CN117638614A - Device and method for generating broadband optical frequency comb with adjustable center wavelength - Google Patents

Abstract

The invention discloses a device and a method for generating a broadband optical frequency comb with an adjustable center wavelength, and relates to the technical field of optics. The device of the invention superimposes a sinusoidal modulation signal with the frequency of 1.6GHz generated by a microwave frequency synthesizer with direct current bias through a T-shaped bias device and loads the sinusoidal modulation signal onto a weak resonant cavity Fabry-Perot laser, so that the laser presents a gain switch state. And then the continuous optical signal output by the first tunable laser source is unidirectionally injected into the gain-switching weak resonant cavity Fabry-Perot laser, so that the laser outputs an optical frequency comb signal with the central wavelength capable of being tuned in a large range and the bandwidth periodically changing along with the increase of the wavelength of the injected optical signal. In order to further improve the performance of the optical frequency comb, a second tunable laser source is additionally introduced, and double light is injected into the laser, so that an optical frequency comb signal with larger bandwidth and adjustable central wavelength in a large range can be obtained compared with single light injection. The invention is suitable for the fields of measurement, spectroscopy, optical communication, microwave photonics and the like.

Description

Device and method for generating broadband optical frequency comb with adjustable center wavelength

Technical Field

The invention relates to the technical field of optics, in particular to a device and a method for generating a broadband optical frequency comb with an adjustable center wavelength.

Background

An optical frequency comb (optical frequency comb, OFC) is a special laser source whose time sequence is a series of narrow pulses whose spectrum then exhibits a series of discrete, equally spaced, strongly coherent comb lines. The OFC effectively establishes the connection between the optical frequency and the microwave frequency, and promotes the development of various fields such as precise metering, microwave photon, optical fiber communication, radar detection and the like. Since OFC was first generated based on mode-locking technology in 2000, various generation schemes based on microcavities, electro-optic modulators, semiconductor lasers, etc. have been reported. The scheme of obtaining the OFC under the light injection based on the gain switch semiconductor laser is attracting attention because of the advantages of simple system structure, low cost, integration, flexible and adjustable comb tooth space of the generated OFC and the like.

The gain switch is a state of the semiconductor laser under the direct modulation of a large signal, and the introduction of the injected light establishes the correlation between output pulses in the state, so that the OFC with high quality can be generated. In recent years, many developments have been made in the related studies based on this scheme, but the lasers used have been mainly focused on single longitudinal mode lasers such as distributed feedback semiconductor lasers, vertical cavity surface emitting lasers, and the like. Since these single longitudinal mode lasers generally output only one lasing wavelength, and the tunable range of the lasing wavelength is very limited, it is difficult to obtain a wide-spectrum OFC with a widely tunable center wavelength. Based on this, in order to meet the requirements of some special application fields on wide-spectrum OFCs with adjustable center wavelengths in a large range, it is necessary to invent a device and a method for generating broadband optical frequency combs with adjustable center wavelengths.

Disclosure of Invention

The invention aims to solve the technical problem that the generation device of the broadband optical frequency comb with the adjustable center wavelength is designed for overcoming the defects in the prior art, and the broadband optical frequency comb with the adjustable center wavelength in a large range can be generated.

In order to achieve the above purpose, the present invention provides the following technical solutions: the device for generating the broadband optical frequency comb with the adjustable center wavelength comprises a weak resonant cavity Fabry-Perot laser 600, a direct modulation module 700, a tunable laser source 100, a tunable laser source 200, a light injection module 300, an optical circulator 400 and an optical frequency comb detection module 500;

the weak resonant cavity fabry-perot laser 600 is a multi-longitudinal mode laser, which can simultaneously laser a plurality of longitudinal modes during free running, and is used for generating optical frequency comb signals with a large-range tuning center wavelength;

the direct modulation module 700 is configured to output a high-power sinusoidal current signal with a frequency of 1.6GHz and a power of 19 dBm, and after the sinusoidal signal and the dc bias are superimposed by a T-shaped bias, perform current modulation on the weak resonant cavity fabry-perot laser 600, and drive the weak resonant cavity fabry-perot laser 600 to present a gain switching state, where the direct modulation module 700 is connected with the weak resonant cavity fabry-perot laser 600;

the tunable laser sources 100 and 200 are used for providing continuous optical signals;

the optical injection module 300 is used for injecting continuous optical signals output by the tunable laser sources 100 and 200 into the optical circulator 400, and the optical injection module 300 is connected with the tunable laser sources 100 and 200 and the optical circulator 400;

the optical circulator 400 is configured to inject a continuous optical signal into the weak resonator fabry-perot laser 600, and send an optical frequency comb signal output by the weak resonator fabry-perot laser 600 to the optical frequency comb detection module 500, where the optical circulator 400 is connected to the optical injection module 300, the optical frequency comb detection module 500, and the weak resonator fabry-perot laser 600, respectively;

the optical frequency comb detection module 500 is used for detecting the optical frequency comb performance output by the weak cavity fabry-perot laser 600, and the optical frequency comb detection module 500 is connected with the optical circulator 400.

Optionally, the direct modulation module 700 includes a microwave frequency synthesizer 701, a dc power supply 702, and a T-bias 703;

the microwave frequency synthesizer 701 is configured to output sinusoidal current with adjustable frequency fm and adjustable power Pm;

the dc power supply 702 is used to provide dc bias current required by the laser;

the T-type bias 703 is configured to couple the sinusoidal current and the dc bias current into one path, and then load the sinusoidal current and the dc bias current onto the working current of the weak cavity fp ld 600, so that the weak cavity fp ld 600 presents a gain switching state.

Optionally, the light injection module 300 includes a first light attenuator 301, a first polarization controller 302, a first optical coupler 303, a second light attenuator 304, a second polarization controller 305, a second optical coupler 306, a third optical coupler 308, a first optical power meter 307, and a second optical power meter 309;

the first optical attenuator 301 is used for adjusting the magnitude of continuous optical power output by the tunable laser source 100, wherein the first optical attenuator 301 is connected with the tunable laser source 100 and the first polarization controller 302;

the second optical attenuator 304 is used for adjusting the magnitude of the continuous optical power output by the tunable laser source 200, wherein the second optical attenuator 304 is connected with the tunable laser source 200 and the second polarization controller 305;

the first polarization controller 302 is configured to adjust a polarization state of an optical signal output by the tunable laser source 100, where the first polarization controller 302 is connected to the first optical attenuator 301 and the first optical coupler 303;

the second polarization controller 305 is configured to adjust a polarization state of the optical signal output by the tunable laser source 200, where the second polarization controller 305 is connected to the second optical attenuator 304 and the second optical coupler 306;

the first optical coupler 303 is configured to divide the continuous light output by the tunable laser source 100 into two parts during single light injection, wherein a part of the continuous light enters the first optical power meter 307, and is used to measure the optical power of the first injected light, and another part of the continuous light is unidirectionally injected into the weak cavity fabry-perot laser 600 after passing through the third optical coupler 308 and the optical circulator 400, so as to drive the weak cavity fabry-perot laser 600 in a gain switching state to generate an optical frequency comb with an adjustable center wavelength, where the first optical coupler 303 is respectively connected to the first polarization controller 302, the first optical power meter 307 and the third optical coupler 308;

the second optical coupler 306 is configured to divide the continuous light output by the tunable laser source 200 into two parts during the dual-light injection, wherein a part of the continuous light enters the second optical power meter 309 for measuring the optical power of the second injected light, and another part of the continuous light is coupled with a part of the continuous light output by the tunable laser source 100 at the third optical coupler 308, where the second optical coupler 306 is connected to the second polarization controller 305, the second optical power meter 309 and the third optical coupler 308, respectively;

the third optical coupler 308 is configured to couple a part of light output by each of the tunable laser source 100 and the tunable laser source 200 into a whole at the third optical coupler 308 during the dual-optical injection, and then unidirectionally inject the light into the weak resonant cavity fabry-perot laser 600 after passing through the optical circulator 400, so as to drive the weak resonant cavity fabry-perot laser 600 to generate an optimized optical frequency comb;

optionally, the optical frequency comb detection module 500 includes a fourth optical coupler 501, a spectrum analyzer 502, a fifth optical coupler 503, a first photodetector 504, a second photodetector 505, a spectrum analyzer 506, and a digital oscilloscope 507, which are sequentially connected;

the optical signal output from the optical circulator 400 enters the fourth optical coupler 501 to be split, one part of the split optical signal enters the spectrum analyzer 502 to be subjected to spectrum measurement, the other part of the split optical signal enters the fifth optical coupler 503 to be split again, one part of the split optical signal is converted into an electric signal by the first photoelectric detector 504 through the fifth optical coupler 503 and then is input into the spectrum analyzer 506 to observe a frequency spectrum, and the other part of the split optical signal is converted into an electric signal by the second photoelectric detector 505 and then is input into the digital oscilloscope 507 to be subjected to time series measurement.

A method for generating a broadband optical frequency comb with adjustable center wavelength is used for any one of the above steps as follows:

step one: the microwave frequency synthesizer 701 outputs a sinusoidal modulation signal with the frequency of 1.6GHz and the power of 19 dBm, and the sinusoidal modulation signal and the direct current output by the direct current power supply 702 are superimposed through the T-shaped bias device 703 and then are loaded onto the working current of the weak resonant cavity Fabry-Perot laser 600 together, so that the weak resonant cavity Fabry-Perot laser 600 presents a gain switching state;

step two: the tunable laser source 100 outputs a continuous optical signal with adjustable wavelength and power, the continuous optical signal is divided into two parts after passing through the first optical attenuator 301, the first polarization controller 302 and the first optical coupler 303, and one part (such as 10%) enters the first optical power meter 307 to monitor the injection power;

step three: another part (for example, 90%) of the output from the first optical coupler 303 is injected into the weak cavity fabry-perot laser 600 in a unidirectional manner after passing through the third optical coupler 308 and the optical circulator 400, so that the weak cavity fabry-perot laser 600 in a gain switching state is driven to generate an optical frequency comb with a center wavelength which is adjustable in a large range and a bandwidth which is periodically changed between 30.4 GHz and 76.8 GHz along with the increase of the wavelength of the injected light;

step four: in order to further improve the optical frequency comb performance generated by the single light injection corresponding to the first to third steps, the second tunable laser source 200 is additionally introduced, and the dual light injection is adopted to the weak resonant cavity fabry-perot laser 600 in the gain switch state, so that the optical frequency comb signal with larger bandwidth and adjustable central wavelength in a large range can be obtained compared with the single light injection. During dual light injection, the continuous light signal output by the second tunable laser source 200 is divided into two parts after passing through the second optical attenuator 304, the second polarization controller 305 and the second optical coupler 306, wherein one part (such as 10%) enters the second optical power meter 309 to monitor the magnitude of the second beam injection light power;

step five: another portion (e.g., 90%) of the light output from the second optical coupler 306 and a portion (e.g., 90%) of the light output from the first optical coupler 303 are coupled into one path by the third optical coupler 308, and then are double-optically injected into the fabry-perot laser 600 with a weak resonant cavity by the optical circulator 400, and when the two injected lights are located between the two modes of the laser 600 and the wavelength difference between the two injected lights is about twice the mode spacing (about 0.28 nm) of the laser 600, a high-quality optical frequency comb with a bandwidth exceeding 145 GHz and an adjustable center wavelength can be obtained, and the high-quality frequency comb signal can be observed from the detection module 500.

Optionally, the 10% optical signal output by the first optical coupler 303 in the second step enters the first optical power meter 307;

optionally, the remaining 90% of the optical signals output by the first optical coupler 303 in the third step are unidirectionally injected into the weak cavity fabry-perot laser 600 after passing through the third optical coupler 308 and the optical circulator 400;

optionally, the 10% optical signal output by the second optical coupler 306 in the fourth step enters the second optical power meter 309;

optionally, the remaining 90% of the optical signal output by the second optical coupler 306 in the fifth step and the remaining 90% of the optical signal output by the first optical coupler 303 are combined into a single signal through the third optical coupler 308, and the signal is injected into the weak cavity fabry-perot laser 600 after passing through the optical circulator 400.

Compared with the prior art, the invention has the beneficial effects that:

1. the invention adopts the weak resonant cavity Fabry-Perot laser, and compared with other lasers, the laser has the characteristics of long cavity length, low front end surface reflectivity and the like, and can realize simultaneous lasing of multiple longitudinal modes, high external light injection efficiency and large mode output share.

2. The invention adopts sine current to directly modulate the driving current of the weak resonant cavity Fabry-Perot laser, and the direct modulation structure has the advantages of simple system, low cost, easy realization, convenient tuning and the like, and can realize continuous adjustment of comb pitch by simply changing the frequency of the output signal of the microwave frequency synthesizer.

3. The invention adopts a combined optical comb generating structure with single optical injection and double optical injection. Firstly, generating an optical frequency comb with a central wavelength capable of being tuned in a large range and a bandwidth periodically changing along with the wavelength of injected light between 30.4 GHz and 76.8 GHz through single light injection; then, to expand the bandwidth of the optical comb, double optical injection is further introduced (double optical injection is further introduced to expand the bandwidth of the optical comb), and by selecting matched injection light wavelengths, a high-quality optical frequency comb with a bandwidth exceeding 145 GHz can be obtained.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed for the description of the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of the basic structure of an optical frequency comb generating device according to the present invention;

FIG. 2 is a schematic structural view showing a preferred example of the optical frequency comb generating device of the present invention;

FIG. 3 is a spectral diagram of the output of a single-light injection gain-switch weak cavity Fabry-Perot laser at 6 different injection light wavelengths;

FIG. 4 is a spectral diagram of an optical frequency comb produced by double light injection under optimized conditions.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.

Embodiment one:

referring to fig. 1, a generating device of a broadband optical frequency comb with an adjustable center wavelength is characterized in that: the tunable laser comprises a weak resonant cavity Fabry-Perot laser 600, a direct modulation module 700, a tunable laser source 100, a tunable laser source 200, a light injection module 300, a light circulator 400 and an optical frequency comb detection module 500;

the weak resonant cavity fabry-perot laser 600 is a multi-longitudinal mode laser that can simultaneously lase a number of longitudinal modes during free-running for generating an optical frequency comb signal with a widely tuned center wavelength;

the direct modulation module 700 is configured to output a high-power sinusoidal current signal with a frequency of 1.6GHz and a power of 19 dBm, and after the sinusoidal signal and the direct current bias are superimposed by a T-shaped bias, perform current modulation on the weak resonant cavity fabry-perot laser 600, and drive the weak resonant cavity fabry-perot laser 600 to present a gain switching state, where the direct modulation module 700 is connected with the weak resonant cavity fabry-perot laser 600;

tunable laser sources 100 and 200 for providing a continuous optical signal;

the optical injection module 300 is used for injecting the continuous optical signals output by the tunable laser sources 100 and 200 into the optical circulator 400, and the optical injection module 300 is connected with the tunable laser sources 100 and 200 and the optical circulator 400;

the optical circulator 400 is used for injecting a continuous optical signal into the weak resonator fabry-perot laser 600 and sending an optical frequency comb signal output by the weak resonator fabry-perot laser 600 to the optical frequency comb detection module 500, and the optical circulator 400 is respectively connected with the optical injection module 300, the optical frequency comb detection module 500 and the weak resonator fabry-perot laser 600;

the optical frequency comb detection module 500 is used for detecting the optical frequency comb performance output by the weak cavity fabry-perot laser 600, and the optical frequency comb detection module 500 is connected with the optical circulator 400.

The direct modulation module 700 includes a microwave frequency synthesizer 701, a dc power supply 702, and a T-bias 703; the microwave frequency synthesizer 701 is used for outputting sinusoidal current with adjustable frequency fm and power Pm; the dc power supply 702 is used to provide the dc bias current required by the laser; the T-type bias 703 is configured to couple the sinusoidal current and the dc bias current into one path, and then load the sinusoidal current and the dc bias current onto the working current of the weak cavity fp ld 600, so that the weak cavity fp ld 600 presents a gain switching state.

The light injection module 300 includes a first light attenuator 301, a first polarization controller 302, a first light coupler 303, a second light attenuator 304, a second polarization controller 305, a second light coupler 306, a third light coupler 308, a first light power meter 307, and a second light power meter 309;

the first optical attenuator 301 is used for adjusting the magnitude of continuous optical power output by the tunable laser source 100, wherein the first optical attenuator 301 is connected with the tunable laser source 100 and the first polarization controller 302;

the second optical attenuator 304 is used to adjust the magnitude of the continuous optical power output by the tunable laser source 200, where the second optical attenuator 304 is connected to the tunable laser source 200 and the second polarization controller 305;

the first polarization controller 302 is configured to adjust a polarization state of an optical signal output by the tunable laser source 100, where the first polarization controller 302 is connected to the first optical attenuator 301 and the first optical coupler 303;

a second polarization controller 305 is configured to adjust a polarization state of an optical signal output by the tunable laser source 200, where the second polarization controller 305 is connected to the second optical attenuator 304 and the second optical coupler 306;

the first optical coupler 303 is configured to divide the continuous light output by the tunable laser source 100 into two parts during single light injection, wherein a part of the continuous light enters the first optical power meter 307 for measuring the optical power of the first injected light, and another part of the continuous light is unidirectionally injected into the weak cavity fabry-perot laser 600 after passing through the third optical coupler 308 and the optical circulator 400, so as to drive the weak cavity fabry-perot laser 600 in a gain switching state to generate an optical frequency comb with an adjustable center wavelength, where the first optical coupler 303 is respectively connected to the first polarization controller 302, the first optical power meter 307 and the third optical coupler 308;

a second optical coupler 306 for dividing the continuous light output from the tunable laser source 200 into two parts during the dual-light injection, wherein a part of the continuous light enters a second optical power meter 309 for measuring the optical power of the second injected light, and the other part of the continuous light is coupled with a part of the continuous light output from the tunable laser source 100 at a third optical coupler 308, wherein the second optical coupler 306 is connected to the second polarization controller 305, the second optical power meter 309 and the third optical coupler 308, respectively;

the third optical coupler 308 is configured to couple a part of light output by each of the tunable laser source 100 and the tunable laser source 200 into a whole at the third optical coupler 308 during dual-light injection, and then perform unidirectional injection into the weak cavity fabry-perot laser 600 after passing through the optical circulator 400, so as to drive the weak cavity fabry-perot laser 600 to generate an optimized optical frequency comb;

the optical frequency comb detection module 500 comprises a fourth optical coupler 501, a spectrum analyzer 502, a fifth optical coupler 503, a first photoelectric detector 504, a second photoelectric detector 505, a spectrum analyzer 506 and a digital oscilloscope 507 which are connected in sequence;

the optical signal output from the optical circulator 400 enters the fourth optical coupler 501 to be split, one part of the split optical signal enters the spectrum analyzer 502 to be subjected to spectrum measurement, the other part of the split optical signal enters the fifth optical coupler 503 to be split again, one part of the split optical signal is converted into an electric signal by the first photoelectric detector 504 through the fifth optical coupler 503 and then is input into the spectrum analyzer 506 to observe a frequency spectrum, and the other part of the split optical signal is converted into an electric signal by the second photoelectric detector 505 and then is input into the digital oscilloscope 507 to be subjected to time series measurement.

Embodiment two:

a method for generating a broadband optical frequency comb with adjustable center wavelength adopts the embodiment, and comprises the following steps:

step one: the microwave frequency synthesizer 701 outputs a sinusoidal modulation signal with the frequency of 1.6GHz and the power of 19 dBm, and the sinusoidal modulation signal and the direct current output by the direct current power supply 702 are superimposed through the T-shaped bias device 703 and then are loaded onto the working current of the weak resonant cavity Fabry-Perot laser 600 together, so that the weak resonant cavity Fabry-Perot laser 600 presents a gain switching state;

step two: the tunable laser source 100 outputs a continuous optical signal with adjustable wavelength and power, the continuous optical signal is divided into two parts after passing through the first optical attenuator 301, the first polarization controller 302 and the first optical coupler 303, and one part (such as 10%) enters the first optical power meter 307 to monitor the injection power;

step three: another part (for example, 90%) of the output from the first optical coupler 303 is injected into the weak cavity fabry-perot laser 600 in a unidirectional manner after passing through the third optical coupler 308 and the optical circulator 400, so that the weak cavity fabry-perot laser 600 in a gain switching state is driven to generate an optical frequency comb with a center wavelength which is adjustable in a large range and a bandwidth which is periodically changed between 30.4 GHz and 76.8 GHz along with the increase of the wavelength of the injected light;

step four: in order to further improve the optical frequency comb performance generated by the single light injection corresponding to the first to third steps, the second tunable laser source 200 is additionally introduced, and the dual light injection is adopted to the weak resonant cavity fabry-perot laser 600 in the gain switch state, so that the optical frequency comb signal with larger bandwidth and adjustable central wavelength in a large range can be obtained compared with the single light injection. During dual light injection, the continuous light signal output by the second tunable laser source 200 is divided into two parts after passing through the second optical attenuator 304, the second polarization controller 305 and the second optical coupler 306, wherein one part (such as 10%) enters the second optical power meter 309 to monitor the magnitude of the second beam injection light power;

step five: another portion (e.g., 90%) of the light output from the second optical coupler 306 and a portion (e.g., 90%) of the light output from the first optical coupler 303 are coupled into one path by the third optical coupler 308, and then are double-optically injected into the fabry-perot laser 600 with a weak resonant cavity by the optical circulator 400, and when the two injected lights are located between the two modes of the laser 600 and the wavelength difference between the two injected lights is about twice the mode spacing (about 0.28 nm) of the laser 600, a high-quality optical frequency comb with a bandwidth exceeding 145 GHz and an adjustable center wavelength can be obtained, and the high-quality frequency comb signal can be observed from the detection module 500.

Embodiment III:

referring to fig. 2, there is shown a specific structure of a preferred embodiment of an optical frequency comb generating device according to the present invention, which includes a tunable laser source 100, a tunable laser source 200, a first optical attenuator 301, a first polarization controller 302, a first optical coupler 303, a second optical attenuator 304, a second polarization controller 305, a second optical coupler 306, a first optical power meter 307, a third optical coupler 308, a second optical power meter 309, an optical circulator 400, a weak resonant cavity fabry-perot laser 600, a microwave frequency synthesizer 701, a dc power supply 702, and a T-type bias 703, a fourth optical coupler 501, a spectrum analyzer 502, a fifth optical coupler 503, a first photodetector 504, a second photodetector 505, a spectrum analyzer 506, and a digital oscilloscope 507;

the microwave frequency synthesizer 701 outputs a sinusoidal modulation signal with the frequency of 1.6GHz and the power of 19 dBm, and the sinusoidal modulation signal and the dc bias output by the dc power supply 702 are superimposed by the T-shaped bias 703 and then loaded onto the working current of the weak cavity fabry-perot laser 600 together, so that the weak cavity fabry-perot laser 600 presents a gain switching state. Then, the continuous optical signal output by the tunable laser source 100 is divided into two parts after passing through the first optical attenuator 301, the first polarization controller 302 and the first optical coupler 303, wherein one part (for example, 10%) enters the first optical power meter 307 to monitor the power of single optical injection, and the other part (for example, 90%) is unidirectionally injected into the weak cavity fabry-perot laser 600 after passing through the third optical coupler 308 and the optical circulator 400, and the weak cavity fabry-perot laser 600 in a gain switch state is driven to generate an optical frequency comb with adjustable center wavelength by utilizing the spectrum expansion effect caused by optical injection.

In order to analyze the performance of the optical frequency comb, the signal output by the weak cavity fabry-perot laser 600 is further sent to the optical frequency comb detection module 500 for detection. The signal output from the weak resonator fabry-perot laser 600 enters the fourth optical coupler 501 through the 3 rd port of the optical circulator 400 to be split, one part (for example, 50%) of the split signal enters the spectrum analyzer 502 to be subjected to spectrum measurement, the other part (for example, 50%) enters the fifth optical coupler 503 to be split again, one part (for example, 50%) of the split signal enters the first optical coupler 503 to be converted into an electric signal through the first photoelectric detector 504 and then is input into the spectrum analyzer 506 to be observed, and the other part (for example, 50%) of the split signal is converted into an electric signal through the second photoelectric detector 505 and then is input into the digital oscilloscope 507 to be subjected to time series measurement.

In order to further improve the optical frequency comb performance generated by single light injection, the second tunable laser source 200 is additionally introduced, and double light injection is adopted to the weak resonant cavity fabry-perot laser 600 in the gain switch state, so that an optical frequency comb signal with larger bandwidth and a large-range adjustable center wavelength can be obtained compared with the single light injection. During dual light injection, the continuous light signal output by the second tunable laser source 200 is divided into two parts after passing through the second optical attenuator 304, the second polarization controller 305 and the second optical coupler 306, wherein one part (such as 10%) enters the optical power meter 309 to monitor the magnitude of the second beam of injected light power; a further part (e.g. 90%) of the light (e.g. 90%) output by the first optical coupler 303 is coupled into one path by the third optical coupler 308, and then is injected into the weak cavity fabry-perot laser 600 by the optical circulator 400, under the optimized double-light injection condition, a high-quality optical frequency comb with a bandwidth exceeding 145 GHz and adjustable center wavelength can be obtained, and the high-quality frequency comb signal can be observed from the optical frequency comb detection module 500.

In this embodiment, in the implementation, the following devices may be used in each part of the apparatus, and other types and components with similar functions may also be used, where the weak cavity fabry-perot laser 600 uses a laser that is excited by multiple longitudinal modes at the same time; the tunable laser source 100 employs a tunable laser of Santec TSL-570; the tunable laser source 200 employs a tunable laser of Santec TSL-710; all optical attenuators adopt 1550 nm wavelength adjustable optical attenuators; all polarization controllers are common commercial polarization controllers; the first beam splitter 303 and the second beam splitter 306 use 10:90 fiber couplers; the third beam splitter 308, the fourth beam splitter 501 and the fifth beam splitter 503 employ 50:50 fiber couplers; all the optical power meters adopt S155C optical fiber power sensors with PM100D meter heads; the optical circulator 400 adopts a three-port optical circulator; the microwave frequency synthesizer 701 adopts an Agilent E8257C type analog signal generator, the frequency range of which is adjustable from 250 kHz to 20 GHz, and the power range of which is adjustable from-135 dBm to 25 dBm; the direct current power supply 702 adopts a temperature current controller LDC-3908; the T-type bias 703 employs a common commercial bias; the first photodetector 504 employs a U2T-XPDV2150R photodetector with a 50 GHz bandwidth; the second photodetector 505 employs a New Focus 1544-B photodetector with a bandwidth of 12 GHz; the spectrum analyzer 502 adopts a Aragon Photonics BOSA lite + spectrum analyzer with 20 MHz resolution; the spectrum analyzer 506 employs a Rohde & Schwarz FSW67 spectrum analyzer with 67 GHz bandwidth; the digital oscilloscope 507 employs an Agilent X91604a digital oscilloscope with a 16 GHz bandwidth.

Embodiment four:

the invention is further illustrated by the combination of the above examples;

please refer to fig. 3 and fig. 4. Wherein FIG. 3 shows the injection optical powerP _inj When= 3.397 μw, different wavelengths of injected lightλ _inj And then, a single light injection gain switch is used for switching a spectrum graph output by the weak resonant cavity Fabry-Perot laser. FIG. 4 is a spectral diagram of an optical frequency comb produced by double light injection under optimized conditions. In order to facilitate understanding of the technical scheme of the invention, the following relevant parameters are selected as examples for analysis and explanation.

In this embodiment, the current and temperature of the weak cavity fabry-perot laser 600 are controlled by a high-precision low-noise laser controller, the control precision of the current is 0.01 mA, and the control precision of the temperature is 0.01 ℃. In the implementation process, the temperature of the weak cavity fabry-perot laser 600 is stabilized at 17.00 ℃, the current is stabilized at 52.00 mA, the output power of the free-running weak cavity fabry-perot laser 600 is about 0.447 mW under the above temperature and current conditions, the spectral range is about 1532 nm-1552 nm, and the interval between two adjacent modes is about 0.28 nm (35.0 GHz).

FIG. 3 shows the injection optical powerP _inj When= 3.397 μw, 6 different wavelengths of injection lightλ _inj And then, a single light injection gain switch is used for switching a spectrum graph output by the weak resonant cavity Fabry-Perot laser. Wherein the black arrows indicate the positions of the wavelengths of the injected light, and the wavelengths of the injected light correspond to FIGS. 3 (a) -3 (f)λ _inj 1545.3822 nm (a), 1545.6522 nm (b), 1545.7622 nm (c), 1545.8472 nm (d), 1545.8672 nm (e), and1545.9272 nm (f). As can be seen from fig. 3, tuning of the center wavelength of the optical frequency comb is easily achieved by varying the wavelength of the injected light. In the process of changing the wavelength of the injected light, when the injected light (indicated by an arrow) approaches to the middle of the two modes (as shown in fig. 3 (a, b and f)), the generated optical frequency comb has a larger bandwidth; and when the injected light is located near the mode peak (as in fig. 3 (c, d, e)), the bandwidth of the resulting optical frequency comb is smaller. In addition, the introduction of light injection can greatly improve the carrier-to-noise ratio of each comb line in the bandwidth range.

Fig. 4 is a spectrum of an optical frequency comb produced by double light injection under optimized conditions. Wherein, the power and wavelength of the two injected lights are respectively: (P _inj1， λ _inj1 ）= （4.298 µW，1542.4605 nm），（P _inj2 ,λ _inj2 ) = (3.400 μw, 1543.0185 nm). The arrows indicate the locations where the two injected light wavelengths are located. As can be seen in fig. 4, the bandwidth of the entire optical frequency comb reaches 145.6 GHz (92 comb lines), approximately twice that of a single optical injection. Careful examination of the light injection locations (arrows) will reveal that both light injections are in the middle of the two modes, and that the two light injections are separated by two modes (about 0.28, nm). The method has the advantages that the operation is simple, the beneficial effect is obvious, and the optical frequency comb with the bandwidth reaching 145 GHz and the adjustable center wavelength can be obtained by selecting matched double-light injection parameters.

In conclusion, the above experiment fully verifies the excellent effects of the technical scheme of the invention, and the beneficial effects achieved by the invention are as follows: compared with a common optical frequency comb generator, the invention adopts a weak resonant cavity Fabry-Perot laser, and the laser has the characteristics of long cavity length, low reflectivity of the front end surface and the like, and can realize simultaneous lasing of multiple longitudinal modes and large mode output share; the driving current of the weak resonant cavity Fabry-Perot laser is directly modulated by adopting sinusoidal current, and the direct modulation structure has the advantages of simple system, low cost, easy realization, convenient tuning and the like, and can realize continuous adjustment of comb pitch by simply changing the frequency of an output signal of a microwave frequency synthesizer; the optical frequency comb with the tunable central wavelength range and the bandwidth periodically changing along with the wavelength of the injected light is produced through single light injection, then the bandwidth of the optical comb is expanded through double light injection, and the matched double light injection parameters are selected, so that the high-quality optical frequency comb with the adjustable central wavelength and the bandwidth exceeding 145 GHz can be obtained.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.

Claims (5)

1. A device for generating a broadband optical frequency comb with an adjustable center wavelength, characterized in that: the tunable laser comprises a weak resonant cavity Fabry-Perot laser 600, a direct modulation module 700, a tunable laser source 100, a tunable laser source 200, a light injection module 300, a light circulator 400 and an optical frequency comb detection module 500;

the weak resonant cavity fabry-perot laser 600 is a multi-longitudinal mode laser, which can simultaneously laser a plurality of longitudinal modes during free running, and is used for generating optical frequency comb signals with a large-range tuning center wavelength;

the direct modulation module 700 is configured to output a high-power sinusoidal current signal with a frequency of 1.6GHz and a power of 19 dBm, and after the sinusoidal signal and the dc bias are superimposed by a T-shaped bias, perform current modulation on the weak resonant cavity fabry-perot laser 600, and drive the weak resonant cavity fabry-perot laser 600 to present a gain switching state, where the direct modulation module 700 is connected with the weak resonant cavity fabry-perot laser 600;

the tunable laser sources 100 and 200 are used for providing continuous optical signals;

the optical injection module 300 is used for injecting continuous optical signals output by the tunable laser sources 100 and 200 into the optical circulator 400, and the optical injection module 300 is connected with the tunable laser sources 100 and 200 and the optical circulator 400;

the optical circulator 400 is configured to inject a continuous optical signal into the weak resonator fabry-perot laser 600, and send an optical frequency comb signal output by the weak resonator fabry-perot laser 600 to the optical frequency comb detection module 500, where the optical circulator 400 is connected to the optical injection module 300, the optical frequency comb detection module 500, and the weak resonator fabry-perot laser 600, respectively;

the optical frequency comb detection module 500 is used for detecting the optical frequency comb performance output by the weak cavity fabry-perot laser 600, and the optical frequency comb detection module 500 is connected with the optical circulator 400.

2. The device for generating a broadband optical frequency comb with an adjustable center wavelength according to claim 1, wherein: the direct modulation module 700 includes a microwave frequency synthesizer 701, a dc power supply 702, and a T-bias 703;

the microwave frequency synthesizer 701 is configured to output sinusoidal current with adjustable frequency fm and adjustable power Pm;

the dc power supply 702 is used to provide dc bias current required by the laser;

the T-type bias 703 is configured to couple the sinusoidal current and the dc bias current into one path, and then load the sinusoidal current and the dc bias current onto the working current of the weak cavity fp ld 600, so that the weak cavity fp ld 600 presents a gain switching state.

3. The device for generating a broadband optical frequency comb with an adjustable center wavelength according to claim 1, wherein: the light injection module 300 comprises a first light attenuator 301, a first polarization controller 302, a first light coupler 303, a second light attenuator 304, a second polarization controller 305, a second light coupler 306, a third light coupler 308, a first light power meter 307, and a second light power meter 309;

the first optical attenuator 301 is used for adjusting the magnitude of continuous optical power output by the tunable laser source 100, wherein the first optical attenuator 301 is connected with the tunable laser source 100 and the first polarization controller 302;

the second optical attenuator 304 is used for adjusting the magnitude of the continuous optical power output by the tunable laser source 200, wherein the second optical attenuator 304 is connected with the tunable laser source 200 and the second polarization controller 305;

the first polarization controller 302 is configured to adjust a polarization state of an optical signal output by the tunable laser source 100, where the first polarization controller 302 is connected to the first optical attenuator 301 and the first optical coupler 303;

the second polarization controller 305 is configured to adjust a polarization state of the optical signal output by the tunable laser source 200, where the second polarization controller 305 is connected to the second optical attenuator 304 and the second optical coupler 306;

the first optical coupler 303 is configured to divide the continuous light output by the tunable laser source 100 into two parts during single light injection, wherein a part of the continuous light enters the first optical power meter 307, and is used to measure the optical power of the first injected light, and another part of the continuous light is unidirectionally injected into the weak cavity fabry-perot laser 600 after passing through the third optical coupler 308 and the optical circulator 400, so as to drive the weak cavity fabry-perot laser 600 in a gain switching state to generate an optical frequency comb with an adjustable center wavelength, where the first optical coupler 303 is respectively connected to the first polarization controller 302, the first optical power meter 307 and the third optical coupler 308;

the second optical coupler 306 is configured to divide the continuous light output by the tunable laser source 200 into two parts during the dual-light injection, wherein a part of the continuous light enters the second optical power meter 309 for measuring the optical power of the second injected light, and another part of the continuous light is coupled with a part of the continuous light output by the tunable laser source 100 at the third optical coupler 308, where the second optical coupler 306 is connected to the second polarization controller 305, the second optical power meter 309 and the third optical coupler 308, respectively;

the third optical coupler 308 is configured to couple a part of light output by each of the tunable laser source 100 and the tunable laser source 200 into a whole at the third optical coupler 308 during the dual-optical injection, and then inject the light into the weak cavity fp ld 600 in a unidirectional manner after passing through the optical circulator 400, so as to drive the weak cavity fp ld 600 to generate an optimized optical frequency comb.

4. The device for generating a broadband optical frequency comb with an adjustable center wavelength according to claim 1, wherein: the optical frequency comb detection module 500 comprises a fourth optical coupler 501, a spectrum analyzer 502, a fifth optical coupler 503, a first photoelectric detector 504, a second photoelectric detector 505, a spectrum analyzer 506 and a digital oscilloscope 507 which are sequentially connected;

the optical signal output from the optical circulator 400 enters the fourth optical coupler 501 to be split, one part of the split optical signal enters the spectrum analyzer 502 to be subjected to spectrum measurement, the other part of the split optical signal enters the fifth optical coupler 503 to be split again, one part of the split optical signal is converted into an electric signal by the first photoelectric detector 504 through the fifth optical coupler 503 and then is input into the spectrum analyzer 506 to observe a frequency spectrum, and the other part of the split optical signal is converted into an electric signal by the second photoelectric detector 505 and then is input into the digital oscilloscope 507 to be subjected to time series measurement.

5. A method for generating a broadband optical frequency comb with an adjustable center wavelength, using a generating device for a broadband optical frequency comb with an adjustable center wavelength according to any one of claims 1 to 4, comprising the steps of:

step one: the microwave frequency synthesizer 701 outputs a sinusoidal modulation signal with the frequency of 1.6GHz and the power of 19 dBm, and the sinusoidal modulation signal and the direct current output by the direct current power supply 702 are superimposed through the T-shaped bias device 703 and then are loaded onto the working current of the weak resonant cavity Fabry-Perot laser 600 together, so that the weak resonant cavity Fabry-Perot laser 600 presents a gain switching state;

step two: the tunable laser source 100 outputs a continuous optical signal with adjustable wavelength and power, the continuous optical signal is divided into two parts after passing through the first optical attenuator 301, the first polarization controller 302 and the first optical coupler 303, and one part (such as 10%) enters the first optical power meter 307 to monitor the injection power;

step three: another part (for example, 90%) of the output from the first optical coupler 303 is injected into the weak cavity fabry-perot laser 600 in a unidirectional manner after passing through the third optical coupler 308 and the optical circulator 400, so that the weak cavity fabry-perot laser 600 in a gain switching state is driven to generate an optical frequency comb with a center wavelength which is adjustable in a large range and a bandwidth which is periodically changed between 30.4 GHz and 76.8 GHz along with the increase of the wavelength of the injected light;

step four: in order to further improve the optical frequency comb performance generated by the single light injection corresponding to the first to third steps, the second tunable laser source 200 is additionally introduced, and the dual light injection is adopted to the weak resonant cavity fabry-perot laser 600 in the gain switch state, so that the optical frequency comb signal with larger bandwidth and adjustable central wavelength in a large range can be obtained compared with the single light injection. During dual light injection, the continuous light signal output by the second tunable laser source 200 is divided into two parts after passing through the second optical attenuator 304, the second polarization controller 305 and the second optical coupler 306, wherein one part (such as 10%) enters the second optical power meter 309 to monitor the magnitude of the second beam injection light power;

step five: another portion (e.g., 90%) of the light output from the second optical coupler 306 and a portion (e.g., 90%) of the light output from the first optical coupler 303 are coupled into one path by the third optical coupler 308, and then are double-optically injected into the fabry-perot laser 600 with a weak resonant cavity by the optical circulator 400, and when the two injected lights are located between the two modes of the laser 600 and the wavelength difference between the two injected lights is about twice the mode spacing (about 0.28 nm) of the laser 600, a high-quality optical frequency comb with a bandwidth exceeding 145 GHz and an adjustable center wavelength can be obtained, and the high-quality frequency comb signal can be observed from the detection module 500.