JPH06120595A - Light wavelength converter circuit - Google Patents

Abstract

PURPOSE:To enable a light wavelength converter circuit to be operated at an extremely high speed by making up a wavelength filter of polarization isolation elements and a plurality of wavelength filters provided for two independent polarized lights. CONSTITUTION:Using a semiconductor laser 1 as a gain medium, a laser for light of the same polarization mode as the input light is comprised of the end face of the semiconductor laser 1 to which a nonreflective coating is not applied, and a mirror 52. The oscillation wavelength for this is set to ly by a wavelength filter 62. Similarly, using the semiconductor laser as a gain medium, the end face of the semiconductor laser 1 to which a nonreflective coating is not applied and a mirror 51 constitute a laser for light which is orthogonal with the input light and has the same polarization mode as the output light. The oscillation wavelength for this is set to lambdax by a wavelength filter 61. An output light 13 of the wavelength lambdax is output, and the light of the other polarization mode 16 does not oscillate. However, if an input light of the wavelength of lambday and the polarization mode 16 is input, the input light is amplified by the semiconductor laser to oscillate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical wavelength division multiplexing communication in the field of optical communications, and more particularly to an optical wavelength conversion circuit in a wavelength division type optical switch for exchanging optical signals on a wavelength division multiplexing optical transmission line as light. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a DBR (Distr.
In ibuted Bragg Reflector) type semiconductor laser,
An optical wavelength conversion circuit has been proposed which operates a part of the active layer as a supersaturation absorption region (Kondo et al., "Giga-bit O").
peration of Wavelength Conversion Laser ”, 1990
Alternative Topical Meeting on Photonic Swi
tching, 13D-9, 1990). FIG. 7 is a diagram showing the configuration of the optical wavelength conversion circuit, in which 21 is a first active region, 22 is a saturable absorption region, 23 is a second active region, 24 is a phase adjustment region, and 25 is a DBR region. .

FIG. 8 is a diagram for explaining the operation of FIG. 7, in which the horizontal axis represents the injection current into the second active region 23 and the vertical axis represents the output light intensity. As shown in FIG.
When the injection current is set to the bias point a, output light is not output without input light. Here, when input light is applied, the light absorption coefficient of the supersaturated absorption region 22 decreases, and the laser enters the oscillating state to output output light. Since the wavelength of the output light can be changed by adjusting the currents to the phase adjustment region 24 and the DBR region 25, the wavelength of the input light can be converted into a desired wavelength and output.

[0004]

In the above-described optical wavelength conversion circuit, since the changing speed of the optical absorption coefficient in the supersaturation absorption region is limited by the lifetime of the carrier, the modulation signal speed of the optical signal for wavelength conversion operation is Usually, it is limited to about nanoseconds, and there is a problem that it cannot operate at high speed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an optical wavelength conversion circuit capable of high speed operation.

The above and other objects and novel features of the present invention will be apparent from the description of this specification and the accompanying drawings.

[0007]

In order to achieve the above object, the optical wavelength conversion circuit of the present invention comprises a semiconductor laser diode with an external resonator and two semiconductor laser diodes arranged in the external resonator. A wavelength filter having means for adjusting wavelength transmission characteristics from the outside that independently selects and transmits a predetermined wavelength for each independent polarization mode, and a semiconductor laser diode with an external resonator by selecting light having a predetermined polarization mode And a means for selecting light having a predetermined polarization mode and extracting it from the semiconductor laser diode with an external resonator.

In the optical wavelength conversion circuit of the present invention,
The wavelength filter is composed of a polarization separation element and a plurality of wavelength filters provided for two independent polarized lights.

Further, in the optical wavelength conversion circuit of the present invention,
The wavelength filter is composed of an anisotropic medium having independent transmission characteristics for two independent polarization modes.

[0010]

According to the above-mentioned means, of the two independent polarization modes, only the polarization mode having a higher gain is laser-oscillated in the external resonator composed of the semiconductor laser and the mirror and is extracted as the output light. Be done. The wavelength of the light of this polarization mode is determined by the wavelength filter provided in the resonator.

The other polarization mode does not normally oscillate because laser oscillation is suppressed. However, when input light with the same polarization mode as this polarized light and having a wavelength determined by the wavelength filter provided in the resonator is input into the external resonator, the input light is amplified by the semiconductor laser and finally Will cause laser oscillation. At this time, the light of the other polarization mode, which has been lasing until then, is suppressed and the oscillation is stopped. Furthermore, when the input light is cut off, the gains of the light in the two polarization modes are adjusted so as to return to the initial state again.

That is, the above-mentioned operation is that the output light is modulated by the input light. When the input light is off, the output light is on, and conversely, the input light is When it is on, the output light is off.
The wavelengths of the input light and the output light can be set to the desired wavelengths by the wavelength filter provided in the external resonator. Since the input light and the output light have different polarization modes, they can be set independently for the two polarizations. By controlling the characteristics of the wavelength filter, the wavelength conversion operation can be performed from an arbitrary input wavelength to an arbitrary output wavelength. The input and output are inverted between on and off, but this does not matter because the information contained does not change. Inversion can also be prevented by passing the optical wavelength conversion circuit according to the present invention through an even number of stages.

By adjusting the transmission characteristics of the filter from the outside, it is possible to select a desired input light wavelength and convert it to a desired output light wavelength.

Further, the wavelength filter includes a polarization separation element,
Since it is composed of a plurality of wavelength filters provided for each of two independent polarized lights, the wavelength selection / conversion characteristics can be easily adjusted.

Further, since the wavelength filter is composed of an anisotropic medium having independent transmission characteristics for two independent polarization modes, the wavelength conversion operation is realized without separating the two polarization modes. be able to.

[0016]

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

(Embodiment 1) FIG. 1 is a diagram showing Embodiment 1 of an optical wavelength conversion circuit according to the present invention, in which 1 is a semiconductor laser and 2 is a non-reflective coating applied to one output end face of the semiconductor laser 1. 3 is a current supply terminal, 4 is a polarization separating element for separating light of two orthogonal polarization modes output from the semiconductor laser 1, 51 and 52 are of the respective polarization modes separated by the polarization separating element 4. Light the semiconductor laser 1
Partial reflection mirror elements (hereinafter referred to as mirrors) for returning the light to the light source, 61 and 62 are wavelength filters provided for each light of each polarization mode separated by the polarization separation element 4, and 71 and 72 are wavelength filters 61 respectively. , 62 is an electric terminal for adjusting the transmission wavelength of the light beam, 8 is a polarization separation element for extracting only a desired polarization mode from the input light and inputting it to the semiconductor laser 1, and 9 is an antireflection coating for the input light of the semiconductor laser. A lens for coupling to the end face which is not formed, 10 is a lens for optical coupling, 11 is a lens for coupling the transmitted light from the mirror as output light to the outside, 1
Reference numeral 2 is input light, and 13 is output light.

Among these constituent elements, the semiconductor laser 1 is used as a gain medium, and the end face of the semiconductor laser 1 which is not reflection-coated and the mirror 52 constitute a laser for the light of the same polarization mode as the input light. The oscillation wavelength at this time becomes λy due to the wavelength filter 62. Also,
Similarly, using the semiconductor laser 1 as a gain medium, the non-reflection coated end surface of the semiconductor laser 1 and the mirror 51 constitute a laser for light that is orthogonal to the input light and has the same polarization mode as the output light. The oscillation wavelength at this time is
It becomes λx due to the wavelength filter 61.

FIG. 2 is a diagram showing two orthogonal polarization modes of light used in the wavelength conversion circuit according to the present invention. The x direction is parallel to the semiconductor substrate surface of the semiconductor laser 1, and the y direction is. The vertical direction. Reference numeral 15 is a polarization mode in which the electric field vibration direction of the oscillated light is the x direction, and 16 is a polarization mode in the y direction.

FIG. 3 shows the filter characteristics used in the wavelength conversion circuit according to the present invention, where the horizontal axis is the wavelength and the vertical axis is the light transmittance. As shown in FIG. 3, it has a transmission characteristic having a peak at λx for the polarization mode 15 and a peak at λy for the polarization mode 16.

FIG. 4 is a diagram showing an example of a wavelength filter having the above-mentioned filter characteristic, and Hirabayashi et al.
"Narrow-band tunable wavelength-selective filter
s of Fabry-Perot interferometers with a liquid cr
ystal intracavity ”, IEEE Photonics Technol
Ogy Letters, vol.3, pp.213-215, Mar. 1991 and the like. 17 is a liquid crystal, 18-1 and 18-2 are dielectric mirrors, 19-1 and 19-2 are transparent electrodes, 20-1 and 20-2.
0-2 is a glass substrate with an antireflection coat. A voltage V is applied between the transparent electrodes 19-1 and 19-2, and the transmission wavelength characteristic can be changed.

In the structure shown in FIG. 1, since the gain for the light of the polarization mode 15 is large in the ordinary semiconductor laser,
The output light 13 of the wavelength λx is output, and the oscillation of the light of the other polarization mode 16 is suppressed and does not oscillate. However, when input light of wavelength λy and polarization mode 16 is input, the input light is amplified by the semiconductor laser and oscillates. At this time, the light of the polarization mode 15 that was initially oscillated is conversely suppressed and the oscillation is stopped, so that the output light disappears.

FIG. 5 is a diagram for explaining an operation example of the optical wavelength conversion circuit according to the first embodiment, in which the horizontal axis represents time and the vertical axis represents light intensity. In FIG. 5, the input light of wavelength λy is “1”.
This is an example of the case where the intensity is modulated in the pattern of 1010100 ″, and it can be seen that the light of the wavelength λx, which is the opposite of the pattern of the input light, is output as “00101011”.

(Embodiment 2) FIG. 6 is a schematic configuration diagram showing a schematic configuration of Embodiment 2 of the optical wavelength conversion circuit of the present invention.
Is a semiconductor laser, 2 is an antireflection coating applied to one output end face of the semiconductor laser 1, 3 is a current supply terminal, 5 is a mirror for returning light to the semiconductor laser 1, 6 is a wavelength filter, and 8 is input light. A polarization splitting element for extracting only a desired polarization mode and inputting it to the semiconductor laser 1, 9 is a lens for coupling the input light to an end face of the semiconductor laser which is not anti-reflection coated, and 10 is for optical coupling. A lens, 11 is a lens for coupling the transmitted light from the mirror as output light to the outside, 12 is input light, 13 is output light, 1
Reference numeral 4 denotes a polarization separation element that extracts and outputs only a desired polarization mode from the two polarization modes.

The optical wavelength conversion circuit of the second embodiment is different from that of the first embodiment in the structure of the wavelength filter, and the basic operation principle utilizing the competition of two polarization modes is the same.

In the first embodiment, after the light of two polarization modes is separated by the polarization separation element 4, the input wavelength and the output wavelength are set by the wavelength filters 61 and 62 provided for each mode. . On the other hand, in the first embodiment, the wavelengths of light in the two polarization modes are independently set by the single wavelength filter 6 that uses an anisotropic medium having different refractive indices in the x direction and the y direction. is doing. Such a wavelength filter can be realized by the filter shown in FIG. That is, the liquid crystal 17 in FIG.
Has a different index of refraction for polarization modes 15 and 16, thus allowing the wavelength conversion operation according to the invention with a single filter.

As described above, the invention made by the present inventor is
Although the specific description has been given based on the above-described embodiments, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

[0028]

As described above, according to the present invention, the operating speed of the optical wavelength conversion circuit does not depend on the carrier lifetime, and is determined only by the axial length of the optical wavelength conversion circuit. , Can be operated at extremely high speed.
Further, it can be manufactured in a small size.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a schematic configuration of a first embodiment of an optical wavelength conversion circuit of the present invention,

FIG. 2 is a diagram for explaining two orthogonal polarization modes of light in Example 1;

FIG. 3 is a diagram for explaining wavelength transmission characteristics of a wavelength filter used in the optical wavelength conversion circuit according to the present invention,

FIG. 4 is a diagram showing an example of the configuration of a wavelength filter according to the first embodiment,

FIG. 5 is a diagram showing an operation example of the optical wavelength conversion circuit of the first embodiment according to the first embodiment;

FIG. 6 is a schematic configuration diagram showing a schematic configuration of a second embodiment of the optical wavelength conversion circuit of the present invention,

FIG. 7 is a schematic configuration diagram showing a schematic configuration of a conventional wavelength conversion circuit,

8 is a diagram for explaining the operation of the wavelength conversion circuit shown in FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor laser, 2 ... Non-reflective coating, 3 ... Current supply terminal, 4 ... Polarization separation element 51, 52 ... Partial reflection mirror element, 6, 61, 62 ... Wavelength filter, 71, 72 ... Electrical terminal, 8 ... Polarization Separation element, 9 ... Lens, 10 ... Lens, 11 ... Lens, 12 ...
Input light, 13 ... Output light, 14 ... Polarization separation element, 15 ... Polarization mode in which electric field vibration direction is x direction, 16 ... Polarization mode in which electric field vibration direction is y direction, 17 ... Liquid crystal, 18-1, 18-2
… Dielectric mirrors, 19-1, 19-2… Transparent electrodes, 20-
1, 20-2 ... Glass substrate with anti-reflection coating, 21 ... First
, 22 ... Supersaturated absorption region, 23 ... Second active region, 24 ... Phase adjusting region, 25 ... DBR region, V ... Voltage, λx, λy ... Wavelength.

Claims (1)

[Claims] 1. A semiconductor laser diode with an external resonator, and a wavelength transmission characteristic from the outside, which is disposed in the external resonator and independently selects and transmits a predetermined wavelength for each of two independent polarization modes of the semiconductor laser diode. , A means for adjusting light having a predetermined polarization mode, a means for selecting light having a predetermined polarization mode to enter the semiconductor laser diode with an external resonator, and a light having a predetermined polarization mode for selecting the external resonator. An optical wavelength conversion circuit comprising means for taking out the semiconductor laser diode.