Optical pulse frequency doubling method and device based on dispersion effect

Abstract

The invention discloses an optical pulse frequency doubling method based on a dispersion effect. Phase modulation or intensity modulation is carried out on the optical pulse sequence to be subjected to frequency multiplication with the repetition period being T0, wherein the loading signal of the phase modulation is # imgabs0 #, and the loading signal expression of the intensity modulation is # imgabs1 # # imgabs2 # represents down rounding operation; and carrying out dispersion treatment with the dispersion amount of # imgabs3 # on the generated modulation optical signal, n being a non-negative integer, and thus obtaining a frequency multiplication optical pulse sequence with a frequency multiplication factor # imgabs4 #. The invention further discloses an optical pulse frequency doubling device based on the dispersion effect. Compared with the prior art, the non-integer multiple frequency multiplication of the optical pulse can be realized, the frequency multiplication factor is easy to adjust, a complex optical interference structure is not needed, power balance and time delay matching are not needed, the system is simple, and the stability is high.

Description

Technical Field

[0001] The present invention relates to a method for doubling the frequency of optical pulses. Background Art

[0002] Due to the advantages of a large number of carriers, consistent frequency intervals, and good coherence in optical pulse sequences, optical pulse sequences with different repetition frequencies play a crucial role in various applications, including fiber optic radio links, optical computing, optical sensing, optical communication, etc. There are many existing methods for generating optical pulse sequences, such as passive mode-locking technology, active mode-locking technology, and modulator-based technology. The first two methods already have related commercial products; however, the optical pulse sequences generated by passive mode-locking lasers usually have a relatively low repetition frequency and are not adjustable, and each passive mode-locking laser can only generate optical pulse sequences with a single repetition frequency. Although the repetition frequency of the optical pulse sequences generated by active mode-locking lasers can be adjusted, it is often difficult to adjust, the output is also unstable, and the repetition frequency is limited by the bandwidth of electronic devices. The modulator-based technology is a common method for generating pulse signals with different repetition frequencies, but the repetition frequency of the optical pulse sequences generated by this method is also limited by the bandwidth of electronic devices.

[0003] Existing optical pulse repetition frequency doubling technologies include the method based on Mach-Zehnder interferometers (S. Sharma and S. Roy. Design of all-optical parallel multipliers using semiconductor optical amplifier-based Mach–Zehnder interferometers[J] J. Supercomput., 2021, 77(7): p. 7315-7350.), the principle of which is to divide the optical pulse signal into multiple paths with equal optical signal power for each path. After introducing a certain delay in each path, these multiple paths of optical signals are recombined into one path, and the newly combined optical signal is the optical pulse sequence after doubling the repetition frequency. Theoretically, this method can achieve frequency doubling of any integer multiple of the repetition frequency. However, in practical applications, this method faces two major challenges: one is that the difficulty of evenly dividing the optical power increases significantly as the frequency doubling factor increases (the number of optical paths increases), and the other is that the accuracy of delay matching between paths requires increasingly strict as the frequency doubling factor increases, resulting in limited scalability of the system. In addition, this method is only applicable to integer multiple frequency doubling, and there is still a technical gap for the need of non-integer multiple repetition frequency regulation.

[0004] Therefore, exploring an optical pulse frequency doubling method that can adjust the frequency doubling factor, especially achieving non-integer multiple frequency doubling, has important research value and application prospects. Summary of the Invention

[0005] The object of the present invention is to overcome the deficiencies existing in the existing optical pulse frequency doubling technology, and provide an optical pulse frequency doubling method based on the dispersion effect, which can realize non-integer multiple frequency doubling of optical pulses, the frequency doubling factor is easy to adjust, and there is no need for a complex optical interference structure, no need for power equalization and time delay matching, the system is simple and has high stability.

[0006] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0007] An optical pulse frequency doubling method based on the dispersion effect, which performs phase modulation or intensity modulation on an optical pulse sequence to be frequency doubled with a repetition period of T0. The loading signal for phase modulation is: The loading signal for intensity modulation is: represents the floor operation; perform dispersion processing with a dispersion amount of on the generated modulated optical signal, where n is a non-negative integer, and then a frequency doubled optical pulse sequence with a frequency doubling factor of is obtained.

[0008] Based on the same inventive concept, the following technical solutions can also be obtained:

[0009] An optical pulse frequency doubling device based on the dispersion effect, comprising:

[0010] A modulation module, which is used to perform phase modulation or intensity modulation on an optical pulse sequence to be frequency doubled with a repetition period of T0. The loading signal for phase modulation is: The loading signal for intensity modulation is: represents the floor operation;

[0011] A dispersion module, which is used to perform dispersion processing with a dispersion amount of on the generated modulated optical signal, where n is a non-negative integer, and then a frequency doubled optical pulse sequence with a frequency doubling factor of is obtained.

[0012] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0013] The present invention uses the dispersion effect to realize the frequency doubling of optical pulses, supports the realization of non-integer multiple frequency doubling (n + 1 / 2 frequency doubling), and improves the flexibility of frequency doubling; the present invention first applies a periodic electrical signal to the modulator to perform phase modulation or intensity modulation on the optical pulse sequence, and then obtains the frequency doubled optical pulse signal through the dispersion effect, without a complex optical interference structure, without the need for power equalization and time delay matching, the system is simpler and has high stability; the present invention supports both phase modulation and intensity modulation, enhancing the compatibility of the system. Description of the Drawings

[0014] Figure 1Schematic diagram of the test device used for verifying the technical effects of the present invention;

[0015] Figure 2 Schematic diagram of experimental results, where (a) to (e) are schematic diagrams of the initial optical pulse signal, modulation signal, and optical pulse signals after frequency doubling by 1 / 2, 3 / 2, and 5 / 2 times in sequence;

[0016] Figure 3 Electrical signals applied to the modulator under different frequency doubling factors;

[0017] Figure 4 Time-domain comparison diagram before and after frequency doubling by 1 / 2;

[0018] Figure 5 Time-domain comparison diagram before and after frequency doubling by 3 / 2;

[0019] Figure 6 Time-domain comparison diagram before and after frequency doubling by 5 / 2. Specific implementation manners

[0020] Aiming at the deficiencies of the prior art, the idea of the present invention is to first apply an electrical signal with a specific structure to the modulator to perform phase modulation or intensity modulation on the optical pulse sequence, and then obtain the frequency-doubled optical pulse signal through the dispersion effect. There is no need for a complex optical interference structure, no need for power equalization and delay matching, the system is simple, and the stability is high.

[0021] The present invention specifically adopts the following technical solutions to solve the above technical problems:

[0022] An optical pulse frequency doubling method based on the dispersion effect, which performs phase modulation or intensity modulation on an optical pulse sequence to be frequency doubled with a repetition period of T0. The loading signal for phase modulation is: The loading signal for intensity modulation is: represents the floor function operation; perform dispersion processing with a dispersion amount of on the generated modulated optical signal, where n is a non-negative integer, that is, obtain an optical pulse sequence with a frequency doubling factor of .

[0023] Based on the same inventive concept, the following technical solutions can also be obtained:

[0024] An optical pulse frequency doubling device based on the dispersion effect, comprising:

[0025] A modulation module, configured to perform phase modulation or intensity modulation on an optical pulse sequence to be frequency doubled with a repetition period of T0. The loading signal for phase modulation is: The loading signal for intensity modulation is: represents the floor function operation;

[0026] A dispersion module is used to perform dispersion processing on the generated modulated optical signal with a dispersion amount of , where n is a non - negative integer, and thus the frequency - doubling factor of the frequency - doubled optical pulse sequence is obtained.

[0027] For the convenience of public understanding, the technical solution of the present invention will be described in detail below through an effect verification example and in combination with the accompanying drawings:

[0028] The structure of the effect verification test device adopted in this example is as Figure 1 shown, and it includes an optical pulse generation module, an arbitrary waveform generator, a phase modulator, and a dispersion module; the optical pulse sequence to be frequency - doubled generated by the optical pulse generation module is modulated by a specific electrical signal generated by the arbitrary waveform generator in the phase modulator. After the modulated optical signal passes through a dispersion medium that meets specific conditions, an optical pulse signal with successful frequency doubling can be obtained after the dispersion module.

[0029] Suppose the optical pulse signal to be frequency - doubled input is:

[0030]

[0031] where P is the peak power of each pulse, and T0 is the repetition time interval between pulses.

[0032] Then the intensity of the optical pulse signal to be frequency - doubled input is:

[0033] A in (t)=|E in (t)| 2 (2)

[0034] The electrical signal loaded onto the phase modulator is:

[0035]

[0036] Then the signal after phase modulation is:

[0037]

[0038] The dispersion amount of the dispersion medium is:

[0039]

[0040] where n is a non - negative integer, m is the frequency - doubling factor,

[0041] The transfer function of the dispersion medium is:

[0042]

[0043] Combining equations (1) to (6), the intensity of the frequency-doubled optical pulse signal can be obtained as follows:

[0044]

[0045] As can be seen from equation (7), this scheme can achieve frequency doubling. When n = 0, Dispersion amount The modulation signal is Then, when the modulated optical pulse sequence passes through the dispersion module, the output optical signal is the 1 / 2 frequency-doubled signal of the optical pulse to be frequency-doubled. When n = 1, Dispersion amount The modulation signal is Then, when the modulated optical pulse sequence passes through the dispersion module, the output optical signal is the 3 / 2 frequency-doubled signal of the optical pulse to be frequency-doubled. When n = 2, Dispersion amount The modulation signal is Then, when the modulated optical pulse sequence passes through the dispersion module, the output optical signal is the 5 / 2 frequency-doubled signal of the optical pulse to be frequency-doubled, and so on.

[0046] That is to say, when Dispersion amount The modulation signal is At this time, when the modulated optical pulse sequence passes through the dispersion module, the output optical signal is the Frequency-doubled signal of the optical pulse to be frequency-doubled.

[0047] Similarly, if the phase modulator is replaced with an intensity modulator, then when Dispersion amount The modulation signal is At this time, when the modulated optical pulse sequence passes through the dispersion module, the output optical signal is the Frequency-doubled signal of the optical pulse to be frequency-doubled. For the sake of brevity, the formula derivation part is omitted here.

[0048] Based on Figure 1 The test device shown in the figure is used for simulation verification. The frequency doubling factor is selected for simulation. The repetition frequency of the initial optical pulse sequence is set to 10 GHz, that is, T0 = 100 ps. The initial optical pulse sequence is as shown in Figure 2 (a) in the figure, and the corresponding periodic phase modulation signal is as shown in Figure 2 (b) in the figure. The dispersion amounts corresponding to different frequency doubling factors are 1061 ps 2 , 636.6 ps 2 , etc. After the modulated optical pulse signal passes through the dispersion module, the frequency-doubled optical pulse signal is obtained, and the result is as shown in Figure 2as shown in (c) - (e) therein.

[0049] In order to further verify the effect of the technical solution of the present invention, since only the dispersion compensation fiber with a dispersion amount of about 1460 ps 2 can be used in the experiment, the initial repetition frequency of the optical pulse sequence is determined according to the frequency doubling factor and the dispersion amount, which are 14.78 GHz, 8.54 GHz and 6.6 GHz respectively. According to different initial repetition frequencies, the period of the periodic phase modulation signal is different. The phase signals generated by an arbitrary waveform generator in the experiment are as Figure 3 shown. Figure 3 from top to bottom therein corresponding to the frequency doubling factors The repetition frequencies of the frequency - doubled optical pulse signals are 7.39 GHz, 12.81 GHz and 16.5 GHz respectively. The experimental results are as Figures 4 to 6 shown. Figure 4 Corresponding to the experimental results of the frequency doubling factor the dotted line is the initial optical pulse sequence, and the solid line is the frequency - doubled optical pulse sequence. Figure 5 Corresponding to the experimental results of the frequency doubling factor of the experimental results. Figure 6 Corresponding to the experimental results of the frequency doubling factor From the experimental results, it can be seen that the optical pulse sequence has successfully achieved frequency doubling of 1 / 2, 3 / 2, and 5 / 2.

[0050] In summary, the present invention can achieve frequency doubling of the optical pulse sequence based on the dispersion effect. Compared with the existing frequency doubling method based on Mach - Zehnder interferometer, the present invention does not require a complex optical interference structure, does not require power equalization and delay matching, the system is simpler and has high stability; the present invention supports phase modulation and intensity modulation, enhancing the compatibility of the system. In addition, the present invention can achieve non - integer - multiple frequency doubling of the optical pulse sequence repetition frequency, can achieve any (n + 1 / 2) - fold frequency doubling, and can be widely applied to fields such as microwave photonic links and optical communication systems.

Claims

1. A method for optical pulse frequency doubling based on the dispersion effect, characterized in that, Perform phase modulation or intensity modulation on the optical pulse sequence to be frequency-doubled with a repetition period of T0. The loading signal for phase modulation is: The loading signal for intensity modulation is: denotes the floor operation; perform dispersion processing on the generated modulated optical signal with a dispersion amount of where n is a non-negative integer, and thus obtain an optical pulse sequence with a frequency-doubling factor of .

2. An optical pulse frequency doubling device based on the dispersion effect, characterized in that, Including: A modulation module, configured to perform phase modulation or intensity modulation on an optical pulse sequence to be frequency - doubled with a repetition period of T0. The loading signal for phase modulation is: The loading signal for intensity modulation is: denotes the floor operation; A dispersion module, which is used to perform dispersion processing on the generated modulated optical signal with a dispersion amount of , where n is a non-negative integer, so as to obtain a frequency-doubled optical pulse sequence with a frequency-doubling factor of .

Images