Tunable high-speed optical pulse generation system and method based on self-imaging effect

Abstract

The invention discloses a tunable high-speed light pulse generation system and method based on a self-imaging effect. The system comprises a pulse light source, a first adjustable light delay line, an intensity modulator, a second adjustable light delay line, a phase modulator and a dispersive medium which are connected in sequence. The pulse light source outputs a periodic light pulse as an input light pulse, the input light pulse passes through the first adjustable light delay line and then is input into the intensity modulator, and the first signal generator inputs a modulation signal to the intensity modulator to modulate the input light pulse; the light pulse subjected to intensity modulation is input into the phase modulator through a second adjustable light delay line, a second signal generator inputs a modulation signal to the phase modulator, and the input pulse is modulated; the optical pulse after phase modulation passes through the dispersive medium, a higher-order fractional order self-imaging effect is achieved, and the repetition rate of the optical pulse is multiplied. According to the invention, the high-speed optical pulse with the adjustable repetition rate can be output, and the difficulty of generating the phase modulation signal is low.

Description

Technical Field

[0001] The invention belongs to the technical field of microwave photon signal processing, and in particular relates to a tunable high-speed optical pulse generation system and method based on a self-imaging effect. Background Art

[0002] Periodic optical pulse sequences have important application value in the field of modern optics and communications, and are widely used in fiber-optic communications, optical computing, material processing, biomedical molecular detection, ultrafast spectroscopy and many other fields. Since these applications have strict requirements on the accuracy and stability of periodic optical pulse sequences, how to accurately control the repetition rate of repeated pulses has become a key research issue. Periodic optical pulse sequences are usually generated by mode-locked lasers. In order to accurately control the pulse period, it is usually necessary to adjust the physical parameters of the laser cavity or use harmonic mode-locking technology. However, these methods are often limited by physical conditions, resulting in insufficient flexibility and poor output stability.

[0003] The pure phase signal processing method based on the theory of fractional self-imaging effect can achieve the output of high-speed optical pulses while keeping the characteristics of a single pulse undistorted through appropriate dispersion-induced spectral phase filtering. However, there is a clear correspondence between the repetition rate and dispersion of the output optical pulse. To achieve optical pulse output with different repetition rates, the dispersion amount needs to be changed, which limits the flexibility of the scheme. By using a combination of phase modulator and fixed dispersion, optical pulse output with different repetition rates can be achieved without changing the dispersion. However, with the increase of the optical pulse repetition rate, the complexity of the phase modulation signal increases significantly. In addition, the output of optical pulses with different repetition rates can also be achieved using an intensity modulator and fixed dispersion. However, with the increase of the optical pulse repetition rate, the number of retained input pulses decreases, resulting in a significant attenuation of the energy of the output optical pulse sequence. Therefore, how to balance the wide range of tunable pulse repetition rate and output optical pulse energy while increasing the optical pulse repetition rate is still an urgent problem to be solved. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention proposes a tunable high-speed optical pulse generation method and system based on the self-imaging effect. The system can flexibly adjust the repetition rate of the optical pulse, has the advantages of low modulation signal requirements and high output optical pulse energy.

[0005] In order to achieve the above-mentioned purpose, the technical scheme specifically adopted by the present invention is as follows: A tunable high-speed optical pulse generation system based on the self-imaging effect, comprising a pulse light source, a first adjustable optical delay line, an intensity modulator, a second adjustable optical delay line, a phase modulator and a dispersive medium connected in sequence. Specifically, the pulse light source outputs periodic optical pulses as the input optical pulses of the system. The input optical pulse first passes through the first adjustable optical delay line and then enters the intensity modulator. The first signal generator is connected to the intensity modulator and is used to input a modulation signal to the intensity modulator to modulate the input optical pulse. The intensity-modulated optical pulse then passes through the second adjustable optical delay line and enters the phase modulator. The second signal generator is connected to the phase modulator and is used to input a modulation signal to the phase modulator to modulate the input pulse. Finally, the phase-modulated optical pulse passes through the dispersive medium to achieve a higher-order fractional self-imaging effect, and the repetition rate of the optical pulse is doubled.

[0006] Furthermore, the intensity modulator performs periodic pulse selection on the input optical pulses to reduce the repetition rate of the optical pulses.

[0007] Furthermore, the phase modulator applies a specific phase waveform modulation to the optical pulse output by the intensity modulator to simulate the optical pulse characteristics generated by the fractional-order self-imaging effect.

[0008] Furthermore, the phase modulator can simulate the optical pulse characteristics generated by fractional-order self-imaging effects of different orders by changing the modulated phase waveform.

[0009] Furthermore, the first signal generator, the second signal generator and the pulse light source are kept synchronous.

[0010] Furthermore, the dispersive medium is one of a dispersion-compensating optical fiber or a chirped fiber grating, and the dispersion amount provided is fixed and is only related to the period of the input pulse.

[0011] The present invention also provides a method for generating tunable high-speed optical pulses based on the self-imaging effect, comprising the following steps:

[0012] S1, pulse light source output period is T R The optical pulse sequence is used as the input optical pulse of the system. The input optical pulse first passes through the first adjustable optical delay line and then enters the intensity modulator. Through the first adjustable optical delay line, it is ensured that each intensity modulation signal corresponds to the input optical pulse sequence in time.

[0013] S2. The intensity modulator modulates the input pulse sequence, suppresses some of the pulses, and retains only one pulse among n pulses, where n is a positive integer. The period of the intensity modulator output light pulse becomes n times that of the input light pulse, that is, nT R .

[0014] S3. Then, the output optical pulse of the intensity modulator is input into the phase modulator through the second adjustable optical delay line. By adjusting the second adjustable optical delay line, it is ensured that each phase modulation signal corresponds to the optical pulse sequence in time.

[0015] S4. In the phase modulator, the input optical pulse sequence is modulated according to the phase modulation signal to simulate the output pulses of different orders of fractional self-imaging effects. In this process, the second signal generator generates a modulated electrical signal, and the voltage is expressed as Among them, V πp is the half-wave voltage of the phase modulator, m is a positive integer, q=1,2,…,m corresponds to the position of the optical pulse, and the duration of each symbol of the rectangular electrical signal is nT R .

[0016] S5. Passing the optical pulse output by the phase modulator through a fixed dispersion medium to achieve a higher-order fractional self-imaging effect, double the repetition rate of the optical pulse, and finally output a high-speed optical pulse sequence.

[0017] The present invention has the following characteristics and beneficial effects:

[0018] (1) The present invention ensures that the experimental device remains unchanged, generates an amplitude and period controllable electrical modulation signal through a signal generator for an intensity modulator and a phase modulator, and finally outputs an adjustable rate high-speed optical pulse.

[0019] (2) Compared with a tunable high-speed optical pulse generation system based on a phase modulator and fixed dispersion, the phase modulation signal of the solution of the present invention has a longer period and a smaller amplitude, and the difficulty of generating a phase modulation signal is lower.

[0020] (3) Compared with the tunable high-speed optical pulse generation system based on intensity modulator and fixed dispersion, the scheme of the present invention can retain more input optical pulses, so the energy of the output optical pulses is higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of a tunable high-speed optical pulse generation system based on the self-imaging effect in an embodiment of the present invention;

[0022] FIG2( a ) is a schematic diagram of an input light pulse based on the self-imaging effect in an embodiment of the present invention;

[0023] FIG2( b ) is a schematic diagram of an optical pulse and an intensity modulation signal of an input intensity modulator based on a self-imaging effect in an embodiment of the present invention;

[0024] FIG2( c ) is a schematic diagram of an optical pulse and a phase modulation signal input to a phase modulator based on a self-imaging effect in an embodiment of the present invention;

[0025] FIG. 2( d ) is a schematic diagram of an output light pulse after dispersion based on the self-imaging effect in an embodiment of the present invention.

[0026] Figure 1 In: 1. Pulse light source; 2. First adjustable optical delay line; 3. First signal generator; 4. Intensity modulator; 5. Second adjustable optical delay line; 6. Second signal generator; 7. Phase modulator; 8. Dispersive medium. DETAILED DESCRIPTION

[0027] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0028] Example 1

[0029] like Figure 1 As shown, the present invention provides a tunable high-speed optical pulse generation system based on the self-imaging effect. The system includes a pulse light source 1 (Calamr), a first adjustable optical delay line 2 (General Photonics), an intensity modulator 4 (EOSPACE), a second adjustable optical delay line 5 (General Photonics), a phase modulator 7, and a dispersive medium 8, which are connected in sequence. The first signal generator 3 is connected to the RF modulation port of the intensity modulator, and the second signal generator 6 is connected to the RF modulation port of the phase modulator. When working, the pulse light source output period is T R The optical pulse sequence is input into the intensity modulator after passing through the first adjustable optical delay line 2. By adjusting the first adjustable optical delay line 2, it is ensured that the intensity modulation signal corresponds to the input optical pulse sequence in time. The first signal generator 3 inputs the modulation signal into the intensity modulator to modulate the input optical pulse. The output optical pulse of the intensity modulator is input into the phase modulator through the second adjustable optical delay line 5. By adjusting the second adjustable optical delay line 5, it is ensured that each phase modulation signal corresponds to the optical pulse sequence in time. The second signal generator 6 inputs the modulation signal into the phase modulator to modulate the input optical pulse. The optical pulse output by the phase modulator is passed through a fixed dispersion medium to achieve a higher-order fractional self-imaging effect, and the repetition rate of the optical pulse is doubled.

[0030] On the other hand, the present invention also provides a method for generating tunable high-speed optical pulses based on the self-imaging effect, comprising the following steps:

[0031] S1, pulse light source output period is T RThe optical pulse sequence is used as the input optical pulse of the system. The input optical pulse first passes through the first adjustable optical delay line and then enters the intensity modulator. Through the first adjustable optical delay line, it is ensured that each intensity modulation signal corresponds to the input optical pulse sequence in time to ensure synchronization in the subsequent modulation process.

[0032] S2. The intensity modulator modulates the input pulse sequence, suppresses some of the pulses, and retains only one pulse among n pulses, where n is a positive integer. The period of the intensity modulator output light pulse becomes n times that of the input light pulse, that is, nT R , thus reducing the repetition rate of the pulse sequence.

[0033] S3. Then, the output optical pulse of the intensity modulator is input into the phase modulator through the second adjustable optical delay line. By adjusting the second adjustable optical delay line, it is ensured that each phase modulation signal corresponds to the optical pulse sequence in time, so as to ensure synchronization in the subsequent modulation process.

[0034] S4. In the phase modulator, the input optical pulse sequence is modulated according to the phase modulation signal to simulate the output pulses of different orders of fractional self-imaging effects. In this process, the second signal generator generates a modulated electrical signal, and the voltage is expressed as Among them, V πp is the half-wave voltage of the phase modulator, m is a positive integer, q=1,2,…,m corresponds to the position of the optical pulse, and the duration of each symbol of the rectangular electrical signal is nT R .

[0035] S5. Passing the optical pulse output by the phase modulator through a fixed dispersion medium to achieve a higher-order fractional self-imaging effect, double the repetition rate of the optical pulse, and finally output a high-speed optical pulse sequence.

[0036] The working principle of the present invention is as follows:

[0037] First, the input light pulse period generated by the pulse light source is T R After passing through the intensity modulator, the function of the intensity modulator is to select only one pulse from n pulses. The corresponding rectangular electrical signal generated by the first signal generator 3 is Among them, V πi is the half-wave voltage of the intensity modulator, n is a positive integer, p=1,2,…,n corresponds to the pulse position. The time window corresponding to each modulation waveform is T R , the period of the output light pulse after the intensity modulator becomes n times the original, that is, nT R .

[0038] The output pulse of the intensity modulator enters the phase modulator. The function of the phase modulator is to simulate the input light pulse into an output pulse under the fractional self-imaging effect of different orders according to the input phase modulation signal. At this time, the rectangular electrical signal generated by the second signal generator 6 is Among them, V πp is the half-wave voltage of the phase modulator, m is a positive integer, q=1,…,m corresponds to the pulse position. The time window corresponding to each modulation waveform is nT R After modulation by the phase modulator, the output pulse is similar to the pulse through the m-order fractional self-imaging effect, and the pulse period at the integer Talbot distance on the Talbot carpet is nmT R , the integer Talbot distance is:

[0039]

[0040] Where β2 is the second-order dispersion constant, n, m are positive integers, T R is the input light pulse period generated by the pulse light source, and the corresponding position of the output pulse after the phase modulator on the Talbot carpet is:

[0041]

[0042] The output optical pulse of the phase modulator enters the dispersion compensation fiber. The dispersion amount is related to the input optical pulse period:

[0043]

[0044] The corresponding length on the Talbot carpet is:

[0045]

[0046] The output light pulse passes through the dispersive medium, which is equivalent to moving the position on the Talbot carpet by a distance of ΔZ. The corresponding position of the output light pulse in the Talbot carpet is:

[0047]

[0048] From the above formula, we can see that n 2 m+1 does not contain factors n or m, prove n 2 m+1 and n 2 m 2 Therefore, the output optical pulse is equivalent to passing through an n 2 m 2 The fractional self-imaging effect of the order is due to the pulse period at the integer Talbot distance being nmT. R , the period of the output light pulse is:

[0049]

[0050] Compared with the input optical pulse, the period of the output optical pulse is changed. Its repetition rate becomes nm times of the original one, thus realizing the generation of high-rate output light pulses.

[0051] exist Figure 1 In the verification of the system shown, the input optical pulse has a period of 100 ps. In order to achieve the self-imaging condition, the dispersion value of the dispersive medium is set to 1591.6 ps. 2 . The values ​​of n and m are both set to 2. Figure 2 shows the waveforms of optical pulses and modulated signals. Figure 2(a) shows the time domain waveform of the input optical pulse, Figure 2(b) shows the optical pulse and intensity modulated signal input to the intensity modulator, Figure 2(c) shows the optical pulse and phase modulated signal input to the phase modulator, and Figure 2(d) shows the output optical pulse after passing through the dispersive medium. The amplitude and time interval of the pulses are consistent with the theoretical results, proving the system's ability to generate tunable high-speed optical pulses.

[0052] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A tunable high-speed optical pulse generation system based on self-imaging effect, characterized in that: It includes a pulse light source, a first adjustable optical delay line, an intensity modulator, a second adjustable optical delay line, a phase modulator and a dispersion medium which are connected in sequence; The pulse light source outputs periodic light pulses as input light pulses. The input light pulses pass through a first adjustable optical delay line and then enter an intensity modulator. A first signal generator is connected to the intensity modulator and inputs a modulation signal to the intensity modulator to modulate the input light pulses. The intensity-modulated light pulses then pass through a second adjustable optical delay line and then enter a phase modulator. A second signal generator is connected to the phase modulator and inputs a modulation signal to the phase modulator to modulate the input light pulses. The phase-modulated light pulses pass through a dispersive medium to achieve a higher-order fractional self-imaging effect, and the repetition rate of the light pulses is doubled.

2. The tunable high-speed optical pulse generation system based on the self-imaging effect according to claim 1, characterized in that: The intensity modulator performs periodic pulse selection on the input optical pulses to reduce the repetition rate of the optical pulses.

3. The tunable high-speed optical pulse generation system based on the self-imaging effect according to claim 1, characterized in that: The phase modulator applies phase waveform modulation to the light pulse output by the intensity modulator to simulate the light pulse characteristics generated by the fractional-order self-imaging effect.

4. The tunable high-speed optical pulse generation system based on the self-imaging effect according to claim 1, characterized in that: The phase modulator simulates the optical pulse characteristics generated by fractional-order self-imaging effects of different orders by changing the modulated phase waveform.

5. The tunable high-speed optical pulse generation system based on the self-imaging effect according to claim 1, characterized in that: The first signal generator, the second signal generator and the pulse light source are kept synchronous.

6. The tunable high-speed optical pulse generation system based on the self-imaging effect according to claim 1, characterized in that: The dispersive medium is one of a dispersion compensating optical fiber or a chirped optical fiber grating, and the dispersion amount provided is fixed and only related to the period of the input pulse.

7. A method for generating tunable high-speed optical pulses based on self-imaging effect, used to implement the tunable high-speed optical pulse generation system according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1, pulse light source output period is T R The optical pulse sequence is used as the input optical pulse, the input optical pulse passes through the first adjustable optical delay line so that each intensity modulation signal corresponds to the input optical pulse sequence in time, and then is input into the intensity modulator; S2. The intensity modulator modulates the input pulse sequence, retaining only one pulse among n pulses, where n is a positive integer. The period of the intensity modulator output light pulse becomes n times that of the input light pulse, i.e. nT R ; S3, passing the output optical pulse of the intensity modulator through a second adjustable optical delay line so that each phase modulation signal corresponds to the optical pulse sequence in time, and then inputting the output optical pulse of the intensity modulator into the phase modulator; S4, in the phase modulator, the input optical pulse sequence is modulated according to the phase modulation signal to simulate the output pulses of the fractional self-imaging effect of different orders; S5. Passing the optical pulse output by the phase modulator through a fixed dispersion medium to achieve a higher-order fractional self-imaging effect, multiply the repetition rate of the optical pulse, and finally output an optical pulse sequence.

8. The method for generating tunable high-speed optical pulses based on the self-imaging effect according to claim 7, characterized in that: In step S4, the second signal generator generates a modulated electrical signal, and the voltage is expressed as Among them, V πp is the half-wave voltage of the phase modulator, m is a positive integer, q=1,2,…,m corresponds to the position of the optical pulse, and the duration of each symbol of the rectangular electrical signal is nT R .

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