JPH07154019A - Wavelength conversion system - Google Patents

Abstract

PURPOSE:To convert the wavelength of an input signal light into a desired wavelength determined by the oscillation wavelength of a variable wavelength semiconductor laser by disposing a single mode variable wavelength semiconductor laser on the signal light input side. CONSTITUTION:An input signal light 10 is coupled with a variable wavelength semiconductor laser 1 through an input fiber 3. The oscillation light of the laser 1 is subjected to intensity modulation by the input signal light and the wavelength thereof is converted. The oscillation light of the laser 1 is controlled by injecting a current into a control current wire 7 for varying the oscillation wavelength of the laser. An input signal component 11 delivered from the laser 1 is reflected on a diffraction grating 20 formed on an optical wavelength filter 2 toward an optical output section 30 thence taken out by means of an output optical fiber 4. The wavelength converted light is reflected on a diffraction grating 21-24 having a period being set depending on the wavelength toward each optical output section 31-34 thence taken out by means of an output optical fiber 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength conversion system capable of converting an input light wavelength to another wavelength and changing the output position of the converted light according to the converted light wavelength. The system according to the present invention is used in fields such as optical switching and optical interconnection.

[0002]

2. Description of the Related Art In optical conversion systems and optical transmission systems, it is necessary to superimpose a signal superposed on a signal light of a certain wavelength on a light of another wavelength. For example, as shown in FIG. 4, when a specific wavelength (eg, λ ₁ ) is assigned to a person (terminal) who wants to obtain certain information, it is superimposed on a carrier wave of the wavelength (eg, λ ₀ ). By superimposing the original signal on the light of the specific wavelength (for example, λ ₁ ), a person (terminal) who wants to obtain information can obtain the signal. In addition, the original signal light is made to exist even after wavelength conversion, and by transmitting the original signal light to the main line, the same procedure is applied to other terminals to which other wavelengths (eg, λ ₂ ) are allocated in the same manner. A system that can obtain information can be constructed.

In the conventional wavelength division multiplexing transmission system and optical switching system, there is a system for outputting signal light sent by a single mode optical fiber to an optical output position corresponding to the wavelength by using an optical filter. Was.
Further, as shown in FIG. 5, there is a system in which an optical signal is once converted into an electric signal by a light receiver, the signal is superimposed on a bias current of a semiconductor laser or the like, and then converted into an optical signal again. However, in such a system, its operation speed is determined by an electric circuit, and high speed operation (> 10 GHz) is difficult. Further, this system has a drawback that all the original signal light is absorbed by the photodetector and disappears. A system that converts the wavelength of the input signal light without using an electric circuit, converts it to a converted light of another wavelength, and then changes the optical output position according to the wavelength of the converted light. There was no example that realized a system that can take out the system as it is from the system again.

[0004]

As described above, the wavelength of the optical signal is converted into another wavelength without converting the optical signal into the electric signal, and the converted signal light is output according to the wavelength of the converted light. It has been desired to realize a wavelength conversion system that can change the position of the wavelength.

Therefore, an object of the present invention is to convert the wavelength of an optical signal into another wavelength without converting the optical signal into an electrical signal, and further change the output position of the converted signal light according to the wavelength of the converted light. It is to provide a wavelength conversion system capable of performing the above.

[0006]

In order to solve the above problems, in a wavelength conversion system according to the present invention, a single mode wavelength tunable semiconductor laser (wavelength conversion element) is used to convert the wavelength of signal light. It is arranged on the input side and converts the wavelength of the input signal light into a desired wavelength determined by the oscillation wavelength of the wavelength tunable semiconductor laser. Then, in the subsequent stage, a wavelength filter whose optical output position changes depending on the wavelength is arranged, and a system for changing the output position of the signal light converted by this wavelength filter was constructed. The single-mode wavelength conversion semiconductor laser arranged in the preceding stage can set the oscillation wavelength to an arbitrary wavelength by an external control current. In order to change the optical output position according to the wavelength of the converted signal light,
An optical wavelength filter whose destination changes depending on the wavelength of the input signal light was installed after the single mode wavelength tunable semiconductor laser.

[0007]

As described above, by using the wavelength conversion system according to the present invention, the wavelength of the input signal light is converted to another arbitrary wavelength, and the output port corresponding to the wavelength of the converted light which is changed by the control current is output. A wavelength conversion system that can extract converted signal light can be constructed. Further, the input signal light component can also be taken out from a predetermined output port without any change. A conceptual diagram of this system is shown in FIG. With this system, the signal component of the signal light 10 input to the optical fiber 3 for inputting the signal light is superposed on the wavelength-converted light having different wavelengths, and the optical fiber group 5 for outputting the wavelength-converted light according to the wavelength is output. Is output (converted light 12). In addition, the input signal light is extracted from the input signal light output optical fiber 4 without any change,
It will be sent to the next system. Reference numeral 7 in the figure indicates a current injection wire for controlling the converted light wavelength.

In the wavelength conversion using the wavelength tunable semiconductor laser according to the present invention, the saturation phenomenon of the laser oscillation mode gain by the input signal light is used in principle. That is, when light is externally injected into the oscillating semiconductor laser, stimulated emission of the input light occurs, and the amplification gain for the light in the laser resonator saturates and decreases. Therefore, the gain of the laser with respect to the oscillation light is also reduced, and the intensity of the oscillation light is reduced. When the input light intensity is intensity-modulated by a certain signal, the laser oscillation light intensity is modulated in accordance with the intensity change. At this time, since the wavelength of the input signal light and the wavelength of the laser oscillation light are different, wavelength conversion is achieved. Further, in the wavelength conversion method, since the principle of wavelength conversion is based on the oscillation mode gain modulation by the input light,
The wavelength-converted signal is the inverse of the input signal. Also, by making the laser wavelength tunable,
The converted light wavelength can be arbitrarily changed.

[0009]

Embodiments of the present invention will now be described in detail with reference to the drawings.

(Embodiment 1) FIG. 2 shows a first embodiment of the present invention. The wavelength conversion system 100 includes a wavelength tunable semiconductor laser 1 as a wavelength conversion element installed on the signal light input side and an optical wavelength filter 2 whose optical output position changes depending on the wavelength of the input signal light. 1 and the optical wavelength filter 2 are optically connected by an optical fiber 6. Here, a distributed reflection (DBR) laser that oscillates at a center wavelength of 1.55 μm is used as the wavelength tunable semiconductor laser. The optical wavelength filter 2 is composed of an optical waveguide formed in a SiO ₂ layer deposited on a Si substrate, a directional coupler, and a grating type filter.
Corresponding to the Bragg wavelength of the diffraction grating, a directional coupler with an adjusted coupling length is formed on the light input side of the diffraction grating. Light with a wavelength that matches the Bragg wavelength of the diffraction grating is reflected by the diffraction grating. Then, the light is coupled to a light output waveguide different from the input side optical waveguide by the directional coupler, and is output from the light output section. The input signal light 10 is coupled to the wavelength tunable semiconductor laser 1 through the input optical fiber 3. The oscillated light intensity of the wavelength tunable semiconductor laser 1 is modulated by this input signal light, and wavelength conversion is realized. The oscillation light of the wavelength tunable semiconductor laser 1 can be controlled by injecting a current into the control current wire 7 for changing the oscillation wavelength of the laser. The input signal component 11 output through the wavelength tunable semiconductor laser 1 is
The light is reflected by the diffraction grating 20 formed in the optical wavelength filter 2, is output to the light output unit 30, and is then extracted by the output optical fiber 4. The wavelength-converted light is reflected by the diffraction gratings 21 to 24 whose periods are set in accordance with the wavelength, is output from the respective light output sections 31 to 34, and is taken out by the output optical fiber 5. Further, the light output units 31 to 35 for extracting the wavelength-converted light can be changed by changing the control current of the wavelength tunable semiconductor laser 1.

In this embodiment, an ordinary DBR laser is used as the wavelength tunable semiconductor laser, but the same configuration can be realized by using another wavelength tunable laser (for example, distributed feedback laser; DFB laser, etc.). it is obvious.
Further, in this embodiment, the glass waveguide type filter using the diffraction grating and the directional coupler is used as the optical wavelength filter, but an optical wavelength filter using another filter structure (for example, ring interferometer) is used. It is obvious that the same configuration can be realized by using it.

(Embodiment 2) FIG. 3 shows a second embodiment of the present invention. The present embodiment is characterized in that the wavelength tunable semiconductor laser 1 as the wavelength conversion element and the optical wavelength filter are formed on the same semiconductor (InP) substrate 200. Here, a DBR laser having a central wavelength of 1.55 μm was used as the wavelength tunable semiconductor laser. A semiconductor optical waveguide filter composed of diffraction gratings 20 to 24 and a directional coupler was used as the optical wavelength filter. The directional coupler is provided on the light input side of the diffraction gratings 20-24 and in the diffraction gratings 20-24. As a result, it is possible to realize a stable wavelength conversion system optical integrated circuit that is compact and has improved coupling efficiency between the wavelength conversion element and the optical wavelength filter. The operating principle is the same as that of the first embodiment.

Also in this embodiment, it is apparent that the wavelength conversion system optical integrated circuit having the same function can be realized by using a wavelength tunable semiconductor laser having another structure as the wavelength tunable semiconductor laser. Further, in the present embodiment, the semiconductor optical waveguide type wavelength filter composed of the diffraction grating and the directional coupler is used as the optical wavelength filter, but the same applies by using a filter having another structure (for example, a ring interferometer). It is obvious that an optical integrated circuit having the function of can be constructed.

[0014]

As described above with reference to the specific embodiments, according to the present invention, the wavelength of the input signal light is converted into another arbitrary wavelength, and the light corresponding to the wavelength of the converted light which is changed by the control current is changed. A wavelength conversion system that can extract converted signal light from the output position has been constructed. Further, the input signal light component could be extracted from the predetermined light output position without any change.

[Brief description of drawings]

FIG. 1 is an optical circuit diagram showing the concept of the present invention.

FIG. 2 is an optical circuit diagram showing a first embodiment of the present invention.

FIG. 3 is an optical circuit diagram showing a second embodiment of the present invention.

FIG. 4 is an optical circuit diagram showing the concept of a conventional system using wavelength conversion.

FIG. 5 is an optical circuit diagram showing the concept of a conventional wavelength conversion system via an electric circuit.

[Explanation of symbols]

 1 wavelength tunable semiconductor laser (wavelength conversion element) 2 optical wavelength filter 3 signal light input optical fiber 4 input signal light extraction optical fiber 5 wavelength conversion light extraction optical fiber 6 coupling optical fiber of wavelength conversion element and optical wavelength filter 7 conversion optical wavelength Current injection wire for control 10 Input signal light 11 Input signal light 12 extracted from the system 12 Wavelength conversion light 20-24 Diffraction grating 30 Input signal light extraction part 31-35 Wavelength conversion light extraction part 100 Wavelength conversion system 200 Semiconductor substrate

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kunishige Oe 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A wavelength conversion element and a wavelength filter, each of which is composed of at least one wavelength conversion element disposed in a signal light input section and oscillating at a single wavelength, and a wavelength filter whose optical output position changes depending on the wavelength. Is a wavelength conversion system characterized by being optically connected. 2. At least one wavelength conversion element arranged at a signal light input section and oscillating at a single wavelength, and a wavelength filter composed of a semiconductor waveguide whose optical output position changes according to wavelength are optically connected. A wavelength conversion system, which is integrated on the same semiconductor substrate in the assembled state.