Method and apparatus for generating an optical frequency comb based on brillouin scattering and electro-optic modulator

Abstract

The application discloses a method and device for generating an optical frequency comb based on Brillouin scattering and an electro-optic modulator, and belongs to the field of photoelectric measurement. The method comprises the following steps: a first laser and a second laser are used to generate pump light and seed light respectively, a multi-wavelength pump light is generated through a cascaded electro-optic modulator, the two lights are injected into a Sagnac loop circuit, an optical frequency comb is output through a fiber forward Brillouin scattering effect and an electro-optic modulator, and a polarization controller is adjusted to optimize the polarization state matching of the pump light and the seed light, so that the Brillouin scattering effect reaches a maximum value. The device is composed of a laser, an electro-optic modulator, a signal generator, an optical amplifier, an optical isolator, an optical coupler, a polarization controller and an optical fiber. The application combines the fiber forward Brillouin scattering effect and the electro-optic modulator, generates an optical frequency comb with wide spectrum and narrow interval, and can accurately control the comb tooth interval of the optical frequency comb through independent adjustment of the signal generator frequency, so that accurate measurement of signals or objects is realized.

Description

Technical Field

[0001] This invention relates to the field of photoelectric measurement, and more particularly to a method and apparatus for generating an optical frequency comb based on Brillouin scattering and an electro-optic modulator. Background Technology

[0002] As optical frequency comb technology develops towards wider spectrum and narrower spacing, it has shown unique advantages in fields such as high-precision spectral analysis, multi-channel optical communication, and super-resolution imaging. However, existing optical frequency comb systems still face the following technical challenges in achieving wide spectrum and narrow spacing output. (1) Traditional mode-locked lasers are limited by gain bandwidth and cannot simultaneously achieve ultra-wide spectrum coverage and narrow comb spacing. They need to rely on multi-level nonlinear frequency conversion to spread the spectrum, which leads to a surge in system complexity. (2) Ultra-dense combs (spacing less than 100MHz) are prone to mode competition and phase noise accumulation. Existing phase-locking technology is difficult to maintain comb phase stability over a wide spectrum. (3) When spreading the spectrum in nonlinear fibers or crystals, effects such as four-wave mixing and self-phase modulation can lead to non-uniform comb power and spectral distortion. Especially under narrow spacing conditions, crosstalk between adjacent combs is significantly aggravated. (4) Traditional dispersion compensation technology is difficult to optimize group velocity dispersion and nonlinear effects under a wide spectrum at the same time, which limits the efficiency of spectrum spreading.

[0003] Therefore, designing a method and device for generating optical frequency combs that balances wide spectrum and narrow spacing, while simultaneously achieving tunability and controllability in optical frequency comb generation, is a core challenge that urgently needs to be addressed in this field. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method and apparatus for generating an optical frequency comb based on Brillouin scattering and an electro-optic modulator. By combining the forward Brillouin scattering effect of optical fiber with an electro-optic modulator, a wide-spectrum, narrow-interval optical frequency comb is generated. By changing the frequency of the signal generator, the spacing of the optical frequency comb teeth can be continuously and precisely adjusted, enabling accurate measurement of signals or objects.

[0005] A method for generating an optical frequency comb based on Brillouin scattering and an electro-optic modulator includes the following steps:

[0006] Step S1: Use the first laser and the second laser to generate pump light and seed light respectively;

[0007] Step S2: The first laser is cascaded with the first electro-optic modulator and the second electro-optic modulator to modulate the pump light in step S1 into multi-wavelength pump light.

[0008] Step S3: Amplify the multi-wavelength pump light in step S2 using an optical fiber amplifier so that the Brillouin scattering of the multi-wavelength pump light reaches the threshold for Brillouin scattering in the optical fiber. Ensure unidirectional transmission of the multi-wavelength pump light using an optical isolator.

[0009] Step S4: The seed light from step S1 is processed by the second polarization controller, and the processed seed light and the multi-wavelength pump light that passed through the optical isolator in step S3 are injected into the Sagnac loop circuit composed of the first optical coupler, the second optical coupler, the first polarization controller and the optical fiber.

[0010] Step S5: Through the forward Brillouin scattering effect of the optical fiber, an optical frequency comb composed of multi-wavelength seed light and multi-wavelength pump light is output at the second optical coupler.

[0011] Step S6: Adjust the first polarization controller and the second polarization controller to optimize the polarization state matching between the pump light and the seed light, so that the Brillouin scattering effect reaches its maximum value.

[0012] Furthermore, in step S1, the pump light is used to excite the forward Brillouin scattering effect inside the optical fiber, and the seed light is used to perform phase modulation through the already excited forward Brillouin scattering effect, replicating the comb teeth and frequency spacing of the pump light.

[0013] Furthermore, in step S2, the driving signal of the first electro-optic modulator is a cosine signal with frequency f output by the first signal generator, and the magnitude of frequency f is equal to the Ro of the forward Brillouin scattering. 0,m The resonant frequency of the acoustic mode is determined by the number of comb teeth N generated by the first electro-optic modulator with the same power, and the driving signal of the second electro-optic modulator is a cosine signal with a frequency N times f output by the second signal generator.

[0014] In addition, the present invention also provides an optical frequency comb generating device based on Brillouin scattering and an electro-optic modulator, the optical frequency comb generating device based on Brillouin scattering and an electro-optic modulator comprising: a first laser, a second laser, a first electro-optic modulator, a second electro-optic modulator, a first signal generator, a second signal generator, an optical fiber amplifier, an optical isolator, a first optical coupler, a second optical coupler, a first polarization controller, a second polarization controller, and an optical fiber.

[0015] Furthermore, the first laser and the second laser are narrow-linewidth semiconductor lasers.

[0016] Furthermore, the first optical coupler is a 1×2 optical coupler, and the second optical coupler is a 2×2 optical coupler.

[0017] Furthermore, the optical fiber is an optical fiber with a forward Brillouin scattering coefficient greater than 3 at 100 MHz.

[0018] Furthermore, the first electro-optic modulator and the second electro-optic modulator are cascaded to form a cascaded electro-optic modulator, wherein the first electro-optic modulator is a Mach-Zehnder modulator and the second electro-optic modulator is a dual parallel Mach-Zehnder modulator.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0020] (1) This invention combines the forward Brillouin scattering effect of optical fiber with a cascaded electro-optic modulator, uses a signal generator to drive the modulator to generate multi-wavelength pump light, and uses a Sagnac loop to splice the multi-wavelength seed light and pump light to generate an optical frequency comb with a coverage range of over 10 GHz and a frequency interval of the Brillouin scattering resonance frequency, thus breaking through the gain bandwidth limitation of traditional mode-locked lasers.

[0021] (2) By independently adjusting the frequency of the signal generator, the present invention can accurately control the spacing of the optical comb teeth, solve the problems of the non-adjustable comb spacing and phase noise accumulation in the traditional technology, realize the continuous adjustability of the comb spacing and the optimization of phase stability, and the solution is easy to implement, low in cost and low in power consumption.

[0022] (3) The present invention adopts a highly nonlinear optical fiber and a Sagnac ring structure, and utilizes the linear phase modulation characteristics of Brillouin scattering to avoid the nonlinear effects such as four-wave mixing that cause uneven comb power and spectral distortion. Compared with the traditional nonlinear spread spectrum scheme, the spectral flatness is improved and the comb power consistency is significantly improved. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the optical frequency comb generating device based on Brillouin scattering and electro-optic modulator of the present invention;

[0024] Figure 2 The spectrum of the multi-wavelength pump source after electro-optic modulator and dual parallel Mach-Zehnder modulation is shown.

[0025] Figure 3 This is the optical frequency comb spectrum diagram after splicing together a multi-wavelength seed light source and a multi-wavelength pump light source. Detailed Implementation

[0026] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings. The technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] A method for generating an optical frequency comb based on Brillouin scattering and an electro-optic modulator includes the following steps:

[0028] Step S1: Use the first laser and the second laser to generate pump light and seed light respectively;

[0029] The pump light has a center wavelength of 1550.290 nm, a linewidth of 5 kHz, and a power of 16 dBm.

[0030] The center wavelength of the seed light is 1550.309 nm, the linewidth is 5 kHz, and the power is 10 dBm;

[0031] Step S2: The first laser is cascaded with the first electro-optic modulator and the second electro-optic modulator to modulate the pump light in step S1 into multi-wavelength pump light.

[0032] The first electro-optic modulator generates three comb teeth of equal power, which are connected to a first signal generator with a frequency of 129.5 MHz. This frequency is related to R. 0,3 The acoustic modes have the same resonant frequency; the second electro-optic modulator is connected to a 388.5MHz radio frequency signal source, i.e., the second signal generator. The spectrum of the modulated multi-wavelength pump source is shown below. Figure 2 As shown.

[0033] Step S3: Amplify the multi-wavelength pump light in step S2 using an optical fiber amplifier so that the Brillouin scattering of the multi-wavelength pump light reaches the threshold for Brillouin scattering in the optical fiber. Ensure unidirectional transmission of the multi-wavelength pump light using an optical isolator.

[0034] Step S4: The seed light from step S1 is processed by the second polarization controller, and the processed seed light and the multi-wavelength pump light that passed through the optical isolator in step S3 are injected into the Sagnac loop circuit composed of the first optical coupler, the second optical coupler, the first polarization controller and the optical fiber.

[0035] Step S5: Through the forward Brillouin scattering effect of the optical fiber, an optical frequency comb composed of multi-wavelength seed light and multi-wavelength pump light is output at the second optical coupler.

[0036] The splicing between the multi-wavelength seed light and the multi-wavelength pump light needs to take into account the frequency difference and comb teeth between the two lasers. The laser wavelengths used here are reasonable values ​​after multiple adjustments.

[0037] Step S6: Adjust the first polarization controller and the second polarization controller to optimize the polarization state matching between the pump light and the seed light, so that the Brillouin scattering effect reaches its maximum value.

[0038] Furthermore, in step S1, the pump light is used to excite the forward Brillouin scattering effect inside the optical fiber. The interaction between the forward Brillouin scattering and the seed light can achieve energy and phase transfer through stimulated scattering. The spectral characteristics of the pump light are assigned to the seed light, which is then used to perform phase modulation through the excited forward Brillouin scattering effect, replicating the comb teeth and frequency spacing of the pump light.

[0039] Furthermore, in step S2, the driving signal of the first electro-optic modulator is a cosine signal with frequency f output by the first signal generator, and the magnitude of frequency f is equal to the Ro of the forward Brillouin scattering. 0,m The resonant frequency of the acoustic mode is determined by the number of comb teeth N generated by the first electro-optic modulator with the same power, and the driving signal of the second electro-optic modulator is a cosine signal with a frequency N times f output by the second signal generator.

[0040] In addition, the present invention also provides an optical frequency comb generating device based on Brillouin scattering and an electro-optic modulator, such as... Figure 1 As shown, the optical frequency comb generating device based on Brillouin scattering and electro-optic modulator includes: a first laser, a second laser, a first electro-optic modulator, a second electro-optic modulator, a first signal generator, a second signal generator, an optical fiber amplifier, an optical isolator, a first optical coupler, a second optical coupler, a first polarization controller, a second polarization controller, and an optical fiber.

[0041] Furthermore, the first laser and the second laser are narrow-linewidth semiconductor lasers.

[0042] Furthermore, the first optical coupler is a 1×2 optical coupler, and the second optical coupler is a 2×2 optical coupler.

[0043] Furthermore, the optical fiber is an optical fiber with a forward Brillouin scattering coefficient greater than 3 at 100 MHz.

[0044] Furthermore, the first electro-optic modulator and the second electro-optic modulator are cascaded to form a cascaded electro-optic modulator, wherein the first electro-optic modulator is a Mach-Zehnder modulator and the second electro-optic modulator is a dual parallel Mach-Zehnder modulator.

[0045] Furthermore, a suitable electro-optic modulator is added to the cascaded electro-optic modulator to align the power near the center wavelength, thereby increasing its flatness.

[0046] Furthermore, the frequency interval of the pump light is the peak resonance frequency of the forward stimulated Brillouin scattering in the optical fiber.

[0047] The optical fiber used in this embodiment of the invention is HNLF single-mode fiber, with a length of 100km and an overall fiber loss of approximately 2dB. This device generates an optical frequency comb with a coverage exceeding 6GHz and a frequency spacing of 129.5MHz through a combination of a laser, an electro-optic modulator, and optical fiber. The result is as follows... Figure 3 As frequency spacing increases, frequency coverage will continue to expand. Currently, 6GHz is sufficient to cover the needs of most manufacturers and measurement services.

[0048] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for generating an optical frequency comb based on Brillouin scattering and an electro-optic modulator, characterized in that, Includes the following steps: Step S1: Use the first laser and the second laser to generate pump light and seed light respectively; Step S2: The first laser is cascaded with the first electro-optic modulator and the second electro-optic modulator to modulate the pump light in step S1 into multi-wavelength pump light. Step S3: Amplify the multi-wavelength pump light in step S2 using an optical fiber amplifier so that the Brillouin scattering of the multi-wavelength pump light reaches the threshold for Brillouin scattering in the optical fiber. Ensure unidirectional transmission of the multi-wavelength pump light using an optical isolator. Step S4: The seed light from step S1 is processed by the second polarization controller, and the processed seed light and the multi-wavelength pump light that passed through the optical isolator in step S3 are injected into the Sagnac loop circuit composed of the first optical coupler, the second optical coupler, the first polarization controller and the optical fiber. Step S5: Through the forward Brillouin scattering effect of the optical fiber, an optical frequency comb composed of multi-wavelength seed light and multi-wavelength pump light is output at the second optical coupler. Step S6: Adjust the first polarization controller and the second polarization controller to optimize the polarization state matching between the pump light and the seed light, so that the Brillouin scattering effect reaches its maximum value.

2. The optical frequency comb generation method based on Brillouin scattering and electro-optic modulator according to claim 1, characterized in that, In step S1, the pump light is used to excite the forward Brillouin scattering effect inside the optical fiber, and the seed light is used to perform phase modulation through the excited forward Brillouin scattering effect to replicate the comb teeth and frequency spacing of the pump light.

3. The optical frequency comb generation method based on Brillouin scattering and electro-optic modulator according to claim 1, characterized in that, In step S2, the driving signal of the first electro-optic modulator is a cosine signal with frequency f output from the first signal generator, and the magnitude of frequency f is equal to the Ro of the forward Brillouin scattering. 0,m The resonant frequency of the acoustic mode is determined by the number of comb teeth N generated by the first electro-optic modulator with the same power, and the driving signal of the second electro-optic modulator is a cosine signal with a frequency N times f output by the second signal generator.

4. An optical frequency comb generating device based on Brillouin scattering and an electro-optic modulator, characterized in that, The optical frequency comb generating device based on Brillouin scattering and electro-optic modulator is applied to the optical frequency comb generating method based on Brillouin scattering and electro-optic modulator as described in any one of claims 1-3. The optical frequency comb generating device based on Brillouin scattering and electro-optic modulator includes: a first laser, a second laser, a first electro-optic modulator, a second electro-optic modulator, a first signal generator, a second signal generator, an optical fiber amplifier, an optical isolator, a first optical coupler, a second optical coupler, a first polarization controller, a second polarization controller, and an optical fiber.

5. The optical frequency comb generating device based on Brillouin scattering and electro-optic modulator according to claim 4, characterized in that, The first and second lasers are narrow-linewidth semiconductor lasers.

6. The optical frequency comb generating device based on Brillouin scattering and electro-optic modulator according to claim 4, characterized in that, The first optical coupler is a 1×2 optical coupler, and the second optical coupler is a 2×2 optical coupler.

7. The optical frequency comb generating device based on Brillouin scattering and electro-optic modulator according to claim 4, characterized in that, The optical fiber is a fiber with a forward Brillouin scattering coefficient greater than 3 at 100MHz.

8. The optical frequency comb generating device based on Brillouin scattering and electro-optic modulator according to claim 4, characterized in that, The first electro-optic modulator and the second electro-optic modulator are cascaded to form a cascaded electro-optic modulator. The first electro-optic modulator is a Mach-Zehnder modulator, and the second electro-optic modulator is a dual parallel Mach-Zehnder modulator.

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