Intermediate infrared ultrashort pulse high-speed space laser communication system

Abstract

The invention discloses a mid-infrared ultrashort pulse high-speed space laser communication system, belongs to the technical field of space laser communication, and aims to solve the problem that the requirement of mid-infrared high-speed optical communication cannot be met due to the fact that only wavelength can be tuned and high repetition frequency output cannot be realized in the prior art. The system comprises a radio frequency signal generator, a 1062nm mode-locked laser, an arbitrary waveform signal generator, a 1553nm mode-locked laser, a first optical fiber delay line, a second optical fiber delay line, a first optical fiber collimator, a second optical fiber collimator, a first half-wave plate, a second half-wave plate, a first reflecting mirror, a first dichroscope, a first difference frequency crystal, an intermediate infrared optical filter, a second reflecting mirror, a third reflecting mirror, a second dichroscope and a 1062nm laser. The device comprises a first half-wave plate, a second half-wave plate, a third reflecting mirror, a second difference frequency crystal, a near-infrared optical filter, a third optical fiber collimator and an avalanche photodiode. According to the invention, high-repetition-frequency and high-conversion-efficiency mid-infrared pulse light output can be realized, long-distance and high-speed information transmission in the atmosphere is realized, and the device has a wide application prospect in the field of space laser communication.

Description

Technical Field

[0001] The invention relates to a mid-infrared ultrashort pulse high-speed space laser communication system, belonging to the technical field of space laser communication. Background Art

[0002] Since mid-infrared lasers are in the atmospheric window band and have stronger resistance to atmospheric turbulence than near-infrared bands, they have broad application prospects in the fields of atmospheric communications and infrared countermeasures.

[0003] At present, there are many methods to generate mid-infrared lasers, such as optical parametric oscillator (OPO), optical parametric amplifier (OPA), solid or fiber lasers doped with transition metal or rare earth ions, and difference frequency generation (DFG). Among them, the DFG method of generating mid-infrared lasers has a simple structure and high stability. In addition, in optical communication applications, information can be well copied to mid-infrared lasers.

[0004] In the DFG method of generating mid-infrared lasers, the difference frequency of two pulsed lasers has many advantages: pulsed light can release high peak power in a short time, which makes it more effective in some nonlinear optical processes; in optical communications, pulsed light can be multiplexed through different time windows to improve signal transmission efficiency. At present, most communications in the mid-infrared band use continuous light modulation, which results in the output mid-infrared beam power being very low and unable to meet the needs of long-distance high-speed information transmission in the atmosphere. Although reports on the generation of mid-infrared lasers by pulse light difference frequency have appeared, the repetition rate of the generated mid-infrared laser is too low to meet the needs of high-speed communication.

[0005] The Chinese patent publication number is "CN114156727A", which discloses "a mid-infrared ultra-short pulse laser light source", which obtains mid-infrared ultra-short pulses by combining OPO+DFG. However, the system can only tune the wavelength and cannot achieve high repetition rate output, thus failing to meet the needs of mid-infrared high-speed optical communication. Summary of the invention

[0006] In order to solve the problem that the prior art can only tune the wavelength but cannot achieve high repetition rate output and thus cannot meet the demand for mid-infrared high-speed optical communication, the present invention proposes a mid-infrared ultrashort pulse high-speed space laser communication system.

[0007] The present invention adopts the following technical solutions:

[0008] A mid-infrared ultrashort pulse high-speed space laser communication system, characterized in that the system comprises a radio frequency signal generator, a 1062nm mode-locked laser, an arbitrary waveform signal generator, a 1553nm mode-locked laser, a first optical fiber delay line, a second optical fiber delay line, a first optical fiber collimator, a second optical fiber collimator, a first half-wave plate, a second half-wave plate, a first reflector, a first dichroic mirror, a first difference frequency crystal, a mid-infrared filter, a second reflector, a third reflector, a second dichroic mirror, a 1062nm laser, a third half-wave plate, a fourth reflector, a second difference frequency crystal, a near-infrared filter, a third optical fiber collimator and an avalanche photodiode;

[0009] The radio frequency signal generator inputs a sine wave signal to the 1062nm mode-locked laser and the 1553nm mode-locked laser, and at the same time the radio frequency signal generator inputs a clock signal to the arbitrary waveform signal generator; the arbitrary waveform signal generator is connected to the 1553nm mode-locked laser through a radio frequency line, and sends a PRBS code to the 1553nm mode-locked laser;

[0010] The output ends of the 1062nm mode-locked laser and the 1553nm mode-locked laser are connected to the optical fiber delay line 1 and the optical fiber delay line 2 respectively through optical fibers, and the optical fiber delay line 1 and the optical fiber delay line 2 are connected to the optical fiber collimator 1 and the optical fiber collimator 2 respectively, and the pump light and the signal light respectively pass through the optical fiber delay line 1 and the optical fiber delay line 2, and then output parallel light through the optical fiber collimator 1 and the optical fiber collimator 2 respectively;

[0011] The pump light is incident on the half-wave plate 1 in parallel, and the signal light is incident on the half-wave plate 2 in parallel. The half-wave plate 1 and the half-wave plate 2 respectively control the polarization directions of the pump light and the signal light output. The pump light passes through the half-wave plate 1 and is incident on the reflector 1. After being reflected by the reflector 1, the pump light is incident on the dichroic mirror 1. After being reflected by the dichroic mirror 1, the signal light is incident on the difference frequency crystal 1. The signal light is transmitted through the dichroic mirror 1 and then merged with the pump light. The merged light generates mid-infrared band conversion light through the difference frequency crystal 1. The mid-infrared band conversion light passes through the mid-infrared filter to eliminate the residual pump light and signal light. Finally, the mid-infrared band conversion light is reflected by the reflector 2 and the reflector 3 in sequence.

[0012] The parallel light output by the 1062nm laser is incident on the half-wave plate three, and the polarization direction of the light is changed by the half-wave plate three. The light beam is incident on the reflector four after passing through the half-wave plate three, and then is incident on the dichroic mirror two after being reflected by the reflector four, and then is reflected by the dichroic mirror two. The reflected light is combined with the mid-infrared band conversion light reflected by the reflector three and then transmitted by the dichroic mirror two. The combined light is incident on the difference frequency crystal two to generate 1553nm near-infrared conversion light, and then the residual 1062nm light and the mid-infrared band conversion light are eliminated by the near-infrared filter; the near-infrared conversion light is incident on the optical fiber collimator three, and after passing through the optical fiber collimator three, it is coupled into the optical fiber and transmitted to the avalanche photodiode, and the avalanche photodiode performs photoelectric conversion and signal demodulation.

[0013] Beneficial effects of the present invention:

[0014] The 1062nm laser and 1553nm mode-locked laser of the present invention are both actively mode-locked pulse lasers to achieve high repetition rate pulse output, thereby achieving high-rate modulation and transmission of signals. Both the 1062nm laser and the 1553nm mode-locked laser can output mode-locked pulses to achieve high conversion efficiency output with mid-infrared lasers, thereby simultaneously increasing the transmission distance of mid-infrared lasers in the atmosphere and reducing power jitter.

[0015] The present invention controls the same repetition frequency output of pump light and signal light through a radio frequency signal generator, and controls the pulses of pump light and signal light to enter a difference frequency crystal at the same time through an optical fiber delay line, thereby outputting mid-infrared pulse laser.

[0016] The present invention can realize high repetition rate and high conversion efficiency mid-infrared pulse light output and can transmit information over long distances and at high speeds in the atmosphere. Therefore, it has broad application prospects in the field of space laser communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of a mid-infrared ultrashort pulse high-speed space laser communication system of the present invention.

[0018] Figure 2 A schematic diagram of the waveforms of the mode-locked pulse and signal provided by the present invention.

[0019] Figure 3 A waveform diagram of the mode-locked pulse modulation provided by the present invention.

[0020] Figure 4 This is a spectrum diagram of the mid-infrared converted light provided by the present invention.

[0021] Figure 5 The present invention provides an eye diagram of a demodulated signal at a receiving end. DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the accompanying drawings.

[0023] like Figure 1 As shown, a mid-infrared ultrashort pulse high-speed space laser communication system includes a radio frequency signal generator 1, a 1062nm mode-locked laser 2, an arbitrary waveform signal generator 3, a 1553nm mode-locked laser 4, an optical fiber delay line 1 5, an optical fiber delay line 2 6, an optical fiber collimator 1 7, an optical fiber collimator 2 8, a half-wave plate 1 9, a half-wave plate 2 10, a reflector 1 11, a dichroic mirror 1 12, a difference frequency crystal 1 13, a mid-infrared filter 14, a reflector 2 15, a reflector 3 16, a dichroic mirror 2 17, a 1062nm laser 18, a half-wave plate 3 19, a reflector 4 20, a difference frequency crystal 2 21, a near-infrared filter 22, an optical fiber collimator 3 23 and an avalanche photodiode 24.

[0024] The 1062nm mode-locked laser 2 and the 1553nm mode-locked laser 4 are the light sources of the system. The light emitted by the 1062nm mode-locked laser 2 is pump light, and it contains an optical power amplifier part inside, and its maximum output power is 5W. The light emitted by the 1553nm mode-locked laser 4 is signal light, and it contains two electro-optical modulators inside, one modulator is used to modulate the sine wave signal through the RF signal generator 1 in the active mode-locked structure cavity to output the mode-locked pulse; the other modulator is used to modulate information on the pulse light through the arbitrary waveform signal generator 3 when the mode-locked pulse light is output. At the same time, it contains an optical power amplifier part inside, and its maximum output power is 2W.

[0025] The signal rate emitted by the arbitrary waveform signal generator 3 should be the same as the repetition rate of the 1553nm mode-locked laser 4 .

[0026] The central wavelength of the half-wave plate 1 9 and the half-wave plate 3 19 is 1062 nm.

[0027] The central wavelength of the half-wave plate 10 is 1553 nm.

[0028] The 1062nm laser 18 is a continuous light laser, and its maximum output power is 5W.

[0029] The polarization period, thickness and length of the difference frequency crystal 1 13 and the difference frequency crystal 2 21 are consistent.

[0030] The central wavelength of the near infrared filter 22 is 1553 nm.

[0031] Near-infrared beam generation and signal modulation part: RF signal generator 1 inputs sine wave signals to 1062nm mode-locked laser 2 and 1553nm mode-locked laser 4 to ensure that the two lasers output the same repetition rate. At the same time, RF signal generator 1 inputs clock signals to arbitrary waveform signal generator 3 to ensure that the signal of arbitrary waveform signal generator 3 can be modulated on the pulse of signal light. Arbitrary waveform signal generator 3 is connected to 1553nm mode-locked laser 4 through RF line, and pseudo-random binary (PRBS) code is sent to 1553nm mode-locked laser 4. The transmission delay of arbitrary waveform signal generator 3 is adjusted to make the modulation signal accurately match the mode-locked pulse signal, such as Figure 2 As shown, the black dotted line is the PRBS code generated by the arbitrary waveform signal generator 3, and the black solid line is the active mode-locked pulse generated by the 1553nm mode-locked laser 4. Then, the modulator in the 1553nm mode-locked laser 4 is adjusted, as shown in FIG. Figure 3 As shown, when the mode-locked pulse sequence and the PRBS signal coincide in the time domain, the bias voltage of the modulator in the 1553nm mode-locked laser 4 is adjusted so that the PRBS signal is modulated on the mode-locked pulse sequence.

[0032] The output ends of the 1062nm mode-locked laser 2 and the 1553nm mode-locked laser 4 are connected to the optical fiber delay line 1 5 and the optical fiber delay line 2 6 through optical fibers, respectively. The optical fiber delay line 1 5 and the optical fiber delay line 2 6 are connected to the optical fiber collimator 1 7 and the optical fiber collimator 2 8, respectively. The pump light and the signal light pass through the optical fiber delay line 1 5 and the optical fiber delay line 2 6, respectively, and then output parallel light through the optical fiber collimator 1 7 and the optical fiber collimator 2 8.

[0033] Mid-infrared light beam generation and transmission part: The pump light is incident on the half-wave plate 19 in parallel, and the signal light is incident on the half-wave plate 2 10 in parallel. The half-wave plate 19 and the half-wave plate 2 10 respectively control the polarization direction of the pump light and the signal light output to meet the quasi-phase matching conditions required for the difference frequency. The pump light passes through the half-wave plate 19 and is incident on the reflector 11. After being reflected by the reflector 11, it is incident on the dichroic mirror 12, and then reflected by the dichroic mirror 12 and incident on the difference frequency crystal 13. The signal light is transmitted through the dichroic mirror 12 and then merged with the pump light. The merged light generates mid-infrared band conversion light through the difference frequency crystal 13. The mid-infrared band conversion light passes through the mid-infrared filter 14 to eliminate the residual pump light and signal light. Finally, the mid-infrared band conversion light is reflected by the reflector 2 15 and the reflector 3 16 in turn. The reflector 2 15 and the reflector 3 16 simulate free space.

[0034] The pump light and the signal light undergo a difference frequency effect after passing through the difference frequency crystal, and generate mid-infrared band conversion light. The central wavelength of the conversion light is about 3360nm. The spectrum of the mid-infrared conversion light is as shown in FIG. Figure 4 shown.

[0035] The receiving and signal demodulation part of the mid-infrared beam: the parallel light output by the 1062nm laser 18 is incident on the half-wave plate 3 19, and the polarization direction of the light is changed by the half-wave plate 3 19 to meet the quasi-phase matching conditions required by the difference frequency. After passing through the half-wave plate 3 19, the light beam is incident on the reflector 4 20, and then reflected by the reflector 4 20 and incident on the dichroic mirror 2 17, and then reflected by the dichroic mirror 2 17. The reflected light is combined with the mid-infrared band conversion light reflected by the reflector 3 16 and then transmitted by the dichroic mirror 2 17. The combined light is incident on the difference frequency crystal 2 21 to generate 1553nm near-infrared conversion light, and then the residual 1062nm light and mid-infrared band conversion light are eliminated by the near-infrared filter 22. The near-infrared conversion light is incident on the fiber collimator 3 23, and after passing through the fiber collimator 3 23, it is coupled into the optical fiber and transmitted to the avalanche photodiode 24, and the avalanche photodiode 24 performs photoelectric conversion and signal demodulation.

[0036] After demodulating the signal, measure the signal eye diagram, such as Figure 5 As shown, when the signal modulation rate is 10Gb / s, the optical signal-to-noise ratio of the demodulated signal is 11.92dB, and the large eye opening amplitude indicates that the system has a high noise tolerance and a large modulation depth. The present invention realizes high repetition rate output of mid-infrared converted light, which can meet the needs of mid-infrared high-speed optical communication.

Claims

1. A mid-infrared ultrashort pulse high-speed space laser communication system, characterized in that: The system comprises a radio frequency signal generator (1), a 1062 nm mode-locked laser (2), an arbitrary waveform signal generator (3), a 1553 nm mode-locked laser (4), a fiber delay line 1 (5), a fiber delay line 2 (6), a fiber collimator 1 (7), a fiber collimator 2 (8), a half-wave plate 1 (9), a half-wave plate 2 (10), a reflector 1 (11), a dichroic mirror 1 (12), a difference frequency crystal 1 (13), a mid-infrared filter (14), a reflector 2 (15), a reflector 3 (16), a dichroic mirror 2 (17), a 1062 nm laser (18), a half-wave plate 3 (19), a reflector 4 (20), a difference frequency crystal 2 (21), a near-infrared filter (22), a fiber collimator 3 (23) and an avalanche photodiode (24); The radio frequency signal generator (1) inputs a sine wave signal to the 1062nm mode-locked laser (2) and the 1553nm mode-locked laser (4), and at the same time the radio frequency signal generator (1) inputs a clock signal to the arbitrary waveform signal generator (3); the arbitrary waveform signal generator (3) is connected to the 1553nm mode-locked laser (4) by a radio frequency line, and sends a PRBS code to the 1553nm mode-locked laser (4); The output ends of the 1062nm mode-locked laser (2) and the 1553nm mode-locked laser (4) are respectively connected to an optical fiber delay line 1 (5) and an optical fiber delay line 2 (6) through optical fibers, and the optical fiber delay line 1 (5) and the optical fiber delay line 2 (6) are respectively connected to an optical fiber collimator 1 (7) and an optical fiber collimator 2 (8), and the pump light and the signal light respectively pass through the optical fiber delay line 1 (5) and the optical fiber delay line 2 (6), and then respectively output parallel light through the optical fiber collimator 1 (7) and the optical fiber collimator 2 (8); The pump light is incident on the half-wave plate 1 (9) in parallel, and the signal light is incident on the half-wave plate 2 (10) in parallel. The half-wave plate 1 (9) and the half-wave plate 2 (10) respectively control the polarization directions of the pump light and the signal light output; the pump light passes through the half-wave plate 1 (9) and is incident on the reflector 1 (11), and is reflected by the reflector 1 (11) and is incident on the dichroic mirror 1 (12), and is then reflected by the dichroic mirror 1 (12) and is incident on the difference frequency crystal 1 (13); the signal light is transmitted through the dichroic mirror 1 (12) and then merged with the pump light, and the merged light passes through the difference frequency crystal 1 (13) to generate mid-infrared band conversion light, and the mid-infrared band conversion light passes through the mid-infrared filter (14) to eliminate the residual pump light and signal light, and finally the mid-infrared band conversion light is reflected by the reflector 2 (15) and the reflector 3 (16) in turn; The parallel light output by the 1062nm laser (18) is incident on the half-wave plate three (19), and the polarization direction of the light is changed by the half-wave plate three (19). The light beam is incident on the reflector four (20) after passing through the half-wave plate three (19), and then is reflected by the reflector four (20) and incident on the dichroic mirror two (17), and then is reflected by the dichroic mirror two (17). The reflected light and the mid-infrared band reflected by the reflector three (16) and then transmitted by the dichroic mirror two (17) The converted light is combined, and the combined light is incident on the difference frequency crystal 2 (21) to generate 1553nm near-infrared converted light, and then the residual 1062nm light and mid-infrared band converted light are eliminated by the near-infrared filter (22); the near-infrared converted light is incident on the optical fiber collimator 3 (23), and after passing through the optical fiber collimator 3 (23), it is coupled into the optical fiber and transmitted to the avalanche photodiode (24), and the avalanche photodiode (24) performs photoelectric conversion and signal demodulation.

2. A mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The light emitted by the 1062nm mode-locked laser (2) is pump light and contains an optical power amplification part, and its maximum output power is 5W.

3. A mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The light emitted by the 1553nm mode-locked laser (4) is signal light, and contains two electro-optical modulators, one modulator is used to modulate a sine wave signal in an active mode-locked structure cavity through a radio frequency signal generator (1) to output a mode-locked pulse; the other modulator is used to modulate information on the pulse light through an arbitrary waveform signal generator (3) when the mode-locked pulse light is output; and the optical power amplification part is also contained inside, and its maximum output power is 2W.

4. A mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The signal rate emitted by the arbitrary waveform signal generator (3) should be the same as the repetition rate of the 1553nm mode-locked laser (4).

5. A mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The central wavelengths of the half-wave plate one (9) and the half-wave plate three (19) are 1062 nm.

6. A mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The central wavelength of the half-wave plate 2 (10) is 1553 nm.

7. A mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The 1062 nm laser (18) is a continuous light laser with a maximum output power of 5 W.

8. The mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The polarization period, thickness and length of the difference frequency crystal 1 (13) and the difference frequency crystal 2 (21) are consistent.

9. A mid-infrared ultrashort pulse high-speed space laser communication system according to claim 1, characterized in that: The central wavelength of the near-infrared filter (22) is 1553 nm.

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