JP2014220600A - High-speed wavelength change monitor and light shield device employing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-speed wavelength change monitor for instantaneously detecting a wavelength change with respect to light of any arbitrary wavelength outputted from a wavelength variable laser, and a light shield device for instantaneously shielding output light while using the high-speed wavelength change monitor.SOLUTION: Monitor light 1 is branched from transmission light inputted from a light source 200 by a first optical splitter 101, and monitor light 2 is further branched from the transmission light by a second optical splitter 102. The monitor light 1 branched by the first optical splitter 101 is delayed for T1 sec by an optical retarder 103, and the delayed monitor light 1 and the monitor light 2 are multiplexed by an optical multiplexer 104. A differential frequency electric signal between the delayed monitor light 1 and the monitor light 2 which are multiplexed is generated by a photo mixer 105 and inputted to a high-pass filter 106 which selectively transmits a frequency band equal to or higher than a frequency F in the differential frequency electric signal. A strength of the electric signal transmitted through the high-pass filter 106 is detected by a detector 107, and a wavelength change of the transmission light is detected from a strength change of the electric signal.

Description

  The present invention relates to a high-speed wavelength change monitor that detects a wavelength change of a laser light source in a short time and a light blocking device that blocks a light output path using a wavelength change detection signal from the high-speed wavelength change monitor.

  In the current optical communication, a so-called wavelength path method is adopted in which the wavelength of an optical signal is fixed for a long period of time, thereby forming a wavelength path between specific nodes and performing communication for a long period of time. In the wavelength path method, when it becomes necessary to reconstruct a wavelength path in the event of a failure in an optical communication network or to add a wavelength path to cope with sudden increases in traffic, the wavelength of the optical signal can be changed. It corresponds to.

  In the wavelength path system, a tunable laser is used to change the wavelength of the optical signal. As the wavelength tunable light source, a semiconductor wavelength tunable laser that is small and capable of changing the wavelength with a small amount of power is generally used.

  The operating principle of the semiconductor wavelength tunable laser is as follows. That is, the refractive index of a part or the whole of the resonator of the semiconductor laser is changed by temperature or current to selectively limit the wavelengths that can exist in the resonator. As a structure that causes a wide range of wavelength changes, a super-periodic structure diffraction grating distributed diffraction laser (Non-patent Document 1) and the like have been developed. This superperiodic structure grating distributed diffractive laser is designed so that discrete wavelengths, called so-called longitudinal modes, arranged at regular intervals can exist in the resonator, and one of these wavelengths is selectively selected. The laser oscillation is performed at a single wavelength by amplification. It has been reported that this method oscillates at an arbitrary wavelength in a wavelength region of 100 nm or more.

  However, a wavelength tunable laser using a longitudinal mode, such as a super-periodic structure diffraction grating distributed diffraction laser, has the advantage that the wavelength changes with a small amount of operation. In spite of such changes, there is a drawback that unintended wavelength changes are likely to occur. For this reason, the wavelength monitor device always needs to have a function of monitoring the wavelength change and blocking the output light when the unintended wavelength change occurs.

  The conventional wavelength monitor device calculates the wavelength based on the magnitude of the electrical signal by changing the intensity of the light transmitted through the optical filter into an electrical signal with a photodetector. When monitoring a laser that always outputs a constant wavelength, it is only necessary to detect a change in wavelength from the fixed wavelength, so that signal processing can be performed at high speed using an analog circuit or the like.

N. Fujiwara, et al., “140-nm Quasi-Continuous Fast Sweep Using SSG-DBR Lasers,” IEEE Photonics Technology Letters, 2008, Volume 20, Issue 12, p.1015-1017

  However, when monitoring a wavelength tunable laser with a conventional wavelength monitor device, when a wavelength change occurs from an arbitrary wavelength, four arithmetic operations for detecting the wavelength change as the magnitude of an electric signal, etc. Since the digital signal processing is necessary, the time required for the digital signal processing takes several microseconds or more, and there is a problem that the output light cannot be interrupted instantaneously.

  Accordingly, the present invention has been made in view of such problems, and an object thereof is to provide a high-speed wavelength change monitor that instantaneously detects a wavelength change with respect to light having an arbitrary wavelength output from a wavelength tunable laser. And Another object of the present invention is to provide a light blocking device that instantaneously blocks output light using this high-speed wavelength change monitor.

  In order to solve the above problems, the present invention is an apparatus for monitoring a wavelength change of a laser light source, and includes a first optical branching device that branches light to be measured into at least a first path and a second path, , A second optical branching device that further branches the second route into a third route and a fourth route, a first optical delay device installed on the first route, the first and An optical multiplexer having at least two input ports connected to the third path and at least one output port, and a photo having an optical input port connected to the output port of the optical multiplexer and a difference frequency electric signal output port A mixer, a high-pass filter having a difference frequency electric signal output port connected to the difference frequency electric signal output port of the photomixer, and an electric input connected to the difference frequency electric signal output port of the high pass filter. A detector having a port and a detection signal output, characterized by comprising a.

  According to a second aspect of the present invention, there is provided a device for monitoring a wavelength change of a laser light source, the first optical branching device for branching measured light into at least a first path and a second path, and the second A second optical branching device that further branches the first path into a third path and a fourth path, a first optical delay device installed on the third path, and the first and third paths An optical multiplexer having at least two input ports and at least one output port connected to each other, a photomixer having an optical input port to which the output port of the optical multiplexer is connected, and a difference frequency electrical signal output port, and A high-pass filter having a difference frequency electric signal output port connected to a difference frequency electric signal output port of the photomixer, an electric input port connected to the difference frequency electric signal output port of the high pass filter, and detection Characterized in that and a detector having a signal output.

  According to a third aspect of the present invention, there is provided a device for monitoring a change in wavelength of a laser light source, wherein the first optical branching device branches the measured light into at least a first path and a second path, and the second A second optical branching device that further branches the first path into a third path and a fourth path, a first optical delay device installed on the first path, and the first and third paths An optical multiplexer having at least two input ports and at least one output port connected to each other, a photomixer having an optical input port to which the output port of the optical multiplexer is connected, and a difference frequency electrical signal output port, and A low-pass filter having a difference frequency electric signal output port connected to a difference frequency electric signal output port of the photomixer, an electric input port connected to the difference frequency electric signal output port of the low pass filter, and detection Characterized in that and a detector having a signal output.

  According to a fourth aspect of the present invention, there is provided a device for monitoring a wavelength change of a laser light source, wherein the first optical branching device branches the measured light into at least a first path and a second path, and the second A second optical branching device that further branches the first path into a third path and a fourth path, a first optical delay device installed on the third path, and the first and third paths An optical multiplexer having at least two input ports and at least one output port connected to each other, a photomixer having an optical input port to which the output port of the optical multiplexer is connected, and a difference frequency electrical signal output port, and A low-pass filter having a difference frequency electric signal output port connected to a difference frequency electric signal output port of the photomixer, an electric input port connected to the difference frequency electric signal output port of the low pass filter, and detection Characterized in that and a detector having a signal output.

  The invention according to claim 5 is an optical blocking device that detects a wavelength change of transmission light of a laser light source and blocks the transmission light, and the high-speed wavelength change monitoring device according to claim 1, Based on the second optical delay device to which the transmission light output from the high-speed wavelength change monitor device is input and the detection signal output from the high-speed wavelength change monitor device, the second optical delay device has output from the second optical delay device And an optical shutter that blocks the transmission light.

  According to the high-speed wavelength change monitor of the present invention, a wavelength change from an arbitrary wavelength can be detected instantaneously, and the output optical path of the wavelength tunable laser can be blocked by an optical shutter based on the detected wavelength change. Therefore, a highly reliable laser light source system that does not transmit light of an unintended wavelength can be realized.

It is a figure which shows the structure of the high-speed wavelength change monitor which concerns on one Embodiment of this invention. (A) is a figure which shows the time change of the optical frequency of the monitor light 2, (b) is a figure which shows the time change of the optical frequency of the monitor light 1 after an optical delay device, (c) is detected with a detector. It is a figure which shows the change of the intensity | strength of the electric signal to be performed. It is a figure which shows the structure of the high-speed wavelength change monitor which concerns on one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail.

(Embodiment 1)
FIG. 1 shows the configuration of a high-speed wavelength change monitor according to an embodiment of the present invention. As shown in FIG. 1, the high-speed wavelength change monitor 100 branches the monitor light 1 from the transmission light input from the light source 200 by the first optical branching device 101, and the second stage after the first optical branching device 101. The second optical splitter 102 further splits the monitor light 2 from the transmitted light. The monitor light 1 branched by the first optical splitter 101 is delayed by T1 seconds by the optical delay device 103, and the delayed monitor light 1 and the monitor light 2 branched by the second optical splitter 102 are optical multiplexers. Combine at 104. A high-pass that selectively generates a difference frequency electric signal between the combined delayed monitor light 1 and the monitor light 2 by the photomixer 105 and selectively transmits a frequency band equal to or higher than the frequency F that is a high frequency component of the difference frequency electric signal. Input to the filter 106. The detector 107 detects the intensity of the electrical signal that has passed through the high-pass filter 106, and detects the change in the wavelength of the transmitted light emitted from the light source 200 from the change in the intensity of the electrical signal.

  Here, as an example, the optical delay device 103 delays the input monitor light 1 by about 100 nanoseconds, and sets the transmission frequency band of the high-pass filter 106 to 1 GHz or more.

  In this case, the optical multiplexer 104 receives the monitor light 2 that is a part of the light emitted from the current light source and the monitor light 1 that is a part of the light emitted from the light source 100 nanoseconds before. The photomixer 105 generates a beat signal that is a difference frequency electrical signal between the monitor light 1 and the monitor light 2. That is, an electrical signal having a frequency difference between the current optical frequency of the light source and the optical frequency about 100 nanoseconds before is generated.

  Since the high-pass filter 106 transmits high-frequency components, when the frequency difference between the monitor light 1 and the monitor light 2 is large, that is, when the mutual wavelength difference is large, the high-frequency filter generated by the phomixer 105 is transmitted by the high-pass filter 106. . For this reason, the intensity of the electric signal passing through the high-pass filter 106 increases, and as a result, the electric signal intensity detected by the detector 107 increases. When the transmission frequency band of the high-pass filter is set to 1 GHz or more as in the present embodiment, the optical frequency difference between the monitor light 1 and the monitor light 2 when the wavelength of the light source 200, that is, the optical frequency changes by 1 GHz or more within 100 nanoseconds. Exceeds 1 GHz. When the optical frequency difference exceeds 1 GHz as described above, an electric signal having a frequency of 1 GHz or more is generated by the photomixer 105, and these signals pass through the high-pass filter 106 and are input to the detector 107. By detecting an increase in the electrical signal detected by the detector 107, it is possible to detect that a wavelength change has occurred in the light source 200.

  FIG. 2 (a) shows the time change of the optical frequency of the monitor light 2, FIG. 2 (b) shows the time change of the optical frequency of the monitor light 1 after the optical delay device 103, and FIG. The change in the intensity of the electrical signal is illustrated. Here, the optical frequency of the monitor light 2 changes at time t1, and accordingly, the optical frequency of the monitor light 1 after the delay device 103 changes at time t2 after about 100 nanoseconds. Since the optical frequencies of the monitor light 2 and the monitor light 1 after the delay device 103 are different between the times t1 and t2, an electric signal having a frequency of 1 GHz or more is generated in this time zone (t1 to t2). Since the electric signal generated here passes through the high-pass filter 106, the intensity of the electric signal detected by the detector 107 increases, and it can be detected that the optical frequency has changed.

  In the high-speed wavelength change monitor shown in FIG. 1, the monitor light 1 is delayed by the optical delay unit 103, but the optical delay unit 103 installed between the optical branching unit 101 and the optical multiplexer 104 is optically branched. The monitor light 2 may be delayed instead of being installed between the optical device 102 and the optical multiplexer 104 to delay the monitor light 1.

(Embodiment 2)
FIG. 3 shows the configuration of a high-speed wavelength change monitor according to an embodiment of the present invention. As shown in FIG. 3, the light blocking device includes a light source 200, the wavelength change monitoring device described in the first embodiment, an optical delay device 301 that delays transmission light for T2 seconds, and an optical signal after receiving an electrical signal. The optical shutter 302 has an operation time of T3 seconds until it is shut off.

  Here, as an example, it is assumed that the optical delay device 301 delays the input transmission light by about 1 microsecond, and the optical shutter 302 receives the wavelength change detection signal transmitted from the wavelength change monitor device until the light is cut off. Is set to about 500 nanoseconds (0.5 microseconds).

  In this case, since the transmission light is delayed by 1 microsecond by the optical delay device 301, the light is blocked before the transmission light whose wavelength has changed reaches the optical shutter 302. As a result, it is possible to prevent the transmission light after the wavelength change from being output.

  As mentioned above, although embodiment of this invention was explained in full detail, the concrete structure is not restricted to each embodiment, The design change etc. of the range which does not deviate from the summary of this invention are included.

  In the high-speed wavelength change monitor and the light blocking device according to the present embodiment, an example in which an increase in the intensity of the transmitted electric signal is detected using a high-pass filter is shown. Operation may be performed by detecting a decrease in signal.

DESCRIPTION OF SYMBOLS 100 High-speed wavelength change monitor 101,102 Optical branching device 103,301 Optical delay device 104 Optical multiplexer 105 Photomixer 106 High pass filter 107 Detector 200 Light source 302 Optical shutter

Claims (5)

An apparatus for monitoring the wavelength change of a laser light source,
A first optical branching device for branching measured light into at least a first path and a second path;
A second optical branching device that further branches the second route into a third route and a fourth route;
A first optical delay device installed on the first path;
An optical multiplexer having at least two input ports and at least one output port to which the first and third paths are connected;
A photomixer having an optical input port to which an output port of the optical multiplexer is connected and a differential frequency electric signal output port;
A high-pass filter having an electrical input port to which the difference frequency electrical signal output port of the photomixer is connected and a difference frequency electrical signal output port;
An electrical input port to which the difference frequency electrical signal output port of the high pass filter is connected and a detector having a detection signal output;
A high-speed wavelength change monitor device comprising: An apparatus for monitoring the wavelength change of a laser light source,
A first optical branching device for branching measured light into at least a first path and a second path;
A second optical branching device that further branches the second route into a third route and a fourth route;
A first optical delay device installed on the third path;
An optical multiplexer having at least two input ports and at least one output port to which the first and third paths are connected;
A photomixer having an optical input port to which an output port of the optical multiplexer is connected and a differential frequency electric signal output port;
A high-pass filter having an electrical input port to which the difference frequency electrical signal output port of the photomixer is connected and a difference frequency electrical signal output port;
An electrical input port to which the difference frequency electrical signal output port of the high pass filter is connected and a detector having a detection signal output;
A high-speed wavelength change monitor device comprising: An apparatus for monitoring the wavelength change of a laser light source,
A first optical branching device for branching measured light into at least a first path and a second path;
A second optical branching device that further branches the second route into a third route and a fourth route;
A first optical delay device installed on the first path;
An optical multiplexer having at least two input ports and at least one output port to which the first and third paths are connected;
A photomixer having an optical input port to which an output port of the optical multiplexer is connected and a differential frequency electric signal output port;
A low-pass filter having an electrical input port to which the difference frequency electrical signal output port of the photomixer is connected and a difference frequency electrical signal output port;
An electrical input port to which the difference frequency electrical signal output port of the low-pass filter is connected and a detector having a detection signal output;
A high-speed wavelength change monitor device comprising: An apparatus for monitoring the wavelength change of a laser light source,
A first optical branching device for branching measured light into at least a first path and a second path;
A second optical branching device that further branches the second route into a third route and a fourth route;
A first optical delay device installed on the third path;
An optical multiplexer having at least two input ports and at least one output port to which the first and third paths are connected;
A photomixer having an optical input port to which an output port of the optical multiplexer is connected and a differential frequency electric signal output port;
A low-pass filter having an electrical input port to which the difference frequency electrical signal output port of the photomixer is connected and a difference frequency electrical signal output port;
An electrical input port to which the difference frequency electrical signal output port of the low-pass filter is connected and a detector having a detection signal output;
A high-speed wavelength change monitor device comprising: A light blocking device that detects a wavelength change of transmission light of a laser light source and blocks the transmission light,
The high-speed wavelength change monitoring device according to claim 1,
A second optical delay device to which the transmission light output from the high-speed wavelength change monitoring device is input;
An optical shutter that blocks the transmission light output from the second optical delay device based on the detection signal output from the high-speed wavelength change monitoring device;
A light shielding device comprising:

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