JPH0626267B2 - Wavelength switching light source - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a semiconductor light source that can be configured in a small size and that can switch and generate light of two arbitrary desired wavelengths.

[Prior Art] Conventionally, as a configuration example of a light source for switching and generating light of two wavelengths, there is a configuration of FIG. In FIG. 4, 1
And 2 are light sources of semiconductor lasers having different wavelengths, 3 and 4 are drive circuits for the lasers 1 and 2, 5 is a timing circuit for controlling the drive circuits 3 and 4, and 6 is a light output from the lasers 1 and 2. It is a multiplexing circuit.

Now, when switching from the light source 1 to the light source 2, it is necessary to turn off the drive circuit 3 and turn on the drive circuit 4 by the timing circuit 5. Therefore, there are drawbacks in that the two drive circuits 3 and 4 are required and the timing circuit 5 is not required.

Further, when switching the output light between two or more wavelengths, it is necessary to provide a separate drive circuit corresponding to each light source, and the timing circuit selects the light source and sets the timing. Therefore, it is difficult to reduce the size and simplify the entire light source device.

Furthermore, in the case where the output port is a single mode system, there is a drawback in that the combining circuit 6 theoretically loses the combined damage. For example, a loss of 3 dB occurs in the two multiplexing circuits, and a loss of 6 dB occurs in the four multiplexing circuits.

[Objective] Therefore, it is an object of the present invention to perform wavelength switching with a single drive circuit without using a multiplexer, which is a factor causing the above-mentioned drawbacks, and to reduce the size. It is to provide a wavelength switching light source capable of

[Configuration of the Invention] In order to achieve such an object, in the present invention, light sources having different wavelengths are continuously connected. That is, the present invention is the first
A first semiconductor laser having an oscillation wavelength and at least one second semiconductor laser having a second oscillation wavelength shorter than the first oscillation wavelength are arranged so that the output light on the long wavelength side becomes the input light on the short wavelength side. Continuously connect from the side with the long oscillation wavelength to the side with the short oscillation wavelength.
The first semiconductor laser having the oscillation wavelength is always made to emit light, and the second semiconductor laser
By changing the magnitude of the injection current for the second semiconductor laser having the oscillation wavelength,
And light of one of the second oscillation wavelengths is selected and output.

In contrast to the conventional wavelength switching light source, the present invention has the advantage that only one drive circuit is provided for wavelength switching, the timing circuit is unnecessary, and the multiplexing circuit is unnecessary.

EXAMPLES The present invention will be described in detail below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. Where 11 is 1.55μ
A semiconductor laser having an oscillation wavelength of m, a semiconductor laser 12 having an oscillation wavelength of 1.30 μm, a constant current source 13 for driving the semiconductor laser 11, and a pulse drive circuit 14 for pulse-driving the semiconductor laser 12. Reference numeral 15 is a condenser lens for condensing the light from the laser 11 on the laser 12.

FIG. 1 also shows a measurement system for the switching light source having the above configuration, 16 is a single mode optical fiber, 17 is a spectroscope, and 18 is a spectroscope.
Is a condenser lens for condensing the light from the laser 12 on the optical fiber 16, and 19 is a condenser lens for condensing the light emitted from the optical fiber 16 on the spectroscope 17. 20 is a photodetector such as Ge-APD, 21 is a condenser lens for condensing the output light from the spectroscope 17 on the photodetector 20, and 22 is for amplifying the output from the high detector 20, for example, a gain of 20 dB Preamplifier, 23 is a preamplifier 22
Is a synchroscope for measuring the output from the pulse drive circuit 14 at the timing.

In this embodiment, the light source 11 having a wavelength of 1.55 μm and the light source 12 having a wavelength of 1.30 μm are switched by one pulse driving circuit 14, and the result actually measured by the oscilloscope 23 is shown in FIG. Show. In FIG. 2, single mode optical fiber 16
Is a time waveform in which the output light of 1 is dispersed by the spectroscope 17 and the optical signal of wavelength 1.30 μm and the optical signal of wavelength 1.55 μm are separately observed. The upper trace corresponds to 1.30 μm laser light and the lower trace corresponds to 1.55 μm laser light. That is, to the semiconductor laser 12 having an oscillation wavelength of 1.30 μm, a pulsed current having a time width of about 10 ns is applied while the current value increases from 0 to about 1.2 times the oscillation threshold value.
On the other hand, a semiconductor laser 11 with an oscillation wavelength of 1.55 μm is a constant current source 13
Oscillates constantly. As is clear from FIG. 2, when an optical signal with a wavelength of 1.30 μm is observed, a wavelength of 1.55
The signal light of μm is completely cut off. On the other hand, wavelength 1.
When the optical signal of 30 μm is not observed, the optical signal of wavelength 1.55 μm is detected. From this result, the pulse drive circuit
By controlling the light source 12 by 14, the wavelength of 1.30 μm
It can be seen that the light source 12 and the light source 11 having a wavelength of 1.55 μm can be switch-controlled.

The reason will be described below. That is, the semiconductor laser 11
Since the light having a wavelength of 1.55 μm from the photon has a photon energy smaller than the band gap energy in the active layer of the semiconductor laser 12 having a wavelength of 1.30 μm, it is transmitted almost without being absorbed here when there is no injection current. To do. On the other hand, when the drive pulse is supplied from the drive circuit 14 to the semiconductor laser 12 and the injection current becomes large, the wavelength of 1.30
A wavelength of 1.55 μm at the same time as the output of μm light
Light is absorbed in the active layer of the semiconductor laser 12 by free carrier absorption and is not output. Therefore, by controlling the injection current of the semiconductor laser having the shorter oscillation wavelength, it is possible to switch between the two wavelengths and control the output.

FIG. 3 shows another embodiment of the present invention, in which 31, 32 and 33 are semiconductor lasers having lasing wavelengths of λ ₁ , λ ₂ and λ ₃ , respectively, wherein Is λ ₁
There is a relation of> λ ₂ > λ ₃ . 34, 35 and 36 are constant current sources for supplying a predetermined drive current to the semiconductor lasers 31, 32 and 33, respectively, and 37 is one pulse drive circuit commonly provided for the semiconductor lasers 31, 32 and 33, 38, 39 and 4
Reference numeral 0 denotes a coupling waveguide between the semiconductor lasers 31, 32 and 33. In this case, since there are three wavelengths to be switched, the following wavelength switching is possible.

The wavelength λ ₂ / λ ₁ can be switched by turning on the laser 31 (λ ₁ ), turning off the laser 33 (λ ₃ ) and turning on / off the laser 32 (λ ₂ ).

The wavelength λ ₃ / λ ₂ can be switched by turning off the laser 31 (λ ₁ ), turning on the laser 32 (λ ₃ ) and turning on and off the laser 33 (λ ₃ ).

The wavelength λ ₃ / λ ₁ can be switched by turning on the laser 31 (λ ₁ ), turning off the laser 32 (λ ₃ ) and turning on / off the laser 33 (λ ₃ ).

In the case of the embodiment shown in FIG. 3, the three-wave switching light source has been described, but the same applies to the case of four or more waves, and the present invention is effectively applied to a switching light source that obtains switching output of any desired plural wavelengths. be able to.

[Effect] As described above, in the present invention, the semiconductor laser elements having different wavelengths are continuously connected, and the oscillation timing of one of the elements is controlled to switch between the output wavelengths. The following advantages are obtained.

(1) The device can be downsized because the element structure is simple.

(2) The drive circuit is simplified and no timing circuit is required.

(3) Insertion loss is small because no multiplexing circuit is required.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a waveform diagram showing an example of a wavelength switching waveform observed in the configuration of FIG. 1, and FIG. 3 is another embodiment of the present invention. FIG. 4 is a block diagram showing a configuration example of a conventional wavelength switching light source. 1,2,11,12,31,32,33 …… Semiconductor laser, 3,4,14,37 …… Drive circuit, 5 …… Timing circuit, 6 …… Multiplexing circuit, 13,34,35,36 ...... Constant current source, 15,18,19,21 …… Condensing lens, 16 …… Single mode fiber, 17 …… Spectroscope, 20 …… Photodetector by Ge-APD, 22 …… Previous On-amplifier, 23 ... Synchroscope, 38, 39, 40 ... Coupling waveguide.

Claims (1)

[Claims] 1. A first semiconductor laser having a first oscillation wavelength,
At least one second semiconductor laser having a second oscillation wavelength shorter than the first oscillation wavelength, from the longer oscillation wavelength side to the shorter one so that the output light on the long wavelength side becomes the input light on the short wavelength side. The second semiconductor laser is continuously connected and the first semiconductor laser having the first oscillation wavelength is always made to emit light, and the magnitude of the injection current to the second semiconductor laser having the second oscillation wavelength is changed, thereby A wavelength switching light source, wherein light of one of the first and second oscillation wavelengths is selected and output.