JPH0878787A - Variable-wavelength light source device - Google Patents

Abstract

PURPOSE: To provide the light of a scattering wavelength interval by forming a ring resonator of a ring-like optical path including a filter for transmitting a plurality of wavelengths, a filter for transmitting a single wavelength and a light amplifier and only by selecting one of fixed wavelengths. CONSTITUTION: Spontaneous light from a light amplifier 11 passes through a light isolator 12 and enters into a periodic wavelength transmission filter 13 having a periodic transmission characteristic relative to a light wavelength. The transmissible wavelength of the output is scattered. An oscillation wavelength is limited by transmitting only one of λ1, λ2,...λn through a single- wavelength transmission filter 14. At that time, in the scattering oscillation wavelength determined by the periodic wavelength transmission filter 13 and the single-wavelength transmission filter 14. A wavelength variable mechanism changes the center frequency of the single-wavelength transmission filter, so that the scattering wavelength variable characteristic may be realized by selecting it one by one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to optical communication, optical information processing,
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device in the field of optical measurement, and more particularly to a light source device that obtains light of a single wavelength and a plurality of wavelengths that are variable in wavelength at discrete wavelength intervals.

[0002]

2. Description of the Related Art In the fields of optical communication, optical information processing, optical measurement, etc., it is necessary to create wavelength-multiplexed optical signals. For example, in the field of optical communication, there is wavelength multiplexing communication in which a signal having a different optical wavelength for each information is multiplexed into one optical fiber and communication is performed for each wavelength.
In this case, a light source device capable of switching arbitrary wavelengths or transmitting light of a plurality of wavelengths is required. For this purpose, wavelength tunable control is required to switch the transmission channel, and it is necessary to control the wavelength of the light source with high precision in order to match the wavelengths on the transmission side and the reception side. Further, it is necessary to make the intervals of the respective communication channels even.

FIG. 19 shows an apparatus for controlling a frequency interval in a conventional light source device. In FIG. 19, 61a to 6a
1c is a single wavelength variable light source device, 62 is a multiplexer,
63 is a branching device, 64 is a scanning Fabry-Perot etalon, 6
5 is a control signal generating means, 66a to 66c are control signal lines,
Reference numeral 17 is an optical fiber.

Next, the operation of the conventional example will be described with reference to FIG. FIG. 19 shows a wavelength spacing control device that keeps the wavelength spacing of a plurality of light sources constant. There are a plurality of optical signal outputs from the single wavelength variable light source devices 61a to 61c, each of which outputs a single wavelength, and each is connected to the multiplexer 62 by the optical fiber 17. The multiplexer 62 joins the outputs from the plurality of single-wavelength light source devices 61a to 61c and passes the plurality of optical wavelengths through one optical fiber. A part of the output from the combined optical fiber is branched by the branching device 63 and guided to the scanning Fabry-Perot etalon 64. The scanning Fabry-Perot etalon 64 is obtained by temporally changing the transmission center wavelength of the Fabry-Perot etalon filter. Every time the scanning center wavelength of the scanning Fabry-Perot etalon is scanned by inputting the wavelength-multiplexed signal to the scanning Fabry-Perot etalon 64 and changing the wavelength signal of light into an electric signal by the control signal generating means 65, Information on each wavelength of the wavelength division multiplexed signal is converted into a change in the output voltage on the time axis, and an error signal with a wavelength shift for matching the wavelength intervals is output. The signal from the control signal generating means 65 is the control signal line 66.
a to 66c are input to the single wavelength variable light source devices 61a to 61c, the oscillation wavelength intervals are controlled to be uniform, and the oscillation wavelength intervals are controlled to be constant.

Therefore, in order to obtain light of a desired light wavelength, the means 14 having a single transmission characteristic for the light wavelength in the single wavelength variable light source devices 61a to 61c is accurately changed. There was a need. Furthermore, in the case of obtaining a wavelength division multiplexed signal having a plurality of optical wavelengths, the wavelengths of a plurality of light source devices are required at discrete wavelength intervals, and in that case, a wavelength interval control device for aligning the wavelength intervals of the respective light sources Was needed.

A light source device 6 having a single wavelength and variable wavelength as shown in FIG.
As an example of No. 1, there is one as disclosed in Japanese Patent Laid-Open No. 175577/1993. FIG. 20 is an explanatory diagram showing a conventional light source device. In FIG. 20, 111 is a rare earth-doped optical fiber, 113 is a pump laser diode, 112 is a multiplexer that joins the output of the pump laser diode and the ring resonator, 12 is an optical isolator, and 14 is a single transmission for the optical wavelength. A wavelength selection filter having characteristics, 15 is a coupler for branching the optical power returned to the ring and the optical power to be output, 16 is a polarization controller for adjusting the polarization state in the optical fiber loop, and 17 is a combination of each in a ring shape. It is an optical fiber.

The operation of this conventional single-wavelength light source device will be described with reference to FIG. The output of the pumping laser diode 113 for pumping the fiber amplifier is multiplexed with the optical fiber loop 17 by the multiplexer 112 and input to the rare earth-doped fiber 111, and 111 is pumped by the output of 112 and the optical amplification means. To work as.
At this time, the optical isolator 12 prevents the output from the multiplexer 112 from returning in a direction opposite to the direction of the light in the optical fiber ring. It is fed back in a ring shape by the optical fiber loop in FIG. 20, and laser oscillation occurs when the gain becomes larger than the loss of the fiber ring. The means 14 having a single transmission characteristic with respect to the light wavelength oscillates at a wavelength at which the transmission loss is minimized. Here, the wavelength at which light is oscillated selectively is determined from the gain wavelength range of 111 by changing the transmission center wavelength of the means 14 having a single transmission characteristic with respect to the light wavelength.
However, it is not easy to continuously adjust the transmission wavelength to a preset desired frequency, and a complicated external control device is required.

In the above-mentioned conventional example, when a plurality of light source devices are present, in order to make the respective wavelength intervals uniform, the output wavelengths from the plurality of wavelength tunable light sources are combined and then the respective oscillation wavelengths are adjusted. The wavelength spacing control device described above had to be provided as control for setting a specific spacing.

[0009]

Since the conventional light source is constructed as described above, when a plurality of light sources having different wavelengths are required, a plurality of single wavelength light sources are prepared and each of the light sources is provided. There is a problem in that it is necessary to control each oscillation wavelength, and further, a complicated wavelength spacing control device that performs precise control over two stages to uniformly control the oscillation wavelength spacing is also required. Further, in the light source device that obtains a single wavelength by selecting from a certain range of wavelengths, there is a problem that the selection control is complicated.

The present invention has been made in order to solve such a problem, and does not require a complicated wavelength spacing control device, and only one of the predetermined wavelengths is selected to provide a discrete wavelength spacing. It is an object of the present invention to obtain a light source device capable of obtaining the above light and having a wide wavelength selection range.

[0011]

A variable wavelength light source device according to the present invention has a plurality of wavelength transmission filters having characteristics of transmitting at a plurality of preset wavelengths and blocking at other wavelengths, and one of these transmission wavelengths. A ring resonator is formed by a ring-shaped optical path including a single wavelength transmission filter having a characteristic of selectively transmitting one wavelength, a plurality of wavelength transmission filters and the single wavelength transmission filter, and including an optical amplifier. The source of light is generated at the selected wavelength of the single wavelength transmission filter.

Further, a multi-wavelength transmission filter having a characteristic of transmitting at a plurality of preset wavelengths and blocking at other wavelengths, and a single wavelength having a characteristic of selectively transmitting one of the transmission wavelengths. A plurality of transmission filters, a plurality of wavelength transmission filters, and the above-mentioned single wavelength transmission filter in each of the branched optical paths are branched, and a ring resonator is formed by a ring-shaped optical path including an optical amplifier. The light source is generated at the selected wavelength of the above single wavelength transmission filter.

Further, in addition to the basic structure, an optical modulator is included in the ring, and the light source output is the optical modulation output.

Furthermore, the optical amplifier is an optical amplifier using an optical fiber doped with rare earth ions.

Alternatively, the optical amplifier is a semiconductor laser amplifier.

Furthermore, the semiconductor laser amplifier is provided with a drive current modulator to modulate the drive current of the semiconductor laser amplifier.

The variable wavelength light source device according to the present invention has a multi-wavelength transmission filter having a characteristic of transmitting at a plurality of preset wavelengths and blocking at other wavelengths, and one of these transmission wavelengths.
A single-wavelength reflector that selectively reflects one wavelength and partially transmits, a multiple-wavelength transmission filter and the above-mentioned single-wavelength reflector, and a linear optical path that includes an optical amplifier and a reflector. A Fabry-Perot cavity was created to generate the light source at the selected wavelength of the single wavelength reflector.

Furthermore, an optical modulator is included in the linear optical path,
The light source output was the light modulation output.

The optical amplifier is an optical amplifier using an optical fiber doped with rare earth ions.

The optical amplifier is a semiconductor laser amplifier.

Further, the semiconductor laser amplifier is provided with a drive current modulator, and the drive current of the semiconductor laser amplifier is modulated.

[0022]

In the wavelength tunable light source device according to the present invention, the resonance wavelength is determined by the transmission wavelength of the multiple wavelength transmission filter, and the ring resonator resonates at the selected wavelength of the single wavelength transmission filter that is selectively selected from the resonance wavelengths. Then, a light source is generated.

In the wavelength tunable light source device according to the present invention, the resonance wavelength is determined by the transmission wavelengths of the plural wavelength transmission filters, and the ring resonance is performed at the selected wavelengths of the plurality of single wavelength transmission filters selected from the resonance wavelengths. And a multi-wavelength light source is generated.

Furthermore, the light source is optically modulated to form a light source composed of a high-speed optical pulse train.

Furthermore, the light source is amplified by an optical fiber amplifier.

Furthermore, the light source is amplified by a semiconductor laser amplifier, and the light source is generated over a wide wavelength range.

Furthermore, the light source is amplified by a semiconductor laser amplifier, and at the same time light-modulated to form a stronger light source.

In the tunable light source device according to the present invention, the resonance wavelength is determined by the transmission wavelength of the multiple wavelength transmission filter, and the Fabry-Perot resonator is selected by the single wavelength reflector selected from the wavelengths. A light source is generated by resonating.

Further, the light source is optically modulated to form a light source composed of a high-speed optical pulse train.

Furthermore, the light source is amplified by an optical fiber amplifier.

Furthermore, the light source is amplified by a semiconductor laser amplifier, and the light source is generated over a wide wavelength range.

Further, the light source is amplified by a semiconductor laser amplifier and is simultaneously light-modulated to form a light source composed of a high-speed optical pulse train.

[0033]

【Example】

Example 1. If a plurality of wavelengths are set in advance and the light source device is configured to select a light source of an arbitrary wavelength from the set wavelengths, selection control or amplification control at the selected wavelengths may be performed. The device becomes simple. In this embodiment, a variable wavelength light source device having such a configuration will be described. FIG. 1 is an overall configuration diagram of an embodiment of a light source device according to the present invention. In FIG. 1, 11 is a means having an optical gain (optical amplifier), 12 is an optical isolator that circulates light only in a single direction, and 13 is a means having a periodic transmission characteristic with respect to an optical wavelength (periodic wavelength transmission). Filter), 14 means having a single transmission characteristic with respect to the light wavelength (single wavelength transmission filter), 15 means for branching light, 16 means for controlling polarization in a fiber ring, and 17 means for each An optical fiber that connects components in a ring shape. Figure 2
Is an example of an optical amplifier used in the embodiment of FIG. In FIG. 2, 111 is an optical fiber in which a part of the optical fiber is doped with rare earth, 112 is a multiplexer for coupling the output of the pumping laser diode and the ring resonator, 113
Is a laser diode that excites the rare-earth-doped optical fiber, 114 is a drive current source for operating the excitation laser diode, 115a and 115b are optical isolators, and 116, 116a, and 116b are lights that connect their optical components. Fiber.

The operation of the light source device having the above structure will be described with reference to FIGS. First, the optical amplifier of FIG. 2 will be described. The pump laser diode 113 is a current source 11
The drive current of 4 is supplied and it oscillates. Output of pumping laser diode 113 and input side optical fiber 115
The amplified optical signal input from a is the multiplexer 112.
They are multiplexed by and are input to the rare earth-doped fiber 111. The optical level of the rare earth-doped fiber 111 is pumped by the optical wavelength component of the pump laser diode 113,
Stimulated emission occurs only for input light in a certain wavelength band, causing optical amplification. The optical isolators 115a and 115b pass the light only in one direction, so that the light generated from the pump laser diode and the rare earth-doped fiber does not return to the input side, and the light on the output side does not enter the rare earth-doped fiber. It is performing various actions. In the configuration of FIG. 2, the pump laser diode is input in the forward direction with respect to the direction of the optical isolator, but the multiplexer 112 is arranged to the right of the rare earth-doped fiber 111 to A configuration of reverse pumping in which a pump laser diode is input in the direction opposite to the direction of the isolator may be used. Further, it is possible to increase the pumping power by adopting a configuration in which forward pumping and reverse pumping are used together.

As the rare earth-doped fiber 111, specifically, an optical fiber partially doped with erbium can be used. The operating wavelength band of optical amplification in this case is 1.55μ
It is around m. Such a pump laser diode 113 for pumping an erbium-doped fiber is 1.49 μm.
A semiconductor laser in the vicinity or a semiconductor laser in the vicinity of 0.98 μm is suitable. Also, if a rare earth element other than erbium, such as neodymium or praseodymium, is added to a part of the optical fiber, optical amplification operation in the 1.3 μm band becomes possible.

FIG. 3A is a diagram showing an example of the transmission characteristics of the periodic wavelength transmission filter which is an important component in this embodiment. In FIG. 1, the spontaneous emission light generated by the optical amplifier 11 passes through the optical isolator 12 and shows its transmission characteristic in FIG. Enter the filter 13. FIG.
Since it has the transmission characteristic of (a), its output has discrete wavelengths that can be transmitted. That is, oscillation occurs at any of the transmission wavelengths λ1, λ2, ... λn shown in FIG. This output is transmitted by the single wavelength transmission filter 14 as shown in FIG. 3 (b) by λ1, λ2, ... λn.
Only one of them is transmitted and the oscillation wavelength is limited. This optical output continues to the optical coupler 15 having a certain branching ratio so that a part of the light is output from the ring resonator, and the remaining part is input to the polarization controller 16 to adjust the polarization state, and again. It is input to the optical amplifier 11. These optical components are connected in a ring shape by an optical fiber 17 to form a ring resonator. At this time, the wavelength tunable mechanism operates at a discrete oscillation wavelength determined by the periodic wavelength transmission filter 13 and the single wavelength transmission filter 14,
By changing the center frequency of the single wavelength transmission filter, only that wavelength is oscillated, and by sequentially selecting this wavelength, discrete wavelength tunable characteristics are realized. Further, the arrangement position of each part constituting the ring resonator is not limited to this embodiment.

As the periodic wavelength transmission filter 13 for the optical wavelength as shown in FIG. 3A, there is specifically a fiber Fabry-Perot optical filter. Fabry-Perot optical filter
It has two mirrors formed by polishing the input and output ends of a single mode fiber and coating them. The mirror is separated by an air gap, and the transmission center wavelength of the filter can be changed by changing the length of the air gap. If this gap length is set in advance, it is possible to give transmission characteristics at arbitrary discrete wavelengths.
Further, a liquid crystal can be used between the mirrors. In addition, the periodic transmission characteristic of the Mach-Zehnder interferometer, which is made of a silica-based waveguide, can be similarly used.

As the single wavelength transmission filter 14, specifically, there is one in which a dielectric multilayer filter is built as a bandpass filter. In this case, the variable transmission wavelength mechanism can be realized by changing the angle of light incident on the dielectric multilayer film. In addition, the acousto-optic filter has a unit that has a single transmission characteristic for the light wavelength, based on the principle that the light wavelength can be selectively converted into TE and TM by the interaction between ultrasonic waves and light. You can also do it. In this case, the transmission wavelength variable mechanism can change the transmission center wavelength by changing the frequency of the ultrasonic wave.

Embodiment 2 FIG. In this embodiment, a light source device that simultaneously generates light having a plurality of wavelengths will be described. FIG. 4 is an overall configuration diagram of another embodiment of the light source device according to the present invention. In the figure, 14a and 14b are single wavelength transmission filters that select different wavelengths, 21 is an optical branching device, and 22a and 22b.
Is an optical attenuator. The other optical amplifier 11, isolator 12, periodic wavelength transmission filter 13, optical branch 15, and polarization controller 16 are the same as in the first embodiment.

In the above embodiment, one light source device outputs one single wavelength. However, as shown in FIG. 4, the output of an optical filter having a periodic transmission characteristic with respect to an optical wavelength. Is branched into two optical paths by an optical branching device 21, each of which has means 14a and 14b having a single transmission characteristic for an optical wavelength next to the branching destination, and thereafter has an optical attenuator 22.
a, 22b, and the optical coupler 15 merges and connects to the fiber ring. After splitting into two by the optical branching device, the wavelength to be oscillated is selected by means having a single transmission characteristic with respect to the optical wavelength, and then the gain of each of the two rings branched by the optical attenuator is selected. Is made uniform, and a plurality of wavelengths can be oscillated. This configuration corresponds to the conventional configuration of FIG. 19 and has an effect of simplifying the configuration by reducing the number of optical amplifiers for obtaining light sources of a plurality of wavelengths.

As a modification of the above embodiment, there is a configuration shown in FIG. It is realized by using a Mach-Zehnder interferometer 31 in combination with the means (periodic wavelength transmission filter) 13 having periodic transmission characteristics for the optical wavelength of FIG. 4 and the optical branching device 21.

FIG. 6 shows a conceptual diagram of the Mach-Zehnder interferometer 31. Further, FIG. 7 is a diagram for explaining the characteristic. In FIG. 6, 311 is an optical input port, 312, and 3.
Reference numeral 13 is an optical output port, 314 is an optical fiber, and 315 is an optical coupler. The operating principle of the Mach-Zehnder interferometer will be briefly described. Optical input port 31
The light input from 1 is split into two by the optical coupler 315, connected to the optical fibers having a difference in optical path length between the two, and rejoined by the optical coupler 315. At this time, due to the difference in optical path length between the two optical fibers 314 divided into two parts, the periodic transmission characteristics for the optical wavelengths as shown in FIG.
Will appear in 3. In this embodiment, the light output ports 312 and 313 are connected to 14a and 14b, respectively.

Example 3. By inserting a modulator into the ring resonator of the light source, mode-locked oscillation occurs,
A high-speed optical pulse train can be obtained. FIG. 8 is an overall configuration diagram of another embodiment of the light source device according to the present invention. In the figure,
41 is a light intensity modulator, 42 is a sine wave signal oscillator, 41
And 42 constitute means for modulating the light loss at a predetermined frequency. Other optical amplifiers 11 and optical isolators 1
2, the periodic wavelength transmission filter 13, the single wavelength transmission filter 14, the optical branch 15, and the polarization controller 16 are the same as the elements of the above embodiment.

In this embodiment, in addition to the structure of the first embodiment, an optical modulation means for modulating the light loss consisting of an optical intensity modulator 41 and a sine wave signal generator 42 at a predetermined frequency is provided in the ring resonator. It is applied to a wavelength tunable mode-locked laser.

The operation of this configuration will be described. In a ring resonator, there are many longitudinal modes with oscillation wavelength intervals given by fr = c / L (c: speed of light, L: length of ring resonator).
Here, when optical modulation of frequency fm = fr is applied by the light intensity modulator 41 and the sine wave signal generator 42 in the ring resonator,
A mode-locked oscillation state in which the phases of all longitudinal modes at the wavelength interval fr are aligned and an optical pulse train with a repetition period 1 / fr is obtained. As the light intensity modulator 41 in the ring resonator, for example, an intensity modulator based on an electro-optic effect using lithium niobate as a high speed light intensity modulator can be used.
It can also be realized by modulating the drive current of the semiconductor laser type optical amplifier described later at high speed.

Example 4. It is also possible to combine the second embodiment and the third embodiment. FIG. 9 is an overall configuration diagram of another embodiment of the light source device according to the present invention. In the figure, an optical amplifier 1
1, optical isolator 12, periodic wavelength transmission filter 1
3, single wavelength transmission filters 14a, 14b, optical branch 1
5, 21, the polarization controller 16, the optical attenuators 22a and 22b,
The optical modulator 41 and the sine wave signal transmitter 42 are the same constituent elements as in the above embodiment.

This embodiment is the same as the second embodiment but the third embodiment.
The ring resonator shown in FIG. 3 is provided with an optical modulator for modulating the loss of light at a predetermined frequency, and is applied to a wavelength tunable mode-locked laser capable of obtaining a plurality of wavelengths.

Example 5. Also, as the optical amplifier 11, FIG.
There is also a configuration shown in FIG. In the figure, 116a,
116b is an optical fiber for optical input and optical fiber for optical output, 1
15a and 115b are optical isolators that allow light to pass in only one direction, 118a and 118b are lens coupling portions for coupling an optical fiber and a semiconductor laser optical amplifier, respectively.
Reference numeral 114 is a current source for operating the semiconductor laser type optical amplifier, and 117 is a semiconductor laser type optical amplifier.

As the semiconductor type laser optical amplifier 117, a semiconductor laser whose end face is coated with an antireflection film can be used. Although the structure of this structure requires precision, it has a wide band and can broaden the selection range of wavelengths. This optical amplifier can be applied to any of the first to fourth embodiments.

Example 6. A configuration in which the number of elements for light modulation is further reduced will be described. FIG. 11 is an overall configuration diagram of an embodiment of a light source device according to the present invention. In the figure, 12 to 1
The respective constituent elements of No. 7, the sine wave signal oscillator 42, and the semiconductor laser type amplifier 117 are equivalent to the corresponding elements of the other embodiments.

In the present embodiment, a semiconductor laser type amplifier is used as the optical gain means in the fourth example, and the driving current of the semiconductor laser type amplifier is modulated at high speed, so that the optical intensity modulator 41 and the means 11 having the optical gain are provided. It also has a configuration that doubles as.

FIG. 12 shows the structure of a semiconductor laser type optical amplifier in this embodiment. Current source 114,
Optical isolators 115a and 115b, optical input fiber 1
16a, the optical output fiber 116b, the semiconductor laser type optical amplifier 117, the lens coupling parts 118a and 118b are respectively equivalent to the corresponding elements of the above-mentioned respective embodiments. The drive current of the semiconductor laser type optical amplifier is converted into a sine wave signal generator 42.
By modulating with, the gain can be modulated at high speed, and the loss of light is modulated with a predetermined frequency. As the semiconductor type laser optical amplifier 117, a semiconductor laser whose end face is coated with an antireflection film can be used.

Example 7. Although all of the above embodiments are ring type resonators, other types of linearly arranged structures will be described. FIG. 13 is an overall configuration diagram of an embodiment of a light source device according to the present invention. Reference numeral 51 is a light reflector, and reference numeral 52 is a single light wavelength reflector having a reflection characteristic with respect to a light wavelength of only a single wavelength and capable of varying the reflection wavelength. Other optical amplifier 11, optical isolator 12, periodic wavelength transmission filter 1
3. The optical fiber 17 is equivalent to the corresponding element of the other embodiments. FIG. 14 is a diagram for explaining the characteristics of the single light wavelength reflector 52 and its selecting operation.

The spontaneous emission light generated by the optical amplifier 11 is reflected by the optical reflector 51 and input again to the optical amplifier 11, and the periodic wavelength transmission filter 13 transmits only the light of a wavelength having a constant interval. Then, it is input to the single light wavelength reflector 52 having the transmission characteristic as shown in FIG.
Here, since the characteristics of the single-light wavelength reflector 52 reflect only a certain selected wavelength, only the transmission characteristics from the periodic wavelength filter 13 and the wavelength that matches the selected reflection wavelength of the single-light wavelength reflector 52. The reflected light is input to the optical amplifier 11 again. By repeating this, only the light wavelength component reflected by the single light wavelength reflector 52 is repeatedly reflected to cause laser oscillation. The output is limited by the optical isolator 12 to light in one direction and is output. At this time, only the reflection wavelength of the single light wavelength reflector 52 is output. Further, a wavelength tunable light source device is obtained by selectively changing the reflection wavelength of the single light wavelength reflector 52 as shown in FIG. At this time, the periodic wavelength transmission filter 13 can oscillate only the wavelengths set in advance, for example, the wavelengths shown in FIG. 14C, and oscillate at discrete wavelength intervals as shown in the first embodiment. Similar to the selective control of the single-wavelength transmission filter of the ring resonator, it is sufficient to simply select or control the laser oscillation at the selected wavelength, and the configuration and control are simple. In the first embodiment, an example of the ring laser is shown, but in this embodiment, the light reflector 51 and the single light wavelength reflector 5 are used.
It is applied to a Fabry-Perot type laser between two.

FIG. 15 shows an optical amplifier 1 used in this embodiment.
1 shows a specific example. In FIG. 15, 111 is a rare earth-doped optical fiber, 112 is a multiplexer that combines the optical output of the pump laser and the optical input to be amplified, and 113 is the pumping necessary for the rare earth-doped fiber of 111 to perform optical amplification. A pumping laser diode for bringing the pumping laser diode into a state and a current source 114 for oscillating the pumping laser diode.

The optical level of the rare earth-doped fiber 111 is pumped by the pumping laser diode 113, and stimulated emission occurs only for the optical input in a certain wavelength band to cause optical amplification. 111 rare earth doped fibers are
Specifically, an optical fiber to which erbium is partially added can be used. The operating wavelength band in this case is 1.55
It is around μm. Such a semiconductor laser having a wavelength of 1.49 μm as the wavelength of the pumping laser diode 113 suitable for pumping into the erbium-doped fiber, or 0.
A semiconductor laser of around 98 μm is suitable. Moreover, if a rare earth element such as neodymium or praseodymium other than erbium is added to a part of the optical fiber, operation in the 1.3 μm band becomes possible.

Example 8. With respect to the above-described embodiment, the optical amplifier 11 may be a semiconductor laser type optical amplifier module having optical fibers at both ends as shown in FIG.
In FIG. 16, 117 is a semiconductor laser type optical amplifier in which both end faces of the semiconductor laser are coated with an antireflection film and the reflectance of the end face realized by the oblique end face or the end face window structure is almost zero, and 114 is a current to the semiconductor laser amplifier. Current sources to be supplied, 118a and 118b are lens coupling portions for coupling the input and output of the semiconductor laser type amplifier and the optical fiber, respectively, and 116a and 116b are input and output optical fibers, respectively.

The light input from the optical fiber 116a is guided to the active layer of the semiconductor laser type optical amplifier 117 by the lens coupling section 118a, undergoes optical amplification by the semiconductor laser type optical amplifier, and is output from the semiconductor laser type optical amplifier. Is guided to the output optical fiber 116b by the lens coupling portion 118a.

The single-wavelength optical reflector 52 having the characteristics shown in FIG. 14 (a) is specifically a fiber in which a wavy periodic refractive index change is made in an optical fiber to form a grating reflector. Graying can be used. The variable reflection wavelength at that time is obtained by a change in heat or a change in tension.

Example 9. Optical modulation can also be applied to a Fabry-Perot type resonator having a linear arrangement. FIG. 17 is an overall configuration diagram of another embodiment of the light source device according to the present invention. In the figure, the optical amplifier 11, the optical isolator 12, the periodic wavelength transmission filter 13, the optical fiber 17, the optical intensity modulator 41, the sine wavelength signal generator 42, the optical reflector 51 and the single optical wavelength reflector 52 are all described above. The components are the same as those described in each embodiment.

In this embodiment, the optical amplifier 1 has the same configuration as that of the seventh embodiment.
In this configuration, a light intensity modulator 41 and a sine wave signal generator 42 are inserted between the 1 and the single wavelength light reflector 52. This configuration is applied to a discrete wavelength tunable mode-locked laser. At this time, the operation is similar to that of the third embodiment except that the longitudinal mode wavelength interval is half, that is, fr == c / 2L, and therefore detailed description thereof is omitted.

Example 10. FIG. 18 is an overall configuration diagram of another embodiment of the light source device according to the present invention. In the figure, an optical amplifier 11, an optical isolator 12, a periodic wavelength transmission filter 13, an optical fiber 17, a sine wave signal generator 42, an optical reflector 51 and a single wavelength reflector 52 are the same as the respective constituent elements of the above-mentioned respective embodiments. belongs to.

In this embodiment, the semiconductor laser type amplifier 117 is used as the optical gain means in the ninth embodiment, and the driving current of the semiconductor laser type amplifier is modulated at high speed by the sine wave signal generator 42, whereby the light intensity is modulated. The device 41 and the optical amplifier 11 are combined.

[0064]

As described above, according to the present invention, since the resonator is composed of the multiple wavelength transmission filter, the single wavelength transmission filter and the optical amplifier, it is only necessary to select a desired wavelength from the preset periodic wavelengths. And it has the effect of facilitating control.

As described above, according to the present invention, since the resonator is composed of the plural-wavelength transmission filter, the plurality of single-wavelength transmission filters whose optical paths are separated, and the optical amplifier, the desired wavelength can be selected from the preset periodic wavelengths. It suffices to select a plurality of wavelengths, and the configuration is simple and the control is easy.

Furthermore, since the modulator is used, the control is easy, and furthermore, since the modulator is used, a light source composed of a high-speed optical pulse train can be formed.

Furthermore, since the optical fiber amplifier is used, there is an effect that the assembly precision is not required and the structure is simplified.

Furthermore, since the semiconductor laser amplifier is used, there is an effect that the amplification band is wide and the selection range of the light wavelength can be expanded.

Furthermore, since the modulator is used for the semiconductor laser amplifier, there is an effect that the structure is simplified.

As described above, according to the present invention, since the resonator is composed of the multiple wavelength transmission filter, the single wavelength reflector and the optical amplifier, it is only necessary to select a desired wavelength from the preset periodic wavelengths. There is an effect that control becomes easy.

Furthermore, since the modulator is used, it is easy to control, and it is possible to form a light source composed of a high-speed optical pulse train.

Furthermore, since the optical fiber is used, there is an effect that the assembling precision is not required and the structure is simplified.

Furthermore, since the semiconductor laser amplifier is used, there is an effect that the amplification band is wide and the selection range of the light wavelength can be expanded.

Furthermore, since the modulator is used for the semiconductor laser amplifier, there is an effect that the structure is simplified.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a light source device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of an optical amplifier of the light source device according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating characteristics of a periodic wavelength transmission filter for light and a diagram illustrating a selection operation thereof.

FIG. 4 is a configuration diagram of a light source device according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram of another light source device according to the second embodiment of the present invention.

FIG. 6 is an explanatory diagram of a Mach-Zehnder interferometer according to the second embodiment of the present invention.

FIG. 7 is a transmission characteristic diagram of the Mach-Zehnder interferometer in the second embodiment.

FIG. 8 is a configuration diagram of a light source device according to a third embodiment of the present invention.

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

FIG. 10 is a diagram showing a configuration of an optical amplifier according to a fifth embodiment of the present invention.

FIG. 11 is a configuration diagram of a light source device according to a sixth embodiment of the present invention.

FIG. 12 is a diagram showing a configuration of a semiconductor laser type optical amplifier and an optical modulator in a light source device of Example 6 of the invention.

FIG. 13 is a configuration diagram of a light source device according to a seventh embodiment of the present invention.

FIG. 14 is a diagram for explaining the characteristics and selection operation of the single light wavelength reflector in the seventh embodiment.

FIG. 15 is a configuration diagram of an optical amplifier according to a seventh embodiment of the present invention.

FIG. 16 is a configuration diagram of an optical amplifier according to an eighth embodiment.

FIG. 17 is a configuration diagram of a light source device according to a ninth embodiment of the present invention.

FIG. 18 is a configuration diagram of a light source device according to embodiment 10 of the present invention.

FIG. 19 is a configuration diagram illustrating an operation of a frequency interval control device in a conventional light source device.

FIG. 20 is a diagram showing a configuration of a light source device that is variable in wavelength with a single wavelength in a conventional light source device.

[Explanation of symbols]

11 means having optical gain (optical amplifier), 12 optical isolator, 13 means having periodic transmission characteristic for optical wavelength (periodic wavelength transmission filter), 14, 14a, 14
b means having a single transmission characteristic for the light wavelength (single wavelength transmission filter), 15 optical couplers, 16 polarization controllers, 17 optical fibers, 111 rare earth-doped optical fibers, 112 multiplexers, 113 pump laser diodes , 114 current source, 115a, 115b optical isolator, 116 optical fiber, 117 semiconductor laser type optical amplifier, 118a, 118b lens coupling part, 21 optical brancher, 22a, 22b optical attenuator, 31 Mach-Zehnder interferometer, 311 Mach-Zehnder interferometer Optical input port, 312, 313 Mach-Zehnder interferometer optical output port, 314 optical fiber, 315 optical coupler, 41
Light intensity modulator, 42 sinusoidal signal generator, 51 light reflector, 52 single light wavelength reflector.

Claims (11)

[Claims] 1. A multi-wavelength transmission filter having a characteristic of transmitting at a plurality of preset wavelengths and blocking at another wavelength, and a single wavelength having a characteristic of selectively transmitting one of the transmission wavelengths. A transmission filter, a multi-wavelength transmission filter and a single wavelength transmission filter, a ring resonator is formed by a ring-shaped optical path including an optical amplifier, and a light source is selected at a wavelength selected by the single wavelength transmission filter. Variable wavelength light source device to generate. 2. A multi-wavelength transmission filter having a characteristic of transmitting at a plurality of preset wavelengths and blocking at another wavelength, and a single wavelength having a characteristic of selectively transmitting one of the transmission wavelengths. A ring resonator is formed by a plurality of transmission filters, the plurality of wavelength transmission filters, and the single wavelength transmission filter in each of the branched optical paths, and a ring-shaped optical path further including an optical amplifier. A variable wavelength light source device for generating a light source at a selected wavelength of a plurality of the single wavelength transmission filters. 3. Still further comprising an optical modulator in the ring,
The light source output is a light modulation output.
Alternatively, the variable wavelength light source device according to claim 2. 4. The variable wavelength light source device according to claim 1, wherein the optical amplifier is an optical amplifier using an optical fiber doped with rare earth ions. 5. The variable wavelength light source device according to claim 1 or 2, wherein the optical amplifier is a semiconductor laser amplifier. 6. The variable wavelength light source device according to claim 5, wherein the semiconductor laser amplifier includes a drive current modulator, and modulates the drive current of the semiconductor laser amplifier. 7. A multi-wavelength transmission filter having a property of transmitting at a plurality of preset wavelengths and blocking at other wavelengths, and a property of selectively reflecting one wavelength of the transmission wavelengths and partially transmitting it. A single wavelength reflector having a single wavelength reflector, the multiple wavelength transmission filter and the single wavelength reflector, and a Fabry-Perot resonator formed by a straight optical path including an optical amplifier and a reflector. Tunable light source device that generates a light source at the selected wavelength of the container. 8. The wavelength tunable light source device according to claim 7, further comprising an optical modulator in the linear optical path, wherein the light source output is an optical modulation output. 9. The variable wavelength light source device according to claim 7, wherein the optical amplifier is an optical amplifier using an optical fiber doped with rare earth ions. 10. The variable wavelength light source device according to claim 7, wherein the optical amplifier is a semiconductor laser amplifier. 11. The variable wavelength light source device according to claim 10, wherein the semiconductor laser amplifier includes a drive current modulator, and modulates the drive current of the semiconductor laser amplifier.