A Relaxation Oscillation Suppression Scheme for Fiber Bragg Grating Lasers

Abstract

The present invention provides a relaxation oscillation suppression scheme for a fiber grating laser, comprising: a splitter, a photodetector, a transimpedance amplifier, an amplifier, and a phase modulation circuit; the splitter is configured to allow a part of the output signal light to enter the photodetector, and the photodetector converts this part of the output signal light into a current signal; the current signal is then converted into a voltage signal by the transimpedance amplifier and amplified by the amplifier; the phase adjustment circuit performs phase adjustment on the amplified voltage signal to generate a relaxation oscillation suppression voltage signal, and the phase of the relaxation oscillation suppression voltage signal is 180° different from that of the relaxation oscillation signal; the relaxation oscillation suppression voltage signal is connected to a constant current source circuit for pump drive to suppress the relaxation oscillation signal. The above-mentioned relaxation oscillation optical path structure of the fiber grating laser is used to suppress the relaxation oscillation signal output by the grating and improve the RIN noise of the ultra-narrow linewidth laser.

Description

Technical Field

[0001] The present invention relates to a relaxation oscillation suppression scheme for a fiber grating laser. Background Art

[0002] Ultra-narrow linewidth lasers have relatively large applications in distributed fiber sensing, lidar, hydrophones, etc. Narrow linewidth fiber lasers have the advantages of a long gain region, compact structure, high energy density, strong anti-electromagnetic interference, small temperature expansion coefficient, and no need for additional heat dissipation. With the development of optical communication technology, the costs of fiber devices such as erbium-doped fibers, wavelength division multiplexers, and fiber gratings have decreased year by year, and the cost of fiber lasers has also decreased. Therefore, fiber lasers have become the mainstream lasers in the world today and have a tendency to replace solid-state lasers of the same wavelength.

[0003] Due to the broad application requirements of high-performance single-longitudinal-mode narrow linewidth fiber lasers in sensitive fields such as military, foreign countries have imposed embargoes on China in terms of core technologies and core materials, restricted the import of products, and it is of extremely important significance to research, develop, and build a production line of single-longitudinal-mode, narrow linewidth fiber lasers and equipment with independent intellectual property rights in China.

[0004] There are defects:

[0005] At present, the laser of the fiber grating has a RIN noise peak at the relaxation oscillation position. Therefore, if the customer needs information at this frequency point during use, it will cause strong interference signals in the signals measured within this frequency. Therefore, it is necessary to suppress the RIN noise of the relaxation oscillation signal. Summary of the Invention

[0006] The main technical problem to be solved by the present invention is to provide a relaxation oscillation suppression scheme for a fiber grating laser, which is used to suppress the relaxation oscillation signal output by the grating and improve the RIN noise of the ultra-narrow linewidth laser.

[0007] To solve the above technical problems, the present invention provides a relaxation oscillation suppression scheme for a fiber grating laser, including: a splitter, a photodetector, a transimpedance amplifier, an amplifier, and a phase modulation circuit;

[0008] The splitter is used to allow a part of the output signal light to enter the photodetector, and the photodetector converts this part of the output signal light into a current signal; the current signal is then converted into a voltage signal by the transimpedance amplifier and then amplified by the amplifier; the phase adjustment circuit adjusts the phase of the amplified voltage signal to generate a relaxation oscillation suppression voltage signal, and the phase of the relaxation oscillation suppression voltage signal is 180° different from that of the relaxation oscillation signal; the relaxation oscillation suppression voltage signal is connected to the constant current source circuit for pumping drive to suppress the relaxation oscillation signal.

[0009] In a preferred embodiment, the cathode of the photodetector is connected to the output end of the optical splitter, and the anode is connected to the negative input end of the transimpedance amplifier.

[0010] In a preferred embodiment, the positive input end of the transimpedance amplifier is grounded, and a resistor is connected between the negative terminal and the output terminal of the transimpedance amplifier, and the resistor is in parallel with a capacitor.

[0011] In a preferred embodiment, the phase modulation circuit includes a 90° - 180° phase shift circuit and a 180° - 270° phase shift circuit.

[0012] In a preferred embodiment, a non-inverting adder is further included. The relaxation oscillation suppression voltage signal is input to the "LD_AC_BACK" terminal of the non-inverting adder and superimposed on the DC signal "LD_DC_SET" output by the single-chip microcomputer DAC, so as to enable the laser to generate a current signal with a reverse phase, and further generate a signal with a reverse phase to the relaxation oscillation signal on the light to suppress the relaxation oscillation signal.

[0013] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0014] 1. The present invention provides a relaxation oscillation suppression scheme for a fiber grating laser. By using a high-speed operational amplifier for TIA circuit design, the relaxation oscillation signal can be completely restored.

[0015] 2. The present invention provides a relaxation oscillation suppression scheme for a fiber grating laser. By using a specially designed phase shift circuit, a phase shift of 90 degrees to 270 degrees can be performed, and a digital potentiometer is added, and the phase can be adjusted by software.

[0016] 3. The present invention provides a relaxation oscillation suppression scheme for a fiber grating laser. The overall relaxation oscillation signal can achieve a suppression effect of about 25 dB.

[0017] 4. The present invention provides a relaxation oscillation suppression scheme for a fiber grating laser, with low cost and no need to add suppression devices for the optical path scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the optical path structure diagram of the relaxation oscillation of the fiber grating laser in the preferred embodiment of the present invention;

[0019] Figure 2 It is the circuit diagram of the transimpedance amplifier in the preferred embodiment of the present invention;

[0020] Figure 3 It is the circuit diagram of the 90° - 180° phase shift circuit in the preferred embodiment of the present invention;

[0021] Figure 4 This is the circuit diagram of the 180°-270° phase shift in the preferred embodiment of the present invention;

[0022] Figure 5 This is the circuit diagram of the current source in the preferred embodiment of the present invention. Detailed implementation manners

[0023] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "outer", "top / bottom end", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0025] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "provided with", "sheathed / connected", "connected", etc. should be understood in a broad sense. For example, "connected" can be a wall-mounted connection, a detachable connection, or an integral connection, it can be a mechanical connection, an electrical connection, a direct connection, or an indirect connection through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0026] Referring to Figures 1 - 5 , the present invention provides a relaxation oscillation suppression scheme for a fiber grating laser, including: a splitter, a photodetector, a transimpedance amplifier, an amplifier, and a phase modulation circuit;

[0027] The splitter is used to allow a part of the output signal light to enter the photodetector, and the photodetector converts this part of the output signal light into a current signal; the current signal is then converted into a voltage signal through a transimpedance amplifier and then amplified by an amplifier; the phase adjustment circuit adjusts the phase of the amplified voltage signal to generate a relaxation oscillation suppression voltage signal, and the phase of the relaxation oscillation suppression voltage signal is 180° different from the relaxation oscillation signal; the relaxation oscillation suppression voltage signal is connected to the constant current source circuit for pump drive to suppress the relaxation oscillation signal.

[0028] In this embodiment, the overall bandwidth of the circuit needs to be considered during the design. Since the signal frequency of the relaxation oscillation signal is around approximately 250 KHz, an operational amplifier with a relatively high bandwidth and a small Ibias needs to be considered for the transimpedance amplifier. At the same time, an anti-bias connection method is adopted to increase the signal rate.

[0029] Specifically, the cathode of the photodetector is connected to the output end of the optical splitter, and the anode is connected to the negative input terminal of the transimpedance amplifier. The positive input terminal of the transimpedance amplifier is grounded, and a resistor is connected between the negative terminal and the output terminal of the transimpedance amplifier, and the resistor is in parallel with a capacitor.

[0030] Because the overall phase shift is around approximately 180 degrees, a circuit with a phase shift of 90 degrees to 270 degrees needs to be reserved. Therefore, the phase modulation circuit includes a 90° - 180° phase shifter circuit and a 180° - 270° phase shifter circuit. For the specific circuit diagram, please refer to Figure 3 and Figure 4 。

[0031] In this embodiment, a non-inverting adder is further included. The relaxation oscillation suppression voltage signal is input to the "LD_AC_BACK" terminal of the non-inverting adder and is superimposed with the DC signal "LD_DC_SET" output by the single-chip microcomputer DAC, so as to enable the laser to generate a current signal with a reverse phase, and further generate a signal with a reverse phase to the relaxation oscillation signal on the light to suppress the relaxation oscillation signal.

[0032] As described above, the above is only the preferred specific embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention who makes non-substantive modifications to the present invention using this concept shall fall within the scope of infringement of the protection of the present invention.

Claims

1. A relaxation oscillation suppression structure for a fiber grating laser, characterized in that Comprising: An optical splitter, a photodetector, a transimpedance amplifier, an amplifier, and a phase modulation circuit; The optical splitter is configured to allow a part of the output signal light output from the fiber grating laser to enter the photodetector, and the photodetector converts this part of the output signal light into a current signal; the current signal is then converted into a voltage signal by the transimpedance amplifier and then amplified by the amplifier; the phase modulation circuit performs phase modulation on the amplified voltage signal to generate a relaxation oscillation suppression voltage signal, and the phase of the relaxation oscillation suppression voltage signal is 180° different from the relaxation oscillation signal in the fiber grating laser; the relaxation oscillation suppression voltage signal is connected to the constant current source circuit for pumping drive in the fiber grating laser to suppress the relaxation oscillation signal; The cathode of the photodetector is connected to the output end of the optical splitter, and the anode is connected to the negative input end of the transimpedance amplifier; The positive input end of the transimpedance amplifier is grounded, and a resistor is connected between the negative terminal and the output terminal of the transimpedance amplifier, and the resistor is connected in parallel with a capacitor; The phase modulation circuit includes a 90°-180° phase shifter and a 180°-270° phase shifter; It further includes a non-inverting adder. The relaxation oscillation suppression voltage signal is input to the "LD_AC_BACK" terminal of the non-inverting adder and superimposed with the DC signal "LD_DC_SET" output by the single-chip microcomputer DAC, so as to enable the constant current source circuit to generate a current signal with a reverse phase, and further generate a signal with a reverse phase to the relaxation oscillation signal on the light to suppress the relaxation oscillation signal.

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