A frequency-swept pulsed laser

Abstract

The embodiment of the present application provides a kind of frequency scanning pulse laser and method, multiple different wavelength laser is emitted by multiple wavelength continuous laser emitter and is transmitted to semiconductor optical amplifier, semiconductor optical amplifier is modulated as multiple different wavelength and time synchronization laser pulse, is transmitted to optical fiber circulator, optical fiber circulator is transmitted to optical pulse timing control module, optical pulse timing control module is received multiple different wavelength and time synchronization laser pulse in turn reflected to optical fiber circulator, and multiple wavelength laser pulse is separated in space in time synchronization, to output in time sequence in turn arranged laser pulse, relative to EOM or other optical modulator, it is lower in cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of laser, in particular to a frequency scanning pulse laser. BACKGROUND

[0002] The swept laser source / wavelength scanning laser source, namely the frequency scanning pulse laser, is a linearly tunable laser source with time encoding, and the output wavelength is linearly scanned and output at a certain time interval. The main parameters include swept speed, swept range, instantaneous linewidth, etc. The swept laser source is mainly applied to optical coherence tomography (OCT), optical frequency domain reflectometer (OFDR), optical fiber communication and optical sensing demodulation, etc.

[0003] A good frequency scanning pulse laser should have the characteristics of fast scanning speed, large swept range, narrow instantaneous linewidth, good linearity and high output power, and the output laser wavelength can be linearly output at a certain step (i.e. wavelength interval of laser tuning). It mainly consists of three parts, namely a light amplifier with a wide gain spectrum range, a time-controllable bandpass filter and a corresponding coupling output device.

[0004] The time sequence of light of different wavelengths needs to be controlled in the above light source. At present, it is realized by an electro-optic modulator (EOM) that a plurality of electro-optic modulators are sequentially selected according to a preset time interval within a preset time length, so as to form a wavelength sequence with a fixed time interval in the time domain; but if 20 lasers of different wavelengths are used to form the structure, 20 EOMs or other optical modulators are needed to realize the frequency scanning pulse laser, which is very high in cost. SUMMARY

[0005] The embodiment of the present application provides a frequency scanning pulse laser. A plurality of laser pulses of different wavelengths and time synchronization are transmitted at different lengths, so that they can be sequentially arranged in time sequence when output, and a wavelength sequence with a fixed time interval in the time domain is formed, without using an EOM or other optical modulator, and the cost is lower.

[0006] The embodiment of the present application provides a frequency scanning pulse laser, which comprises a multi-wavelength continuous laser emitter, a semiconductor optical amplifier, a signal generator, a fiber ring and an optical pulse time sequence control module.

[0007] The multi-wavelength continuous laser emitter, the semiconductor optical amplifier, the optical fiber circulator and the optical pulse timing control module are connected in sequence through a first optical fiber;

[0008] The semiconductor optical amplifier and the signal generator are electrically connected;

[0009] The multi-wavelength continuous laser emitter is used for emitting continuous lasers of multiple different wavelengths;

[0010] The semiconductor optical amplifier receives the continuous lasers emitted by the multi-wavelength continuous laser emitter and emits laser pulses of a certain pulse duration after modulating the continuous lasers;

[0011] The signal generator is used for emitting a square wave signal and modulating the semiconductor optical amplifier through the square wave signal;

[0012] The first port of the optical fiber circulator is used for receiving the multiple different wavelengths and time-synchronized laser pulses emitted by the semiconductor optical amplifier and transmitting to the second port of the optical fiber circulator, the second port of the optical fiber circulator is used for transmitting the multiple different wavelengths and time-synchronized laser pulses to the optical pulse timing control module, and the third port of the optical fiber circulator is used for sequentially outputting the laser pulses of different wavelengths along a certain timing;

[0013] The optical pulse timing control module has a reflection assembly, which is used for sequentially reflecting the received multiple different wavelengths and time-synchronized laser pulses to the optical fiber circulator, so as to sequentially output the laser pulses of different wavelengths at the third port of the optical fiber circulator.

[0014] In a feasible implementation, the reflection assembly includes multiple fiber gratings, the multiple fiber gratings are connected in a string through a second optical fiber in sequence, one of the fiber gratings at the end of the string is connected to the second port of the optical fiber circulator through the first optical fiber;

[0015] The wavelength of the fiber grating corresponds to the wavelength of the laser pulse one by one, and the fiber grating is used for reflecting the laser pulse of the corresponding wavelength back to the second port of the optical fiber circulator.

[0016] In a feasible implementation, the length of the second optical fiber is L, where L≥cτ / 2n;

[0017] In the formula, c is the propagation speed of the laser pulse in vacuum, τ is the duration of the laser pulse, and n is the refractive index of the second optical fiber.

[0018] In an implementation, the reflection component includes a dense wavelength division multiplexer and a plurality of fiber Faraday rotator mirrors;

[0019] The dense wavelength division multiplexer is connected to the second port of the fiber circulator through a first optical fiber;

[0020] The wavelengths of the optical paths in the dense wavelength division multiplexer correspond to and are equal to the wavelengths of the plurality of laser pulses;

[0021] The plurality of fiber Faraday rotator mirrors correspond to the optical paths one by one, and each fiber Faraday rotator mirror is connected to the corresponding optical path in the dense wavelength division multiplexer through a second optical fiber. The lengths of the second optical fibers corresponding to the plurality of fiber Faraday rotator mirrors are different;

[0022] The dense wavelength division multiplexer is configured to receive the plurality of laser pulses of different wavelengths and time synchronization, transmit the laser pulses of corresponding wavelengths to the corresponding fiber Faraday rotator mirrors through the corresponding optical paths and the second optical fibers of corresponding lengths, and reflect the laser pulses of corresponding wavelengths to the second port of the fiber circulator through the fiber Faraday rotator mirrors and the dense wavelength division multiplexer.

[0023] In an implementation, the lengths of the second optical fibers form an arithmetic sequence, so that the laser pulses of different wavelengths are reflected to the second port of the fiber circulator at the same time interval.

[0024] In an implementation, the common difference d of the arithmetic sequence is greater than or equal to cτ / 2n.

[0025] In the formula, c is the propagation speed of the laser pulses in vacuum, τ is the duration of the laser pulses, and n is the refractive index of the second optical fiber.

[0026] In an implementation, the multi-wavelength continuous laser emitter includes a plurality of continuous laser emitters of different wavelengths and a dense wavelength division multiplexer. The plurality of continuous laser emitters are respectively connected to the dense wavelength division multiplexer through first optical fibers;

[0027] The dense wavelength division multiplexer is connected to the first port of the fiber circulator through a first optical fiber;

[0028] The wavelengths of the plurality of continuous laser emitters correspond to and are equal to the wavelengths of the dense wavelength division multiplexer respectively.

[0029] In an implementation, the multi-wavelength continuous laser emitter includes an active fiber grating string, a first pump source, a second pump source, a first wavelength division multiplexer, a second wavelength division multiplexer, an isolator, and an optical amplifier.

[0030] The optical amplifier is connected to the first port of the fiber circulator through a first optical fiber;

[0031] The active fiber grating string is connected by a plurality of active pi phase shift fiber gratings of different wavelengths in sequence;

[0032] The first and second wavelength division multiplexers are respectively located on both sides of the active fiber grating string along the light path and are connected to the active fiber grating string through a first optical fiber;

[0033] The first wavelength division multiplexer is connected to the first pump source and the isolator through a first optical fiber, and the isolator is connected to the optical amplifier through a first optical fiber;

[0034] The second wavelength division multiplexer is connected to the second pump source through a first optical fiber.

[0035] In a feasible implementation, the multi-wavelength continuous laser emitter includes a broadband light source, a fiber Fabry-Perot etalon, and an optical amplifier, which are connected in sequence through a first optical fiber, and the optical amplifier is connected to the first port of the fiber circulator through a first optical fiber.

[0036] In a feasible implementation, the wavelength interval of the transmission peak of the fiber Fabry-Perot etalon is equal to its free spectral range;

[0037] The wavelength width of the transmission peak of the fiber Fabry-Perot etalon is the ratio of its free spectral range and fineness.

[0038] The frequency scanning pulse laser provided by the embodiment of the present application emits a plurality of continuous lasers of different wavelengths through the multi-wavelength continuous laser emitter and transmits them to the semiconductor optical amplifier. The semiconductor optical amplifier and the signal generator modulate them into a plurality of laser pulses of different wavelengths and time synchronization, and then transmit them to the fiber circulator. The fiber circulator transmits the laser pulses to the optical pulse timing control module. The time-synchronized multi-wavelength laser pulses are reflected back to the fiber circulator through the reflection assembly in sequence, and the time-synchronized multi-wavelength laser pulses are separated in space, so as to output the laser pulses which are sequentially arranged in time sequence. Compared with the EOM or other optical modulators, the cost is lower. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a structural schematic diagram of the frequency scanning pulse laser provided by an embodiment of the present application;

[0040] Figure 2 is an output schematic diagram of the laser pulse modulated by the semiconductor optical amplifier provided by an embodiment of the present application;

[0041] Figure 3 is a schematic diagram of the output laser pulse of the fiber circulator provided by an embodiment of the present application;

[0042] Figure 4 is a schematic diagram of a structure of the reflection assembly provided by an embodiment of the present application;

[0043] Figure 5 is another schematic diagram of a structure of the reflection assembly provided by an embodiment of the present application;

[0044] Figure 6 is a schematic diagram of a first embodiment of the multi-wavelength continuous laser emitter;

[0045] Figure 7 is a schematic diagram of a second embodiment of the multi-wavelength continuous laser emitter;

[0046] Figure 8 is a schematic diagram of a third embodiment of the multi-wavelength continuous laser emitter;

[0047] Figure 9 is a schematic diagram of an alternative embodiment of the semiconductor optical amplifier and the signal generator.

[0048] BRIEF DESCRIPTION OF DRAWINGS

[0049] 1 - multi-wavelength continuous laser emitter; 2 - fiber isolator; 3 - semiconductor optical amplifier; 4 - signal generator; 5 - fiber circulator; 6 - optical pulse timing control module; 7 - first optical fiber;

[0050] 81 - first fiber grating; 82 - second fiber grating; 83 - third fiber grating; 8N-1 - N-1th fiber grating; 8N - Nth fiber grating;

[0051] 9 - dense wavelength division multiplexer; 101 - first fiber Faraday rotator mirror; 102 - second fiber Faraday rotator mirror; 1N-1 - N-1th fiber Faraday rotator mirror; 1N - Nth fiber Faraday rotator mirror;

[0052] 101a - first continuous laser emitter; 102a - second continuous laser emitter; 103a - third continuous laser emitter; 1Na - Nth continuous laser emitter;

[0053] 101b - active fiber grating string; 102b - first pump source; 103b - second pump source; 104b - first wavelength division multiplexer; 105b - second wavelength division multiplexer; 106b - isolator; 107b - first optical amplifier;

[0054] 101c - broadband light source; 102c - fiber Fabry-Perot etalon;

[0055] 201 - second optical amplifier; 202 - optical modulator; 300 - second optical fiber. DETAILED DESCRIPTION

[0056] In order for those skilled in the art to better understand the technical solutions in the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0057] In the currently applied technology, the lasers output by each wavelength output channel are transmitted to an electro-optical modulator respectively, and a controller outputs a control signal to control the work of the electro-optical modulator, so as to realize the output of a certain wavelength, so as to realize the selection of one of the multiple electro-optical modulators in a preset time interval in a preset time length, so as to form a wavelength sequence with a fixed time interval in the time domain. In this way, the multiple wavelengths of laser are completed by the time domain control method based on the electro-optical modulator, and the pulse light formed by the continuous splicing of multiple pulse lights is obtained.

[0058] However, if 20 lasers are output by 20 output channels with different wavelengths, 20 electro-optical modulators or other optical modulators are needed to realize the pulse light modulation, and a controller also needs to be configured, so the cost is very high.

[0059] Based on the above problems, the embodiment of the present application provides a frequency scanning pulse laser, which changes the transmission paths of multiple wavelengths of laser, and distinguishes the multiple wavelengths of laser in space through the differences in the transmission paths, so as to form a wavelength sequence with a fixed time interval in the time domain when output.

[0060] Figure 1 is a structural schematic diagram of the frequency scanning pulse laser provided by an embodiment of the present application. As shown in Figure 1 The embodiment of the present application provides a frequency scanning pulse laser, which comprises a multi-wavelength continuous laser emitter 1, an optical fiber circulator 5 and an optical pulse time sequence control module 6, and the multi-wavelength continuous laser emitter 1, the optical fiber circulator 5 and the optical pulse time sequence control module 6 are connected in sequence through a first optical fiber 7.

[0061] In some examples, the multi-wavelength continuous laser emitter 1 and the optical fiber circulator 5 can be connected through an optical fiber isolator 2 and a semiconductor optical amplifier 3, for example, the multi-wavelength continuous laser emitter 1, the optical fiber isolator 2, the semiconductor optical amplifier 3 and the optical fiber circulator 5 can be connected in sequence through the first optical fiber 7. In addition, the semiconductor optical amplifier 3 can also be electrically connected with a signal generator 4 through a wire.

[0062] The multi-wavelength continuous laser emitter 1 is used to emit continuous laser beams of multiple different wavelengths.

[0063] The optical fiber isolator 2 is used to prevent backward scattering and reflected light from entering the multi-wavelength continuous laser 1, so as to avoid affecting the parameters of the multi-wavelength continuous laser emitter 1.

[0064] Figure 2 is a schematic diagram of the output of the modulated laser pulse of the semiconductor optical amplifier. Referring to Figure 2 As shown in the figure, the semiconductor optical amplifier 3 receives the continuous laser beams emitted by the multi-wavelength continuous laser emitter 1 and emits laser pulses of a certain pulse duration after modulating the continuous laser beams.

[0065] The signal generator 4 is used to emit a square wave signal and modulate the semiconductor optical amplifier 3 through the square wave signal.

[0066] Referring to Figure 1 As shown in the figure, when specifically connected, the multi-wavelength continuous laser emitter 1 can be connected with the first port 51 of the optical fiber circulator 5 through the first optical fiber 7, the optical fiber isolator 2 and the semiconductor optical amplifier 3, and the first port 51 of the optical fiber circulator 5 is used to receive multiple different wavelengths and time-synchronized laser pulses and send them to the second port 52 of the optical fiber circulator 5.

[0067] In addition, the second port 52 of the optical fiber circulator 5 can be connected with the optical pulse timing control module 6 through the first optical fiber 7, and the second port 52 of the optical fiber circulator 5 is used to send multiple different wavelengths and time-synchronized laser pulses to the optical pulse timing control module 6 and sequentially receive multiple different wavelengths of laser pulses reflected back by the optical pulse timing control module 6, and the third port 53 of the optical fiber circulator 5 is used to sequentially output laser pulses of different wavelengths along a certain timing.

[0068] Figure 3 is a schematic diagram of the output of the laser pulse of the optical fiber circulator. Referring to Figure 3 As shown in the figure, the optical pulse timing control module 6 has a reflection component, which is used to sequentially reflect the received multiple different wavelengths and time-synchronized laser pulses into the optical fiber circulator 5, so as to sequentially output laser pulses of different wavelengths from the third port 53 of the optical fiber circulator 5.

[0069] It can be understood that the specific structure and working principle of the optical fiber circulator 5 can refer to the related contents of the optical fiber circulator 5 in the prior art, which will not be described here.

[0070] The frequency scanning pulse laser provided by the embodiment of the present application is characterized in that: the multi-wavelength continuous laser emitter 1 emits laser beams of different wavelengths and transmits the laser beams to the semiconductor optical amplifier 3; the semiconductor optical amplifier 3 and the signal generator 4 modulate the laser beams into laser pulses of different wavelengths and time synchronization, and then transmit the laser pulses to the optical fiber circulator 5; the optical fiber circulator 5 transmits the laser pulses to the optical pulse timing control module 6; the laser pulses are reflected back to the optical fiber circulator 5 by the reflection assembly in sequence, and the time-synchronized multi-wavelength laser pulses are separated in space, so that the laser pulses are output in time sequence. Compared with the EOM or other optical modulators, the cost is lower.

[0071] Figure 4 is another structural schematic diagram of the reflection assembly provided by the embodiment of the present application. As shown in Figure 4 , the reflection assembly in the embodiment of the present application can include a plurality of fiber gratings, Figure 4 , in which, the number 81 represents the first fiber grating (FBG1), the number 82 represents the second fiber grating (FBG2), the number 83 represents the third fiber grating (FBG3), the number 8N-1 represents the (N-1)th fiber grating (FBG N-1 ), and the number 8N represents the Nth fiber grating (FBG N ). Figure 4 As shown in , in some examples, the reflection assembly includes N fiber gratings, i.e., the first fiber grating 81, the second fiber grating 82, the third fiber grating 83, …, the (N-1)th fiber grating 8N-1, and the Nth fiber grating 8N.

[0072] The N fiber gratings are connected in a string by the equal-length second optical fiber 300, and one of the fiber gratings at the end of the string is connected to the second port 52 of the optical fiber circulator 5 through the first optical fiber 7.

[0073] For example, the first fiber grating 81 (FBG1) is connected to the second port 52 of the optical fiber circulator 5 through the first optical fiber 7.

[0074] The wavelength of the fiber grating corresponds to the wavelength of the laser pulse one by one, and the fiber grating is used to reflect the laser pulse of the corresponding wavelength back to the second port 52 of the optical fiber circulator 5.

[0075] Furthermore, the center wavelengths of the reflection spectra of the N fiber gratings are respectively the center wavelengths λ1, λ2, … λ N of the multi-wavelength continuous laser emitter 1, the matching effect is better when the center wavelengths are consistent, and it is more conducive to the fiber grating to reflect the laser pulse of the corresponding wavelength back.

[0076] The laser pulses output from the semiconductor optical amplifier 3 enter the optical pulse timing control module 6 through the first port 51 of the fiber optic circulator 5 and the second port 52 of the fiber optic circulator 5, with center wavelengths of λ1, λ2, ... λ. N The laser pulses sequentially pass through FBG1, FBG2, ..., FBG in the optical pulse timing control module 6. N The laser pulse with a center wavelength of λ1 is reflected back to the second port 52 of the fiber optic circulator 5 by the fiber optic grating of the corresponding wavelength. For example, a laser pulse with a center wavelength of λ1 is reflected back to the second port 52 by the FBG1. At this time, λ1, λ2, ..., λ N The laser pulses are separated according to time sequence. The duration of each wavelength laser pulse is τ, and the total duration is ΔT = Nτ. Finally, the laser pulses with wavelength scanning over time are output through the third port 53 of the fiber optic circulator 5.

[0077] It should be noted that the peak reflectance of the reflection spectrum of these N fiber gratings should be as high as possible, usually greater than 99%, but not limited to this.

[0078] In addition to solving the problem of high cost of electro-optic modulation, the embodiments of this application can also filter the spontaneous emission light introduced by the semiconductor optical amplifier 3, thereby improving the signal-to-noise ratio of frequency scanning pulse laser.

[0079] In the above embodiment, the length L of the second optical fiber 300 is determined by the duration τ of the laser pulse, for example, L≥cτ / 2n. Where: c is the propagation speed of the laser pulse in a vacuum, and n is the refractive index of the second optical fiber 300.

[0080] For example, if the propagation speed of the laser pulse in a vacuum is c = 300000000m / s, the refractive index n of the second optical fiber 300 is 1.45, and the duration τ of the laser pulse is 10ns, then the length L of the second optical fiber 300 should be greater than or equal to 1.034m.

[0081] The embodiments of this application can avoid the reflection interval of two adjacent wavelength laser pulses being too short, thereby avoiding the situation where two adjacent wavelength laser pulses overlap in the time domain.

[0082] It should be noted that, in order to ensure the continuity of the frequency-sweeping laser output in the time domain, L = cτ / 2n can be taken.

[0083] Figure 5 This is a schematic diagram of another structure of the reflective component provided in one embodiment of this application. Figure 5 In the diagram, number 9 indicates a dense wavelength division multiplexer (DWDM), as shown in the reference. Figure 5As shown, in another embodiment, the reflection assembly comprises a dense wavelength division multiplexer 9 and a plurality of fiber Faraday rotator mirrors (F-FRM) ;

[0084] The dense wavelength division multiplexer 9 is connected to the second port 52 of the fiber loop 5 through the first optical fiber 7.

[0085] The wavelengths of the optical paths in the dense wavelength division multiplexer 9 correspond to and are equal to the wavelengths of the plurality of laser pulses.

[0086] Similarly to the foregoing embodiment, the center wavelengths of the two are correspondingly matched.

[0087] The plurality of fiber Faraday rotator mirrors are arranged in one-to-one correspondence with the optical paths, and each fiber Faraday rotator mirror is connected to the corresponding optical path in the dense wavelength division multiplexer 9 through a second optical fiber 300, and the lengths of the second optical fibers 300 corresponding to the plurality of fiber Faraday rotator mirrors are different.

[0088] The fiber Faraday rotator mirrors comprise a first fiber Faraday rotator mirror 101, a second fiber Faraday rotator mirror 102, …, an (N-1)th fiber Faraday rotator mirror 1N-1, and an Nth fiber Faraday rotator mirror 1N. The length of the second optical fiber 300 corresponding to the first fiber Faraday rotator mirror 101 is L0, L0 represents an arbitrary length of the second optical fiber 300, and 1 m or 2 m is usually selected. The length of the second optical fiber 300 corresponding to the second fiber Faraday rotator mirror 102 is L0+L, L represents a certain length of the second optical fiber 300, and so on. The length of the second optical fiber 300 corresponding to the (N-1)th fiber Faraday rotator mirror is L0+(N-2)L, and the length of the second optical fiber 300 corresponding to the Nth fiber Faraday rotator mirror 1N is L0+(N-1)L.

[0089] The dense wavelength division multiplexer 9 is used to receive a plurality of laser pulses of different wavelengths and time synchronization, and transmit the laser pulses of corresponding wavelengths to the corresponding fiber Faraday rotator mirrors through the corresponding optical paths and the second optical fibers 300 of corresponding lengths, so as to reflect the laser pulses of corresponding wavelengths to the second port 52 of the fiber loop 5 through the fiber Faraday rotator mirrors and the dense wavelength division multiplexer.

[0090] The embodiments of the present application transmit a plurality of laser pulses of different wavelengths and time synchronization through different transmission paths, and the lengths of the transmission paths are different, so as to separate the laser pulses of different wavelengths from each other in the time domain, thereby solving the problem of high cost of electro-optical modulation.

[0091] In the above embodiment, the set of lengths of the second optical fiber 300 connecting the DWDM and the F-FRM forms an arithmetic sequence, so that the length difference of adjacent transmission paths is the same, so that the reflection interval of two laser pulses of adjacent transmission is the same, so that the laser pulses of different wavelengths are reflected to the second port 52 of the fiber circulator 5 with the same time interval.

[0092] In the above embodiment, the common difference d of the arithmetic sequence is greater than or equal to cτ / 2n.

[0093] In the formula, c is the propagation speed of the laser pulse in vacuum, τ is the duration of the laser pulse, and n is the refractive index of the second optical fiber 300.

[0094] As in the foregoing embodiment, the embodiment of the application can also avoid the reflection interval of two laser pulses of adjacent wavelengths being too short, thereby avoiding the case that two laser pulses of adjacent wavelengths overlap in time domain.

[0095] It should be noted that, in order to ensure the continuity of the swept laser output in time domain, i.e., the continuity of the laser pulses of multiple different wavelengths in time domain, d should be equal to cτ / 2n.

[0096] The following further describes several embodiments of the multi-wavelength continuous laser emitter 1.

[0097] Figure 6 The multi-wavelength continuous laser emitter 1 is a first embodiment, as shown in FIG. 1, which comprises a plurality of continuous laser emitters of different wavelengths and a dense wavelength division multiplexer 9. Figure 6 The plurality of continuous laser emitters of different wavelengths are a first continuous laser emitter 101a (wavelength λ1), a second continuous laser emitter 102a (wavelength λ2), a third continuous laser emitter 103a (wavelength λ3), …, and an Nth continuous laser emitter 1Na (wavelength λN), with a wavelength interval Δλ. N The plurality of continuous laser emitters are respectively connected to the dense wavelength division multiplexer 9 through a first optical fiber 7.

[0098] The dense wavelength division multiplexer 9 is connected to the first port 51 of the fiber circulator 5 through the first optical fiber 7.

[0099] The wavelengths of the plurality of continuous laser emitters respectively correspond to and are equal to the wavelengths of the dense wavelength division multiplexer 9.

[0100] It should be noted that, in order to make the instantaneous linewidth of the final swept laser narrow, the continuous laser emitters of N wavelengths usually emit narrow-linewidth, single-frequency laser with a linewidth of tens of MHz to hundreds of Hz.

[0101] Figure 7 is a second embodiment of the multi-wavelength continuous laser emitter 1, referring to Figure 7 As shown in the figure, the multi-wavelength continuous laser emitter 1 comprises an active fiber grating string 101b, a first pump source 102b, a second pump source 103b, a first wavelength division multiplexer 104b, a second wavelength division multiplexer 105b, an isolator 106b and a first optical amplifier 107b;

[0102] The first optical amplifier 107b is connected to the first port 51 of the fiber loop 5 through the first optical fiber 7;

[0103] The active fiber grating string 101b is connected by a plurality of active pi phase shift fiber gratings of different wavelengths in sequence;

[0104] The first wavelength division multiplexer 104b and the second wavelength division multiplexer 105b are respectively located on both sides of the active fiber grating string 101b along the light path, and are connected to the active fiber grating string 101b through the first optical fiber 7;

[0105] The first wavelength division multiplexer 104b is connected to the first pump source 102b and the isolator 106b through the first optical fiber 7, and the isolator 106b is connected to the first optical amplifier 107b through the first optical fiber 7;

[0106] The second wavelength division multiplexer 105b is connected to the second pump source 103b through the first optical fiber 7.

[0107] Exemplarily, taking the active pi phase shift fiber grating made of erbium-doped fiber and the pump source of 976 nm as an example, the first pump source 102b and the second pump source 103b are both semiconductor pump lasers of 976 nm, and the highest laser power is about 500 mW. They are connected to both ends of the active fiber grating string 101b through the first wavelength division multiplexer 104b of 976 nm and the second wavelength division multiplexer 105b of 1550 nm respectively, and the pump mode adopts a double-end pump mode, which can effectively improve the power and the power flatness of the N-wavelength laser. The formed laser is output through the first wavelength division multiplexer 104b, the first wavelength division multiplexer 104b is connected to the isolator 106b, so as to avoid the backscattered light from entering the laser device, thereby avoiding affecting the noise of the laser. The isolator 106b is connected to the first optical amplifier 107b, so as to further improve the output power of the N-wavelength laser, and finally obtain the multi-wavelength continuous laser with high output power.

[0108] In the embodiment of the application, since the active pi phase shift fiber grating is used as the laser emitting unit, the length of the device is only a few centimeters, so that the volume of the multi-wavelength continuous laser emitter 1 is smaller, and the linewidth of the emitted laser is less than 3 kHz, which has the characteristic of narrow linewidth.

[0109] Figure 8 This is the third embodiment of the multi-wavelength continuous laser emitter 1, see reference. Figure 8 As shown, the multi-wavelength continuous laser emitter 1 includes a broadband light source 101c, a fiber Fabry-Perot etalon 102c, and a first optical amplifier 107b. The broadband light source 101c, the fiber Fabry-Perot etalon 102c, and the first optical amplifier 107b are connected in sequence through a first optical fiber 7. The first optical amplifier 107b is connected to the first port 51 of the fiber optic circulator 5 through the first optical fiber 7.

[0110] The light output from the broadband light source 101c passes through the fiber Fabry-Perot etalon 102c, with a wavelength interval of Δλ, forming a multi-wavelength continuous laser output. To improve the output of the multi-wavelength continuous laser, optical power is amplified by a first optical amplifier 107b, or by an optical fiber amplifier, semiconductor optical amplifier, etc.

[0111] It should be noted that the free spectral range of the fiber Fabry-Perot etalon 102c is typically 50 GHz, 100 GHz, or 200 GHz.

[0112] In the third embodiment described above, the wavelength spacing of the transmission peaks of the fiber Fabry-Paro etalon 102c is equal to its free spectral range.

[0113] The wavelength width of the transmission peak of the fiber Fabry-Perot etalon 102c is the ratio of its free spectral range to its fineness, enabling the formation of narrow-linewidth, multi-wavelength continuous laser output.

[0114] Figure 9 This is a schematic diagram of an alternative embodiment of a semiconductor optical amplifier and signal generator, with reference to... Figure 9 As shown, the two ends of the second optical amplifier 201 are connected to the optical fiber isolator 2 and the optical modulator 202 respectively through the first optical fiber 7. The optical modulator 202 is connected to the first port 51 of the optical fiber circulator 5 through the first optical fiber 7. The signal generator 4 is electrically connected to the optical modulator 202 through a wire.

[0115] The main function of the semiconductor optical amplifier 3 and the signal generator 4 is to modulate light into a laser pulse with a repetition frequency of f and a pulse duration of τ. Its main feature is that the semiconductor optical amplifier 3 can directly modulate the laser by driving it with an electrical pulse, and the response time is less than 1ns. As long as the rise time of the electrical pulse of the signal generator 4 is small enough, it can generate a laser pulse in the ns range. Therefore, the response speed is fast and the duration of the obtained optical pulse signal is short.

[0116] In the alternative embodiment, the second optical amplifier 201 can be a fiber amplifier or a semiconductor optical amplifier, and the optical modulator can be an acousto-optic modulator or an electro-optic modulator. The rise time of the acousto-optic modulator is about 30 ns, which is longer than the rise time of the optical modulation in the foregoing embodiment, and the difference is relatively large. The acousto-optic modulator can be applied to some optical systems that do not have high requirements on pulse time.

[0117] The embodiment of the present application provides a frequency scanning pulse laser. The multiple laser pulses of different wavelengths are transmitted and reflected through different lengths of paths by cooperation of the reflection assembly and the second optical fiber 300. The time sequence between the laser pulses is controlled by controlling the length of the second optical fiber 300, so that the wavelength is controllable in time sequence. The pulse light is output in linear scanning output at a certain time interval. The structure is simple, and the cost is lower.

[0118] It is easy to understand that, on the basis of the several embodiments provided by the present application, the embodiments of the present application can be combined, split, recombined and the like to obtain other embodiments, and these embodiments do not exceed the protection scope of the present application.

[0119] The above detailed description of the embodiments of the present application further describes the purposes, technical solutions and beneficial effects of the embodiments of the present application. It should be understood that the above is only a specific implementation of the embodiments of the present application, and is not used to limit the protection scope of the embodiments of the present application. Any modification, equivalent replacement, improvement and the like made on the basis of the technical solutions of the embodiments of the present application should be included in the protection scope of the embodiments of the present application.

Claims

1. A frequency swept pulsed laser, characterized in that, The application relates to a multi-wavelength continuous laser emitter (1), a semiconductor optical amplifier (3), a signal generator (4), a fiber ring (5) and a light pulse timing control module (6). The multi-wavelength continuous laser emitter (1), the semiconductor optical amplifier (3), the fiber ring (5) and the light pulse timing control module (6) are sequentially connected through first optical fibers; The semiconductor optical amplifier (3) and the signal generator (4) are electrically connected; The multi-wavelength continuous laser emitter (1) is used for emitting continuous lasers of multiple different wavelengths; The semiconductor optical amplifier (3) receives the continuous lasers emitted by the multi-wavelength continuous laser emitter (1) and emits laser pulses with a certain pulse duration after modulation; The signal generator (4) is used for emitting a square wave signal and modulating the semiconductor optical amplifier (3) through the square wave signal; The first port of the fiber ring (5) is used for receiving the multiple different wavelength and time-synchronized laser pulses emitted by the semiconductor optical amplifier (3) and transmitting to the second port of the fiber ring (5), the second port of the fiber ring (5) is used for transmitting the multiple different wavelength and time-synchronized laser pulses to the light pulse timing control module (6) and sequentially receiving the multiple different wavelength laser pulses reflected by the light pulse timing control module (6), and the third port of the fiber ring (5) is used for sequentially outputting the laser pulses of different wavelengths along a certain time sequence; The light pulse timing control module (6) has a reflection assembly, which is used for sequentially reflecting the received multiple different wavelength and time-synchronized laser pulses to the fiber ring (5) to sequentially output the laser pulses of different wavelengths at the third port of the fiber ring (5). The reflection assembly comprises multiple fiber gratings, the multiple fiber gratings are sequentially connected into a string through second optical fibers, one of the fiber gratings at the string end is connected to the second port of the fiber ring (5) through the first optical fiber; 2. The frequency swept pulsed laser of claim 1, wherein, The wavelength of the fiber grating corresponds to the wavelength of the laser pulse one by one, and the fiber grating is used for reflecting the laser pulse of the corresponding wavelength back to the second port of the fiber ring (5). The length of the second optical fiber is L, wherein L >= ctau / 2n; 3. The frequency swept pulsed laser of claim 2, wherein, In the formula, c is the propagation speed of the laser pulse in vacuum, tau is the duration of the laser pulse, and n is the refractive index of the second optical fiber. The reflection assembly comprises a dense wavelength division multiplexer and multiple fiber Faraday rotator mirrors; 4. The frequency swept pulsed laser of claim 1, wherein, The dense wavelength division multiplexer is connected to the second port of the fiber ring (5) through the first optical fiber; The wavelength of each optical path in the dense wavelength division multiplexer corresponds to and is equal to the wavelength of the multiple laser pulses one by one; The multiple fiber Faraday rotator mirrors correspond to the optical paths one by one, and each fiber Faraday rotator mirror is connected to the corresponding optical path in the dense wavelength division multiplexer through the second optical fiber, and the lengths of the second optical fibers corresponding to the multiple fiber Faraday rotator mirrors are different. ​ The dense wavelength division multiplexer is configured to receive the plurality of laser pulses of different wavelengths and time synchronization, and transmit the laser pulse of corresponding wavelength to the corresponding optical fiber Faraday rotating mirror through the corresponding optical path and the second optical fiber of corresponding length, so as to reflect the laser pulse of corresponding wavelength to the second port of the optical fiber circulator (5) through the optical fiber Faraday rotating mirror.

5. The frequency swept pulsed laser of claim 4, wherein, The length set of the second optical fiber forms an arithmetic sequence, so that the laser pulses of different wavelengths are reflected to the second port of the optical fiber circulator (5) at the same time interval.

6. The frequency swept pulsed laser of claim 5, wherein, The common difference d of the arithmetic sequence is greater than or equal to cτ / 2n. In the formula, c is the propagation speed of the laser pulse in vacuum, τ is the duration of the laser pulse, and n is the refractive index of the second optical fiber.

7. The frequency swept pulsed laser of any of claims 1-6, wherein, The multi-wavelength continuous laser emitter (1) comprises a plurality of continuous laser emitters of different wavelengths and a dense wavelength division multiplexer, and the plurality of continuous laser emitters are connected to the dense wavelength division multiplexer through first optical fiber connections respectively. The dense wavelength division multiplexer is connected to the first port of the optical fiber circulator (5) through a first optical fiber connection. The wavelengths of the plurality of continuous laser emitters correspond to and are equal to the wavelengths of the dense wavelength division multiplexer one by one.

8. The frequency swept pulsed laser of any of claims 1-6, wherein, The multi-wavelength continuous laser emitter (1) comprises an active fiber grating string, a first pump source, a second pump source, a first wavelength division multiplexer, a second wavelength division multiplexer, an isolator and an optical amplifier. The optical amplifier is connected to the first port of the optical fiber circulator (5) through a first optical fiber connection. The active fiber grating string is sequentially connected by a plurality of active pi phase shift fiber gratings of different wavelengths. The first wavelength division multiplexer and the second wavelength division multiplexer are respectively located on both sides of the active fiber grating string along the optical path, and are connected to the active fiber grating string through first optical fiber connections respectively. The first wavelength division multiplexer is connected to the first pump source and the isolator through first optical fiber connections respectively, and the isolator is connected to the optical amplifier through a first optical fiber connection. The second wavelength division multiplexer is connected to the second pump source through a first optical fiber connection.

9. The frequency swept pulsed laser of any of claims 1-6, wherein, The multi-wavelength continuous laser emitter (1) comprises a broadband light source, a fiber Fabry-Perot etalon and an optical amplifier, which are sequentially connected through first optical fiber connections, and the optical amplifier is connected to the first port of the optical fiber circulator (5) through a first optical fiber connection.

10. The frequency swept pulsed laser of claim 9, wherein, The wavelength interval of the transmission peak of the fiber Fabry-Perot etalon is equal to its free spectral range. The wavelength width of the transmission peak of the fiber Fabry-Perot etalon is the ratio of its free spectral range to its fineness.

Images