, and is capable of performing wavelength conversion processing without converting an optical signal into an electrical signal, and without requiring a wavelength filter or a demultiplexer. It is an object of the present invention to provide a method for selectively converting wavelength-multiplexed light, which can perform selective wavelength conversion of wavelength-multiplexed light with a relatively simple configuration.

[Means for Solving the Problems] The method for selectively converting wavelength multiplexed light of the present invention includes a gain region or a wavelength control region 1 that is a gain region for amplifying input light or a wavelength control region for controlling an oscillation wavelength; It is equipped with a saturable absorption region 2 whose absorption becomes zero when it absorbs and becomes saturated, and a wavelength control region 3 which controls the oscillation wavelength. In addition, the operating sensitivity to the input light level from the optical input section 4 changes periodically on the wavelength axis and alternately produces maximum and minimum values. nll1lf is multiplexed from the optical input section 4 to the optical wavelength conversion element 6 having the characteristic within the used wavelength bandwidth that is slightly smaller than the wavelength difference between two adjacent wavelengths having this minimum value.
Input light with a wavelength of .

And only one of these nil wavelengths is
The setting is such that the operating sensitivity of the optical wavelength conversion element 6 to the input light level is near a wavelength at which the minimum value is reached, and the input light level of that wavelength is greater than or equal to the operating sensitivity of the optical wavelength conversion element 6 to the input light level. do.

As a result, one wavelength is selectively converted into a different wavelength from among the NIL multiplexed wavelength lights inputted from the optical input section 4 and outputted from the optical output section 5.

Further, the present invention provides an optical wavelength conversion element 6 which includes an active layer 10 for generating optical energy, which is composed of a first gain region 7, a second gain region 8, and a saturable absorption region 9, and an active layer 10 for generating optical energy. A light guide layer 15 for guiding light forming a phase shift region 11 to be shifted is provided, and a diffraction grating 14 forming a DBR region 12 for resonating light is provided in an extension of this light guide layer 15. Schiff) Wavelength system that controls the oscillation wavelength in the 91 region 11 and the DBR region 12? il fil region 13, and the operating sensitivity to the input light level changes periodically on the wavelength axis due to the wavelength dependence of the reflectance at the end face and the diffraction grating 14, and alternately takes a maximum value and a minimum value. A wavelength conversion semiconductor laser 16 is provided which has characteristics that produce the following.

Then, from the optical input section 4, light of n types of wavelengths multiplexed within the used wavelength bandwidth that is slightly smaller than the wavelength difference between two adjacent wavelengths having this minimum value is input, and at the same time, light of n types of wavelengths is input. Only one of the wavelengths is near the wavelength where the operating sensitivity to the input light level of this wavelength conversion semiconductor laser 16 takes a minimum value, and the input light level of that wavelength is close to the input light level of this wavelength conversion semiconductor laser 16. Set it so that it is higher than the operating sensitivity.

As a result, one wavelength is selectively converted into a different wavelength from among the n types of multiplexed wavelength light inputted from the optical input section 4, and the converted wavelength is outputted from the optical output section 5.

Further, the present invention provides at least two wavelength conversion elements as the optical wavelength conversion element 6.
It has two or more electrodes in series, one of which is used as a saturable absorption region 18, the rest is used as a gain region or wavelength control region 17, and an active layer 19 for generating optical energy. , a diffraction grating 20 provided in or adjacent to this active layer 19, and the operational sensitivity to the input light level is on the wavelength axis due to the dependence of the gain in this active layer 19 on the diffraction wavelength in the diffraction grating 20. A multi-electrode DFB wavelength conversion semiconductor laser 21 is provided which has a characteristic of changing periodically at the top and alternately producing a maximum value and a minimum value.

Then, from the optical input section 4, light of n types of wavelengths multiplexed within the used wavelength bandwidth that is slightly smaller than the wavelength difference between two adjacent wavelengths having this minimum value is input, and at the same time, light of n types of wavelengths is input. Only one of the wavelengths is near the wavelength at which the operating sensitivity of the multi-electrode DFB wavelength converting semiconductor laser 21 to the input light level takes a minimum value, and the input light level of that wavelength is the same as that of the multi-electrode DFB wavelength converting semiconductor laser 21. 21
Set so that the operating sensitivity for the input light level is greater than or equal to the input light level.

As a result, one wavelength is selectively converted into a different wavelength from among the n[rll multiplexed wavelength lights inputted from the optical input section 4 and outputted from the optical output section 5.

〔Example〕

FIG. 2 shows an example of the configuration of the optical wavelength conversion element.

The optical wavelength conversion element 6 includes a gain region or wavelength control region 1, a saturable absorption region 2, a wavelength selection region 3, and an optical input section 4.
and a light output section 5.

Here, the gain region is a portion having a function of amplifying input light. The saturable absorption region is a part that absorbs input light or light generated inside the light conversion element, but the absorption coefficient decreases as the internal light level increases, and above a certain light level, it becomes saturated and absorption becomes zero. Become. Wavelength control II'6M
For example, by changing the current value supplied to the optical wavelength conversion element to change the refractive index and control the resonance conditions,
This is the part that controls the oscillation wavelength. The optical input part is a part that inputs an optical signal from the outside, and the optical output part is a part that outputs the oscillation light of the optical wavelength conversion element. In this case, the method of coupling the optical wavelength conversion element and the signal light or output light is , is appropriately selected depending on the structure and shape of the optical wavelength conversion element.

FIGS. 3(a) and 3(b) show the characteristics of the optical wavelength conversion element, where (a) shows its function and β) shows the optical input/output characteristics.

That is, as shown in FIG. 3(a), the optical wavelength conversion element 6
When light of a certain wavelength λ8i is input, in response to that signal, light of a wavelength λi different from λi7 is input. Outputs ut light.

Since the optical wavelength conversion element has a gain region and a saturable absorption region as described above, it exhibits a threshold characteristic as shown in FIG. 3(C) in terms of optical input/output characteristics.

That is, the input level of light with wavelength λi is a certain value P(λ
, 7), the optical output increases rapidly, and the output wavelength is different from λ87. , is.

At this time, the threshold value Pub(λ
1. ．． ) represents the operating sensitivity of the optical wavelength conversion element 6 to the input light level. Further, the output light wavelength is determined by the wavelength dependence of the gain in the gain region and the feedbank of the gain to light of a specific wavelength controlled in the wavelength region.

Therefore, if the structure is such that the gain in this gain region and the feedback of the gain to light of a specific wavelength are periodically distributed with respect to the wavelength, for example, the dependence of this operating sensitivity on the input light wavelength will be However, it becomes periodic,
Moreover, it has a minimum value at a specific wavelength where the gain and gain feedback in the gain region are large.

Examples of such optical wavelength conversion elements include wavelength conversion semiconductor lasers and multi-electrode DFB wavelength conversion semiconductor lasers.

FIG. 4 shows an example of the configuration of a wavelength conversion semiconductor laser.

In FIG. 4, 16 indicates a wavelength conversion semiconductor laser,
7 is a first gain region, 8 is a second gain region, and 9 is a saturable absorption region. Further, 11 is a phase shift region, and 12 is a DBR (distributed Bragg reflection) region, which form a wavelength control region 13. 10 is an active layer, I4 is a diffraction grating, and 15 is a light guide layer.

The active layer 10 is a portion that generates optical energy using electrical energy, and the current injection region below the two electrodes becomes a gain region, and the middle portion without an electrode becomes a saturable absorption region.

The light guide layer 15 is a portion that guides light generated in the active layer 10, and forms a phase shift region 11 that shifts the phase of the generated light. A diffraction grating 1 is provided on one side of the light guide layer 15.
4 is provided to form a DBR region in which resonance occurs due to the interaction between the light energy transmitted from the phase shift 6M region 11 and the diffraction grating 14.

In the wavelength conversion semiconductor laser shown in FIG. 4, if the injection current conditions to the two gain regions 7 and 8 are appropriately set, when light of wavelength λ and 7 is injected from the outside, the optical input p
There exists a threshold characteristic as shown in Fig. 3(b) between in and optical output P out, and when the optical input level of wavelength λ and w exceeds a certain value Pub, laser oscillation suddenly occurs. Start with a large light output P. 5 is obtained. The output light wavelength at this time is a wavelength λ different from the input light wavelength λ8°. . , has been converted to .

FIG. 5 shows an example of the operating sensitivity of a wavelength conversion semiconductor laser, and shows an example of the measurement results of the operating sensitivity to the input light level during wavelength conversion operation, that is, the dependence of the threshold value P on the input light wavelength. It is.

As shown in FIG. 5, the operating sensitivity to the input light level, that is, the threshold value P, changes periodically with respect to the input light level and takes a minimum value at a certain wavelength.

FIG. 6 shows a configuration example of a multi-electrode DFB (distributed feedback) wavelength conversion semiconductor laser, in which 17 is a gain region or wavelength control region, 18 is a saturable absorption region, and 19 is a multi-electrode DFB (distributed feedback) wavelength conversion semiconductor laser 21. The active layer 20 is a diffraction grating.

Since the multi-electrode DFB wavelength conversion semiconductor laser shown in FIG. 6 also has the diffraction grating 20 close to the active layer 19,
The operating sensitivity to input light is expected to take a maximum and minimum at a specific wavelength, reflecting the internal refractive index determined by the period of the diffraction grating and the carrier concentration in the active layer.

FIG. 7 shows the operating conditions of the optical wavelength conversion element and the setting of the input light level.

It is assumed that the operating sensitivity of the optical wavelength conversion element to the input light level changes periodically with respect to the input light wavelength, and takes maximum and minimum values.

At this time, assuming that there are n types of wavelengths used in the optical wavelength multiplexing system, the mutual spacing between two adjacent wavelengths at which the operating sensitivity of the optical wavelength conversion element takes a minimum value is determined as A as shown in FIG.
, the n types of light wavelengths are slightly smaller than this Δ (A
-ΔΔ) at appropriate intervals. It is assumed that the input light level of each wavelength is uniform.

At this time, by appropriately adjusting the operating conditions and input light level of the optical wavelength conversion element, a desired wavelength λ of the n types of light spread within the range of (Δ−ΔΔ) can be obtained.
, Takeka, the optical wavelength conversion element is located very close to the wavelength at which the operating sensitivity to the input light level takes a minimum value, and the input light level is at the required operating level, that is, the operating threshold P, only for that wavelength. It is possible to exceed the

In state 2, the optical wavelength conversion element selectively responds only to a signal of wavelength λ, converts this signal to a wavelength λ different from the wavelength λ of the input light, and outputs the signal. As a result, among the n wavelengths of light input to the optical wavelength conversion element,
Only the light of wavelength λ is selectively converted to wavelength λ4 and output.

〔Example〕

FIGS. 1(a) and 1(b) show an embodiment of the present invention, in which an optical wavelength conversion switch is configured. In the figures, 6-1. -, 6-i, -, and 6-n are optical wavelength conversion elements, which perform wavelength conversion on light of a desired specific wavelength of the wavelength-multiplexed optical signal.

FIG. 1(a) shows a case where an IXn optical star coupler 51 is used. The optical star coupler 5 divides the wavelength-multiplexed optical signal input from the optical highway into n different paths with equal power.

In FIG. 1(a), when a wavelength multiplexed optical signal in which n types of wavelengths are multiplexed is input from the optical highway, it is branched into n different paths by the lXn star coupler 51 and outputted to the optical wavelength conversion element. 6-1.・-26-i, -, 6-n
Enter each. Optical wavelength conversion element 6-1. -, 6
-i+-, 6-n selects only light with a desired wavelength set in advance in each element from n types of wavelengths, converts the wavelength, and connects to other optical highways not shown. do.

1 et al.), in place of the optical star coupler 51 of IXn,
n 1×2 optical couplers 52-1. -.-152-n are connected in cascade and used.

In this case, n 1×2 optical couplers 52-1 . ---. 52-n, the wavelength multiplexed lights of λ, to λ7 are input, and one of the outputs of the wavelength multiplexed lights of λ1 to λゎ is inputted to n optical wavelength conversion elements 6-1. -, 6-n
In each optical wavelength conversion element, only one desired wavelength is selected from among the n types of wavelengths, and the selected wavelength is converted and connected to other optical highways.

In the above embodiment, each optical wavelength conversion element 61, -,
6-i, ---, and 6-n selectively convert one wavelength fixedly set in each element from among n wavelengths of light. By controlling the injection current and temperature of the laser, the operating sensitivity distribution for the input light wavelength can be controlled externally, and the wavelength at which the operating sensitivity takes a minimum value can be selectively changed and tuned. , a configuration may be adopted in which wavelength conversion is performed by freely selecting light whose wavelength is to be converted from among n types of wavelengths.

In this case, the output wavelength λ as a result of wavelength conversion. 5t
is the optical wavelength conversion element 6-1.・-・, 6-1+, 6-n
One fixed wavelength may be used for each of the wavelengths.

〔Effect of the invention〕

As explained above, according to the present invention, wavelength conversion processing is performed without converting an optical signal into an electrical signal from among light of a plurality of wavelengths multiplexed on the wavelength axis, and wavelength filters and demultiplexers are used. Since the selective wavelength conversion method can be realized with a simple configuration that does not use a waveguide, it will greatly contribute to the realization of an optical wavelength division multiplexing transmission network that takes advantage of the multiplicity of wavelengths.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are diagrams showing an embodiment of the present invention,
Figure 2 is a diagram showing an example of the configuration of an optical wavelength conversion element, and Figure 3 (a
), (b) is a diagram showing the characteristics of the optical wavelength conversion element, FIG. 4 is a diagram showing a configuration example of a wavelength conversion semiconductor laser, FIG. 5 is a diagram illustrating the operating sensitivity of the wavelength conversion semiconductor laser, and FIG. 6 is a diagram showing a configuration example of a multi-electrode DFB wavelength conversion semiconductor laser,
Figure 7 is a diagram showing the operating conditions of the optical wavelength conversion element and the setting of the input light level, Figures 8 (a) to (C) and Figure 2 (
Figures a) and (b) are diagrams showing a conventional optical wavelength conversion method. 1 is a gain region or a wavelength control region, 2 is a saturable absorption region, 3 is a wavelength control region, 4 is an optical input section, 5 is an optical output section, 6
is an optical wavelength conversion element, 7 is a first gain region, 8 is a second gain region, 9 is a saturable absorption region, 10 is an active layer, 11 is a phase shift) 6M region, 12 is a D B RfiI region, 13 1 is a wavelength control region, 14 is a diffraction grating, 15 is a light guide layer, 1
6 is a wavelength conversion semiconductor laser, 17 is a gain region or wavelength control region, 18 is a saturable absorption region, 19 is an active layer, 20
is a diffraction grating, and 21 is a multi-electrode DFB wavelength conversion semiconductor laser.

Claims (3)

[Claims] (1) Gain region or wavelength control region that is a gain region that amplifies input light or a wavelength control region that controls oscillation wavelength (
1), a saturable absorption region (2) whose absorption becomes zero when it absorbs light and becomes saturated, and a wavelength control region (3) which controls the oscillation wavelength, and receives input from the optical input section (4). The wavelength of the light is converted to a wavelength different from the wavelength of the input light and the light output section (5
), and an optical wavelength conversion element (6) having a characteristic that the operating sensitivity to the input light level from the optical input section (4) changes periodically on the wavelength axis and alternately produces maximum and minimum values. ), inputting from the optical input section (4) light of n types of wavelengths multiplexed within a used wavelength bandwidth that is slightly smaller than the wavelength difference between two adjacent wavelengths having the minimum value, and Only one wavelength out of n types of wavelengths is detected by the optical wavelength conversion element (6
) is near a wavelength where the operating sensitivity to the input light level of the optical wavelength conversion element (6) takes a minimum value, and the input light level at that wavelength is set so that it is equal to or higher than the operating sensitivity to the input light level of the optical wavelength conversion element (6). Accordingly, one wavelength is selectively converted into a different wavelength from among the n types of multiplexed wavelength light inputted from the optical input section (4) and outputted from the optical output section (5). Features selective conversion method for wavelength multiplexed light. (2) The optical wavelength conversion element (6) includes a first gain region (7), a second gain region (8), and a saturable absorption region (9).
) for generating light energy consisting of an active layer (1
0) and a phase shift region (11) that shifts the phase of light.
); and a light guide layer (15) for guiding light.
D that performs a light resonance effect on the extended portion of the light guide layer (15);
The phase shift region (11) and the DBR region (12) constitute a wavelength control region (13) that controls the oscillation wavelength by providing a diffraction grating (14) forming the BR region (12), and controlling the operation with respect to the input light level. A wavelength-converting semiconductor laser (with a sensitivity that changes periodically on the wavelength axis due to the wavelength dependence of the reflectance at the end face and the diffraction grating (14) and alternately produces maximum and minimum values) 16), and inputs light of n types of wavelengths multiplexed within a used wavelength bandwidth that is slightly smaller than the wavelength difference between two adjacent wavelengths having the minimum value from the optical input section (4). In addition, only one wavelength among the n types of wavelengths is converted into the wavelength conversion semiconductor laser (
The operating sensitivity to the input light level of the wavelength conversion semiconductor laser (16) is near the wavelength where it takes a minimum value, and the input light level of the wavelength conversion semiconductor laser (16) is set to be equal to or higher than the operating sensitivity to the input light level of the wavelength conversion semiconductor laser (16). By doing so, selectively converting one wavelength into a different wavelength from among the n types of multiplexed wavelength light inputted from the optical input section (4) and outputting it from the optical output section (5). 2. The method for selectively converting wavelength-multiplexed light according to claim 1. (3) As the optical wavelength conversion element (6), at least two
It has three or more electrodes in series, at least one of which is used as a saturable absorption region (18), and the rest is used as a gain region or wavelength control region (17), and an active layer for generating optical energy. (19) and a diffraction grating (2) provided in or adjacent to the active layer (19).
0), the operating sensitivity to the input light level varies periodically on the wavelength axis and alternately reaches maximum due to the dependence of the gain in the active layer (19) on the diffraction wavelength in the diffraction grating (20). It has a multi-electrode DFB wavelength conversion semiconductor laser (21) which has the characteristic of producing a maximum value and a minimum value, and from the optical input section (4), a wavelength difference slightly smaller than the wavelength difference between two adjacent wavelengths having the minimum value is used. While inputting light of n types of wavelengths multiplexed within the wavelength bandwidth, only one wavelength among the n types of wavelengths increases the operational sensitivity to the input light level of the multi-electrode DFB wavelength conversion semiconductor laser (21). is in the vicinity of a wavelength that takes a minimum value, and the input light level of that wavelength is the multi-electrode DFB wavelength conversion semiconductor laser (21).
By setting the operating sensitivity to the input light level or higher, one wavelength is selectively converted into a different wavelength from among the n types of multiplexed wavelength light inputted from the optical input section (4). 2. The method of selectively converting wavelength-multiplexed light according to claim 1, wherein the wavelength-multiplexed light is converted into a wavelength-multiplexed light and outputted from the light output section (5).