Noise suppression device for a multi-wavelength direct modulation laser

Abstract

The application discloses a noise suppression device of a multi-wavelength direct modulation laser, which comprises a direct modulation laser array, an optical splitter, a four-port fiber circulator, a low-loss nonlinear optical resonant cavity and a modulation module, the output of the direct modulation laser array is connected with the second port of the four-port fiber circulator, the third port of the four-port fiber circulator is connected with the low-loss nonlinear optical resonant cavity, the fourth port of the four-port fiber circulator is connected with the first port, and an injection locking closed loop is formed; the modulation module is electrically connected with the direct modulation laser array, the modulation frequency of the corresponding direct modulation laser is independently adjusted, and each wavelength laser can meet the resonance condition and the injection locking condition in the low-loss nonlinear optical resonant cavity, that is, the characteristic frequency shift is equal to the modulation frequency or an integer multiple of the modulation frequency. The application utilizes the super-narrow linewidth characteristic of nonlinear stimulated scattering and combines the injection locking technology, so that the linewidth of the direct modulation laser can be compressed to the Hz order, that is, the frequency noise is well suppressed. In addition, the application has the characteristics of multi-wavelength flexible adaptation, high cavity power utilization rate, simple structure and high integration degree.

Description

Technical Field

[0001] This invention belongs to the field of optical communication and lasers. More specifically, it relates to a noise suppression device for a directly modulated laser (DML), which is suitable for high-speed optical communication, microwave photonics and other scenarios with strict requirements for laser linewidth and noise level. Background Technology

[0002] Direct-modulated lasers are widely used in optical communication systems due to their simple structure, low cost, and fast response speed. However, due to their inherent operating mechanism, direct-modulated lasers suffer from problems such as high noise and wide linewidth in their output laser light. This noise severely degrades the signal-to-noise ratio of signal transmission, limiting communication distance and transmission rate.

[0003] Existing noise suppression techniques primarily target single-wavelength directly modulated lasers, typically employing external optical feedback or isolator combinations. However, these methods have significant drawbacks: first, they rely on specific narrow-linewidth light sources for feedback, leading to high system complexity; second, the need for additional isolators in the feedback path increases optical power loss and reduces energy efficiency; and third, in multi-wavelength scenarios, each laser requires an independent suppression module, resulting in poor compatibility and high costs. Furthermore, traditional cavity structure designs require isolators, leading to significant losses during pump light resonance, further limiting noise suppression effectiveness and output power stability.

[0004] To solve the noise suppression problem of multi-wavelength direct-modulated lasers, it is urgent to develop a noise suppression device that is simple in structure, low in loss, and can be flexibly adapted to multiple wavelengths. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a noise suppression device for multi-wavelength direct-modulation lasers, so as to be compatible with multi-wavelength application scenarios, meet the requirements of multi-channel optical communication and other scenarios for multi-wavelength laser synchronous noise reduction, and at the same time simplify the structure and improve power utilization.

[0006] To achieve the above-mentioned objective, the noise suppression device for a multi-wavelength directly modulated laser of the present invention is characterized by comprising:

[0007] A direct-modulation laser array, consisting of multiple direct-modulation lasers, is used to output lasers of multiple different wavelengths;

[0008] The fiber optic coupling unit, consisting of several fiber optic couplers, is used to couple lasers of different wavelengths from multiple directly modulated lasers together as the output of a laser array. The laser array output is divided into two paths: one path is used as noise suppression output, and the other path is used as forward pump light.

[0009] Low-loss nonlinear optical resonator, consisting of a single segment of optical fiber without additional circulators;

[0010] A four-port fiber optic circulator has a forward pump light input at port 2, a low-loss nonlinear optical resonator at port 3, and a feedback path formed by port 4 and port 1. The forward pump light, input at port 2, outputs from port 3 to the low-loss nonlinear optical resonator. Within the low-loss nonlinear optical resonator, under the excitation of the forward pump light, narrow-linewidth, backscattered light (i.e., backscattered light) is generated through nonlinear stimulated scattering. On one hand, the backscattered light returns to the fiber coupler through port 2 and is injected back into the direct-tuned laser array, forming an injection-locked loop. On the other hand, this backscattered light can serve as an ultra-narrow-linewidth continuous laser output, with a 10.6 + x GHz offset from the pump light, finely tuned by a factor of [missing value]. , ;

[0011] The modulation module, electrically connected to the directly modulated laser array, is used to independently apply intensity modulation to each directly modulated laser in the array. This ensures that the carrier wave dominates the output laser spectrum of each modulated laser, and that the power is equal. Furthermore, the distribution of the modulation sidebands in the output laser spectrum of each directly modulated laser matches its nonlinear stimulated scattering characteristic frequency shift; that is, the modulation frequency equals the characteristic frequency shift. Thus, the frequency of the backscattered light is equal to... The first-order modulation sidebands are used to satisfy the injection locking condition;

[0012] The backscattered light is fed back to the active region of the corresponding direct-modulated laser through a four-port fiber circulator and fiber coupling unit. The carrier of the direct-modulated laser is synchronously locked through the injection locking mechanism and the strict frequency spacing mechanism between the sideband and the carrier, thereby achieving linewidth compression and frequency noise suppression.

[0013] The objective of this invention is achieved as follows:

[0014] The noise suppression device for a multi-wavelength directly modulated laser of the present invention includes a directly modulated laser array, an optical fiber coupler, a four-port optical fiber circulator, a low-loss nonlinear optical resonator, and a modulation module. The output of the directly modulated laser array is connected to the second port of the four-port optical fiber circulator, the third port of the four-port optical fiber circulator is connected to the low-loss nonlinear optical resonator, and the fourth port of the four-port optical fiber circulator is connected to the first port, forming an injection-locked closed loop. The low-loss nonlinear optical resonator adopts an integrated structure without an additional circulator, ensuring that the pump light is retained in the cavity resonance to the maximum extent. The modulation module is electrically connected to the directly modulated laser array and is used to independently adjust the modulation frequency of the corresponding directly modulated laser according to the output wavelength of each directly modulated laser, so that the laser spectrum of each wavelength can satisfy the resonance condition and the injection-lock condition, i.e., the modulation frequency equals the characteristic frequency shift, within the low-loss nonlinear optical resonator.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. Significant noise suppression effect: By utilizing the ultra-narrow linewidth characteristics of nonlinear stimulated scattering and combining it with injection locking technology, the linewidth of the directly tuned laser can be compressed to the Hz level, thus achieving excellent noise suppression. The use of fiber optic coupling units and circulators ensures that there is no interference between multiple wavelengths during transmission, thereby guaranteeing the consistency of noise suppression effect.

[0017] 2. Flexible multi-wavelength adaptation: Multiple directly modulated lasers share the same low-loss cavity architecture. There is no need to configure independent suppression modules for different wavelengths. The injection locking condition of different directly modulated lasers can be controlled by adjusting the frequency of the modulation module, i.e., the characteristic frequency shift is equal to the modulation frequency or an integer multiple of the modulation frequency. This allows multiple directly modulated lasers to be locked to a single low-loss nonlinear optical resonator. The adapted wavelength range can cover the C-band.

[0018] 3. High cavity power utilization: The low-loss fiber nonlinear resonant cavity has no additional circulator structure and the cavity quality factor reaches the order of 10^8, which allows the multi-wavelength pump light to be retained in the cavity resonance to the greatest extent, reducing the pump power requirement of the laser, improving the power stability of the output laser, and ensuring the power advantage in the noise suppression process.

[0019] 4. Simple structure and high integration: The core functions of this invention can be achieved with only a direct-modulated laser, fiber coupler, four-port fiber circulator, low-loss nonlinear optical resonator and modulation module. It does not require complex optical modulation devices. The structure is simple and compact, easy to integrate and mass-produce, and reduces the manufacturing cost and debugging difficulty of the device. Attached Figure Description

[0020] Figure 1 This is a schematic diagram illustrating the principle of a specific embodiment of the noise suppression device for the multi-wavelength direct-modulation laser of the present invention;

[0021] Figure 2 This is a Q-value test diagram of a specific example of the low-loss nonlinear optical resonator used in this invention;

[0022] Figure 3 This is a spectral diagram of a key node on the laser transmission path in the noise suppression device of the multi-wavelength direct-tuned laser of the present invention;

[0023] Figure 4 This is a comparison chart of the frequency noise of the direct-modulated laser before and after injection locking. Detailed Implementation

[0024] The specific embodiments of the present invention will now be described with reference to the accompanying drawings to enable those skilled in the art to better understand the invention. It should be particularly noted that in the following description, detailed descriptions of known functions and designs that might obscure the main content of the invention will be omitted here.

[0025] This invention relates to a noise suppression device for multi-wavelength directly modulated lasers, aiming to address key defects and bottlenecks in existing technologies. Existing noise suppression techniques are mostly designed for single-wavelength directly modulated lasers, and their architectures are difficult to adapt to multi-wavelength applications, resulting in extremely poor adaptability and failing to meet the requirements for simultaneous noise reduction of multi-wavelength lasers in scenarios such as multi-channel optical communication. Furthermore, the optical cavities used in traditional technologies have significant inherent losses, leading to severe energy waste during pump light resonance within the cavity, significantly reducing utilization and requiring the input pump light to maintain high power. In addition, when adapting to multi-wavelength scenarios, existing technologies often require a separate noise suppression hardware module (including the optical cavity) for each laser wavelength, resulting in an extremely complex overall system structure, increased equipment integration difficulty and maintenance costs, and significantly higher overall application costs, thus limiting the promotion and application of this type of technology in large-scale multi-wavelength systems.

[0026] To address the aforementioned technical problems, this invention proposes a noise suppression device for multi-wavelength directly modulated lasers. Its core lies in constructing an injection-locking system comprising an optical fiber coupling unit, a four-port optical fiber circulator, a low-loss nonlinear optical resonator, and a modulation module. On one hand, leveraging the linewidth compression characteristic of nonlinear stimulated scattering light, the output noise of the directly modulated laser is effectively suppressed, improving the stability of the laser output. On the other hand, the optical fiber coupling unit couples the outputs of directly modulated lasers of different wavelengths together, forming a multi-wavelength laser array (MWLA). Through precise modulation frequency control, the frequency shift of the modulated laser outputs from different wavelengths is precisely matched with the nonlinear stimulated scattering characteristic of the corresponding low-loss nonlinear optical resonator. Furthermore, through the injection-locking mechanism and the strict frequency spacing between the sidebands and the carrier, the carrier of the directly modulated laser is synchronously locked, ultimately achieving multi-wavelength synchronous noise reduction. In addition, the nonlinear optical resonator used in this invention has the advantages of simple structure and high power utilization.

[0027] Figure 1 This is a schematic diagram illustrating the principle of a specific embodiment of the noise suppression device for the multi-wavelength direct-modulation laser of the present invention.

[0028] In this embodiment, as Figure 1As shown, the noise suppression device for the multi-wavelength directly modulated laser of the present invention includes: a directly modulated laser array 1 composed of multiple directly modulated lasers, an optical fiber coupling unit 2, a four-port optical fiber circulator 3, a low-loss nonlinear optical resonator 4, and a modulation module 5.

[0029] Multiple directly modulated lasers constitute a directly modulated laser array 1, used to output laser light of multiple different wavelengths. In this embodiment, for simplicity, the directly modulated laser array 1 includes two directly modulated lasers, namely directly modulated lasers 1 and 2. Directly modulated lasers 1 and 2 are coupled together through an optical fiber coupling unit 2 as the output of the directly modulated laser array, and are divided into two paths: one as a noise suppression output and the other as a forward pump light.

[0030] In this embodiment, the basic output wavelength of each directly modulated laser in the directly modulated laser array covers the C-band, i.e., 1530nm-1565nm. The wavelength spacing between adjacent directly modulated lasers can be adjusted within the range of 0.8nm-2nm, and each wavelength can be adapted to the resonance characteristics of the low-loss nonlinear optical resonator through the modulation module.

[0031] In specific implementation, the number of directly modulated lasers in the directly modulated laser array can be expanded to 2-8. Each directly modulated laser can independently adjust its modulation frequency through a modulation module, and all of them can be stably locked to the same low-loss nonlinear optical resonant cavity, realizing synchronous noise suppression output of 2-8 lasers with different wavelengths.

[0032] In this embodiment, the fiber optic coupling unit consists of multiple fiber optic couplers with an insertion loss of ≤0.6 dB. It is used to combine the different wavelength optical signals output by each directly modulated laser with low loss and input them into the circulator, while avoiding crosstalk between different wavelengths.

[0033] The low-loss nonlinear optical resonator 4 is composed of a single segment of optical fiber without an additional circulator.

[0034] The second port of the four-port fiber circulator 3 receives the forward pump light, the third port is connected to the low-loss nonlinear optical resonator 4, and the fourth port is connected to the first port to form a feedback path. In this way, the forward pump light is input from the second port and output from the third port to the low-loss nonlinear optical resonator 4. In the low-loss nonlinear optical resonator 4, under the excitation of the forward pump light, narrow-linewidth, reverse-propagating scattered light, i.e., backscattered light, is generated through the nonlinear stimulated scattering effect. The backscattered light returns to the fiber coupling unit 2 through the second port and is injected back into the direct-tuned laser array 1, forming an injection-locked closed loop.

[0035] The injection-locked closed loop uses narrow-linewidth reverse-transmission light excited in a low-loss nonlinear optical resonant cavity, which is then fed back into the directly modulated laser via a circulator to achieve injection locking of each directly modulated laser to suppress output noise. At the same time, through precise matching of modulation frequencies, multiple directly modulated lasers of different wavelengths are synchronously locked to the same low-loss nonlinear optical resonant cavity, achieving synchronous and stable output of multi-wavelength lasers.

[0036] Modulation module 5 is electrically connected to the directly modulated laser array 1, and is used to independently apply intensity modulation to each directly modulated laser in the directly modulated laser array 1, namely directly modulated laser 1 and 2, and generate their own intensity modulation. The system employs a +1 modulated sideband modulation mechanism to ensure that the carrier power in each set of laser spectra output from each directly modulated laser is equal. This allows the carrier in each set of modulated laser spectra to generate nonlinear stimulated scattering in a low-loss nonlinear optical resonator, resulting in a characteristic frequency shift. Furthermore, the frequency of the highest-power carrier in each modulated laser spectrum matches its nonlinear stimulated scattering characteristic frequency shift; that is, the modulation frequency equals the characteristic frequency shift. Consequently, the frequency of the backscattered light equals the +1 modulated sideband frequency, satisfying the injection-locking condition. The backscattered light is fed back to the active region of the corresponding directly modulated laser via a four-port fiber circulator and fiber coupling unit, synchronously locking the carrier of that directly modulated laser through the injection-locking mechanism, achieving linewidth compression and relative intensity noise suppression.

[0037] In this embodiment, the nonlinear stimulated scattering is stimulated Brillouin scattering, and its characteristic frequency shift... for:

[0038]

[0039] in, The refractive index of the optical fiber. The acoustic velocity in optical fiber. This corresponds to the output wavelength of the directly modulated laser;

[0040] The modulation module adjusts the modulation frequency of each direct-modulation laser. To make it meet the modulation frequency Feature frequency shift This is done to ensure that the frequency of the backscattered light is equal to the +1st order modulation sideband frequency, thereby satisfying the injection lock-in condition.

[0041] The working process of this invention is as follows:

[0042] (a) Apply intensity modulation with different modulation frequencies to each direct-modulated laser in the multi-wavelength direct-modulated laser array so that the output spectral carrier power of each direct-modulated laser is equal, thus becoming a high-power pump source;

[0043] (b) The pump light is input into a low-loss nonlinear optical resonator to excite nonlinear stimulated scattering corresponding to each wavelength in the cavity, thereby generating narrow-linewidth backscattered light;

[0044] (c) The backscattered light is fed back into the active region of the corresponding direct-tuned laser through a four-port fiber optic circulator;

[0045] (d) When the modulation frequency matches the nonlinear stimulated scattering characteristic frequency shift and the feedback light meets the injection locking condition, the carrier (i.e., pump light) is synchronously locked by locking the modulation sideband of this order with the feedback light, thereby completing the noise suppression.

[0046] Combination Figure 1 The detailed working process of this invention is as follows:

[0047] 1. Independent modulation of multi-wavelength directly modulated laser arrays

[0048] Modulation module 5 modulates the intensity of each directly modulated laser in the directly modulated laser array 1, generating a carrier frequency and multiple sidebands. This forms multiple sets of multi-wavelength transmission light, each centered on the wavelength of its own directly modulated laser and uniformly distributed at fixed intervals with its own modulation frequency. The frequencies are... , The modulation frequency is used to couple the components together through fiber optic coupling unit 2 as the output of the direct-modulated laser array 1.

[0049] By adjusting the modulation depth, the carrier wave is controlled to dominate the output spectrum of each group of lasers and has equal power, generally accounting for more than 90% of the total output optical power, thus becoming the core pump source for exciting nonlinear stimulated scattering.

[0050] Fiber optic coupling unit 2 splits the multiple laser beams of different wavelengths output from the directly modulated laser array 1 into two paths: one path serves as noise suppression output, and the other as forward pump light. Both paths are transmitted via single-mode fiber to port 2 of a four-port fiber optic circulator 3. After directional transmission within the four-port fiber optic circulator 3, the light is output from port 3 and enters the low-loss nonlinear optical resonant cavity 4. The four-port fiber optic circulator 3 possesses unidirectional transmission isolation characteristics, enabling directional transmission of optical signals.

[0051] 2. Parallel excitation of nonlinear stimulated scattering by multiple wavelengths within a single cavity

[0052] In each modulated output laser spectrum, the carrier power serves as the core pump light. Within the low-loss nonlinear optical resonator 4, due to the nonlinear stimulated scattering effect generated by acoustic phonons, it produces back-propagating scattered light, i.e., narrow-linewidth, low-noise backscattered light. The backscattered light exhibits a certain frequency shift compared to the forward pump light, i.e., a characteristic frequency shift. Characteristic frequency shift It corresponds strictly to the modulation frequency of a directly modulated laser, that is, the modulation frequency is equal to the characteristic frequency shift.

[0053] In this embodiment, the low-loss nonlinear optical resonator is a closed-loop fiber optic ring cavity, without any additional optical isolators or circulators. Due to the extremely low cavity loss, the cavity quality factor is very high. This is to maximize the resonant efficiency and energy utilization of each group of pump light within the cavity.

[0054] 3. Reverse nonlinear stimulated scattering injection locked direct-modulation laser

[0055] In this invention, when the intracavity optical power density reaches the nonlinear stimulated scattering threshold, narrow-linewidth backscattered light adapted to the three wavelengths is generated. The backscattered light is input through port 3 of the four-port fiber optic circulator 3, output from port 4, and then output through port 1 to port 2. It is then injected into the active region of the multi-wavelength directly modulated laser array by the fiber coupling unit, forming an injection-locked closed loop. Under the injection-locking effect, the output linewidth of each DML is compressed to the Hz level, achieving synchronous low-noise multi-wavelength output.

[0056] 4. Modulation sideband traction carrier synchronization locking and noise suppression

[0057] This invention employs an injection-locking mechanism: the backscattered light injected into the directly modulated laser has the same frequency as the modulation sideband, thus locking the directly modulated laser carrier. In this invention, the backscattered light is input through port 3 of the four-port fiber circulator 3, output from port 4, and then immediately output through port 1 to port 2, injected into the active region of the multi-wavelength directly modulated laser array. Since the modulation frequency is precisely aligned with the characteristic frequency shift of the corresponding directly modulated laser wavelength, the frequency of the backscattered light is close to the +1 order modulation sideband frequency. When the backscattered light power is ≥ 5% of the output power of the directly modulated laser and the frequency difference between the backscattered light and the target modulation sideband or carrier is within the injection-locking synchronization bandwidth of the directly modulated laser, that order modulation sideband is locked by the backscattered light; since the modulation sidebands are derived from the same carrier frequency oscillation, the frequency interval between each sideband and the carrier frequency is strictly equal to the modulation frequency (…). (If the frequency of the carrier wave is fixed, the locked sideband will pull the carrier wave frequency to shift synchronously, thereby achieving synchronous locking of the carrier wave (and pump light) and completing noise suppression.

[0058] Due to the linewidth compression effect of stimulated scattering, the linewidth of the backscattered light is much narrower than the inherent linewidth of the directly modulated laser, and its frequency is locked with the equivalent frequency modulated by the directly modulated laser, thereby synchronizing their respective carrier frequencies. In this embodiment, carrier synchronization locking is achieved by modulating the sideband to pull the carrier frequency synchronization offset, thus forcing the output laser frequency of the directly modulated laser to follow the narrow linewidth characteristics of the backscattered light, achieving injection locking, and compressing the laser linewidth to the order of hundreds of hertz. Finally, all connected directly modulated lasers obtain nonlinear stimulated scattering feedback through the same low-loss nonlinear optical resonator 4, simultaneously achieving linewidth compression and noise suppression.

[0059] 5. Multi-wavelength matching: Modulation module 5 provides an independent modulation channel for each directly modulated laser in the directly modulated laser array 1, thereby performing precise modulation to generate different sets of modulation sidebands. , (The modulation frequency). In this embodiment, the modulation frequency... For 10.6+x GHz, by fine-tuning the coefficients , Fine-tuning of the 10.6 GHz reference frequency was performed to accommodate directly modulated lasers of different wavelengths within the C-band, resulting in an actual modulation frequency range of 10.61-10.65 GHz. This was achieved based on the characteristic frequency shift formula for nonlinear stimulated scattering in standard single-mode fiber. , The refractive index of the optical fiber. The acoustic velocity within the optical fiber. To determine the output wavelength of the directly modulated laser, the wavelength of each directly modulated laser is independently adapted by a fine-tuning coefficient x, ensuring that the frequency of the modulated sideband is aligned with the center of the nonlinear stimulated scattering gain spectrum. The modulated multi-wavelength transmission lasers are simultaneously injected into the same low-loss nonlinear optical resonator 4. In each group of modulated light, the carrier wave acts as the core pump light, exciting a stable nonlinear stimulated scattering effect within the cavity, forming a narrow-linewidth backscattered light corresponding to its own wavelength. This backscattered light has a frequency close to the +1 first-order modulation sideband frequency of the directly modulated laser. It is injected into the directly modulated laser through a circulator and coupling unit to achieve locking, and the carrier wave is synchronously locked by strictly limiting the modulation interval. This "wavelength-modulation frequency" adaptation mechanism enables a single low-loss nonlinear optical resonator 4 to be compatible with locking multiple directly modulated lasers of different wavelengths. Its core advantage is that it eliminates the need to configure independent resonators, feedback modules, and filter modules for each wavelength. It achieves flexible matching between multi-wavelength locking and a single cavity simply by modulating electrical signals, ensuring that each directly modulated laser can obtain the best noise suppression effect without affecting the locking stability of other wavelengths. This greatly simplifies the structural complexity and cost of multi-wavelength systems.

[0060] Figure 3This is a spectral diagram of a key node on the laser transmission path in the noise suppression device of the multi-wavelength direct-tuned laser of the present invention.

[0061] In this embodiment, the modulation module 5 performs intensity modulation on the directly modulated lasers 1 and 2 in the directly modulated laser array 1, generating carrier frequencies and polarities respectively. Step edge zone as well as ,in, , These are the carrier frequencies, , These are the modulation frequencies, with the highest carrier frequency power serving as the pump light, also denoted as... as well as ,like Figure 3 As shown in S1.

[0062] Within the low-loss nonlinear optical resonator 4, the frequency is as well as The pump light, due to the nonlinear stimulated scattering effect generated by acoustic phonons, produces back-propagating scattered light with characteristic frequency shifts of [missing information]. , In this embodiment, the characteristic frequency shift is equal to the modulation frequency, i.e. , ,like Figure 3 As shown in S2.

[0063] Backscattered light injection locks onto a directly modulated laser, achieving modulation sideband traction carrier synchronization locking and noise suppression, such as... Figure 3 As shown in S3. Compared with the spectrum shown in S1, the linewidths of both the carrier frequency and the modulation sideband are significantly narrower, thus achieving carrier synchronization locking and noise suppression.

[0064] Figure 4 This is a comparison chart of the frequency noise of the directly modulated laser before and after injection locking.

[0065] In this embodiment, as Figure 4 As shown, the output noise of the directly modulated laser is significantly reduced before and after injection locking, down to the level of reflected and scattered light noise, achieving multi-wavelength laser synchronous noise reduction.

[0066] Although the illustrative specific embodiments of the present invention have been described above to enable those skilled in the art to understand the invention, it should be understood that the invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the invention as defined and determined by the appended claims, and all inventions utilizing the concept of the present invention are protected.

Claims

1. A noise suppression device for a multi-wavelength directly modulated laser, characterized in that, include: A direct-modulation laser array, consisting of multiple direct-modulation lasers, is used to output lasers of multiple different wavelengths; The fiber optic coupling unit, consisting of several fiber optic couplers, is used to couple lasers of different wavelengths from multiple directly modulated lasers together as the output of a laser array. The laser array output is divided into two paths: one path is used as noise suppression output, and the other path is used as forward pump light. Low-loss nonlinear optical resonator, consisting of a single segment of optical fiber without additional circulators; A four-port fiber optic circulator has a forward pump light input at port 2, a low-loss nonlinear optical resonator at port 3, and a feedback path formed by port 4 and port 1. The forward pump light, input at port 2, is output from port 3 to the low-loss nonlinear optical resonator. Within the low-loss nonlinear optical resonator, under the excitation of the forward pump light, narrow-linewidth, backscattered light (i.e., backscattered light) is generated through nonlinear stimulated scattering. This backscattered light returns to the fiber coupler at port 2 and is injected back into the direct-tuned laser array, forming an injection-locked loop. Simultaneously, it outputs as a narrow-linewidth continuous beam with a frequency offset of 10.6 + x GHz from the pump light. The fine-tuning coefficient... , ; The modulation module, electrically connected to the direct-modulated laser array, is used to independently apply intensity modulation to each direct-modulated laser in the array, so that the carrier dominates the laser spectrum of each direct-modulated laser after modulation and the power is equal, and the modulation sideband distribution of the laser spectrum of each direct-modulated laser after modulation matches its nonlinear stimulated scattering characteristic frequency shift, that is, the modulation frequency is equal to the characteristic frequency shift. In this way, the frequency of the backscattered light is equal to the +1 order modulation sideband frequency, thereby satisfying the injection lock condition. The backscattered light is fed back to the active region of the corresponding direct-modulated laser through a four-port fiber circulator and fiber coupling unit. Through the injection locking mechanism and the strict frequency interval limit between the modulation sideband and the carrier, the carrier is pulled to lock synchronously, thereby achieving linewidth compression and frequency noise suppression.

2. The noise suppression device for a multi-wavelength directly modulated laser according to claim 1, characterized in that, The nonlinear stimulated scattering is stimulated Brillouin scattering, with a characteristic frequency shift. for: ； in, The refractive index of the optical fiber. The acoustic velocity in optical fiber. This corresponds to the output wavelength of the directly modulated laser; The modulation module adjusts the modulation frequency of each direct-modulation laser. To make it meet the modulation frequency Feature frequency shift This is done to ensure that the frequency of the backscattered light is equal to the modulation sideband, thereby satisfying the injection lock condition.

3. The noise suppression device for a multi-wavelength directly modulated laser according to claim 1, characterized in that, The modulation frequency For 10.6+x GHz, by fine-tuning the coefficients , The 10.6 GHz reference frequency is finely adjusted to accommodate direct-modulation lasers of different wavelengths within the C-band, resulting in an actual modulation frequency range of 10.61-10.65 GHz.

4. The noise suppression device for a multi-wavelength directly modulated laser according to claim 1, characterized in that, The low-loss nonlinear optical resonant cavity is a closed-loop fiber optic ring cavity, without any additional optical isolators or circulators, and has a cavity quality factor of [missing information]. This is to maximize the resonant efficiency and energy utilization of the pump light within the cavity.

5. The noise suppression device for a multi-wavelength directly modulated laser according to claim 1, characterized in that, When the backscattered light power is greater than or equal to 5% of the output power of the directly modulated laser and the frequency difference between the backscattered light and the target modulation sideband is within the injection-locked synchronization bandwidth of the directly modulated laser, the modulation sideband of that order is locked by the backscattered light. By strictly limiting the modulation interval, the carrier frequency is pulled to lock synchronously, thereby compressing the laser linewidth to the Hertz level.

6. The noise suppression device for a multi-wavelength directly modulated laser according to claim 1, characterized in that, The modulation depth of the intensity modulation enables the carrier to obtain the highest power, accounting for 90% or more of the total output optical power, thus becoming the core pump source for exciting nonlinear stimulated scattering.

7. The noise suppression device for a multi-wavelength directly modulated laser according to claim 1, characterized in that, The injection-locking closed loop uses narrow-linewidth reverse-transmission light excited in a low-loss nonlinear optical resonant cavity, which is then fed back into the directly modulated laser via a circulator to achieve injection locking of each directly modulated laser to suppress output noise. At the same time, through precise matching of modulation frequencies, multiple directly modulated lasers of different wavelengths are synchronously locked to the same low-loss nonlinear optical resonant cavity, achieving synchronous and stable output of multi-wavelength lasers.

8. The noise suppression device for a multi-wavelength directly modulated laser according to claim 1, characterized in that, The basic output wavelength of each directly modulated laser in the array covers the C-band, i.e., 1530nm-1565nm. The wavelength spacing between adjacent directly modulated lasers can be adjusted within the range of 0.8nm-2nm, and each wavelength can be adapted to the resonance characteristics of the low-loss nonlinear optical resonator through the modulation module.

9. The apparatus according to claim 1, characterized in that, The fiber optic coupling unit consists of multiple fiber optic couplers with an insertion loss of ≤0.6 dB. It is used to combine the optical signals of different wavelengths output from each directly modulated laser with low loss and input them into the circulator, while avoiding crosstalk between different wavelengths.

10. The apparatus according to claim 1, characterized in that, The number of directly modulated lasers in the directly modulated laser array can be expanded to 2-8. Each directly modulated laser can independently adjust its modulation frequency through a modulation module, and all of them can be stably locked to the same low-loss nonlinear optical resonant cavity, realizing synchronous noise suppression output of 2-8 lasers with different wavelengths.

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