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

Abstract

The application discloses a kind of based on self-imaging effect's tunable high-speed optical pulse generation system and method, the system includes the pulse light source, first adjustable optical delay line, intensity modulator, second adjustable optical delay line, phase modulator and dispersive medium connected in turn.Pulse light source outputs periodic optical pulse as input optical pulse, input optical pulse is input intensity modulator after first adjustable optical delay line, first signal generator inputs modulation signal to intensity modulator, modulates input optical pulse;Intensity modulated optical pulse then input phase modulator after second adjustable optical delay line, second signal generator inputs modulation signal to phase modulator, modulates input pulse;Phase modulated optical pulse passes through dispersive medium, realizes higher order number of fractional order self-imaging effect, and the repetition rate of optical pulse is multiplied.The application can output adjustable repetition rate high-speed optical pulse, and the difficulty of generating phase modulation signal is lower.

Description

TECHNICAL FIELD

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

[0002] Periodic optical pulse sequence has important application value in modern optics and communication fields, and is widely used in fiber communication, optical computing, material processing, biomedical molecular detection, ultrafast spectroscopy and other fields. Since there are strict requirements for the accuracy and stability of the periodic optical pulse sequence in these applications, how to accurately control the repetition rate of the repetitive pulse has become a key problem. Periodic optical pulse sequence is usually generated by mode-locked laser. 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 stability of the output.

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

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

[0005] To achieve the above objectives, the present invention employs the following technical solution: a tunable high-speed optical pulse generation system based on self-imaging effect, comprising a pulsed light source, a first tunable optical delay line, an intensity modulator, a second tunable optical delay line, a phase modulator, and a dispersive medium connected sequentially. Specifically, the pulsed light source outputs periodic optical pulses as the system's input optical pulses. The input optical pulses first pass through the first tunable optical delay line and are then input to the intensity modulator. A 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 pulses. The intensity-modulated optical pulses then pass through the second tunable optical delay line and are input to the phase modulator. A 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 pulses. Finally, the phase-modulated optical pulses pass through the dispersive medium, achieving a higher-order fractional-order self-imaging effect, and the repetition rate of the optical pulses is multiplied.

[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 light pulse output by the intensity modulator to simulate the characteristics of the light pulse 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 synchronized.

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

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

[0012] S1, The 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 a first adjustable optical delay line before being input to the intensity modulator. By adjusting 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, suppressing some pulses and retaining only one pulse out of n pulses, where n is a positive integer. The period of the output optical pulse of the intensity modulator becomes n times the period of the input optical pulse, i.e., nT. R .

[0014] S3, subsequently, the output light 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 in time to the light pulse sequence.

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

[0016] S5, the light pulse output by the phase modulator is passed through a fixed dispersion medium to realize a fractional order self-imaging effect of a higher order, the repetition rate of the light pulse is multiplied, and finally a high-speed light pulse sequence is output.

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

[0018] (1) In the present application, the amplitude and period controllable electrical modulation signal generated by the signal generator is used for the intensity modulator and the phase modulator under the condition that the experimental device is fixed, and finally a high-speed light pulse with adjustable speed is output.

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

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

[0021] Figure 1 Fig. 1 is a structural schematic diagram of a tunable high-speed optical pulse generation system based on self-imaging effect in an embodiment of the present application;

[0022] Fig. 2(a) is a schematic diagram of an input light pulse based on self-imaging effect in an embodiment of the present application;

[0023] Fig. 2(b) is a schematic diagram of an input light pulse and an intensity modulation signal of an intensity modulator based on self-imaging effect in an embodiment of the present application;

[0024] Fig. 2(c) is a schematic diagram of an input light pulse and a phase modulation signal of a phase modulator based on self-imaging effect in an embodiment of the present application;

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

[0026] Figure 1 In the middle: 1. Pulsed light source; 2. First tunable light delay line; 3. First signal generator; 4. Intensity modulator; 5. Second tunable light delay line; 6. Second signal generator; 7. Phase modulator; 8. Dispersive medium. Detailed Implementation

[0027] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0028] Example 1

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

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

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

[0032] S2, the intensity modulator modulates the input pulse sequence, suppresses part of the pulses, and only retains one pulse in n pulses, wherein n is a positive integer, and the period of the output light pulse of the intensity modulator becomes n times of the input light pulse, that is, nT R , so as to reduce the repetition rate of the pulse sequence.

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

[0034] S4, in the phase modulator, the input light pulse sequence is modulated according to the phase modulation signal, and the output pulse is simulated as a different order of fractional order self-imaging effect. In this process, the second signal generator generates a modulation electrical signal, and the voltage is represented as , wherein V πp is the half-wave voltage of the phase modulator, m is a positive integer, q=1, 2, …, m corresponds to the light pulse position, and the duration of each symbol of the rectangular electrical signal is nT R .

[0035] S5, the light pulse output by the phase modulator passes through the fixed dispersion medium, realizes a higher order of fractional order self-imaging effect, the repetition rate of the light pulse is multiplied, and finally a high-speed light pulse sequence is output.

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

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

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

[0039]

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

[0041]

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

[0043]

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

[0045]

[0046] The output optical pulse passes through the dispersion medium, and the position on the Talbot carpet moves a distance of ΔZ length, and the corresponding position of the output optical pulse on the Talbot carpet is:

[0047]

[0048] From the above formula, n 2 m+1 does not contain the factor n or m, which proves that n 2 m+1 and n 2 m 2 are relatively prime, so the output optical pulse is equivalent to passing through an n 2 m 2 order fractional Talbot self-imaging effect, and since the pulse period at the integer Talbot distance is nmT R , the period of the output optical pulse is:

[0049]

[0050] The period of the output light pulse is changed from the original The repetition rate is changed from the original nm times, so that the generation of high-speed output light pulse is realized.

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

[0052] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only preferred examples of the present application and are not intended to limit the present application. Various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended 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 pulsed light source, a first tunable optical delay line, an intensity modulator, a second tunable optical delay line, a phase modulator, and a dispersive medium connected in sequence; The pulsed light source outputs periodic light pulses as input light pulses. These input light pulses pass through a first adjustable optical delay line and are then input to an intensity modulator. A first signal generator, connected to the intensity modulator, 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 are input to a phase modulator. A second signal generator, connected to the phase modulator, inputs a modulation signal to the phase modulator to modulate the input light pulses. After phase modulation, the light pulses pass through a dispersive medium, achieving a higher-order fractional-order self-imaging effect, and the repetition rate of the light pulses is multiplied. The implementation process of the tunable high-speed optical pulse generation system based on the self-imaging effect is as follows: S1, The 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 to the intensity modulator. S2. The intensity modulator modulates the input pulse sequence, retaining only one pulse out of n pulses, where n is a positive integer. The period of the output optical pulse becomes n times the period of the input optical pulse, i.e., nT. R ; S3. The output optical pulses of the intensity modulator are passed through the second adjustable optical delay line so that each phase modulation signal corresponds to the optical pulse sequence in time, and then input 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 fractional self-imaging effects of different orders. During modulation, the second signal generator produces a modulated electrical signal, the voltage of which is expressed as... Among them, V πp The voltage 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 ; S5. The light pulses output by the phase modulator are passed through a fixed dispersion medium to achieve a higher-order fractional self-imaging effect, the repetition rate of the light pulses is multiplied, and finally the light pulse sequence is output.

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

4. The tunable high-speed optical pulse generation system based on self-imaging effect according to claim 1, characterized in that, The phase modulator simulates the characteristics of optical pulses 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 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 synchronized.

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

Images