CN104979747B - Integrated reflective phase bias device and optical fiber laser and light wave microwave phase discriminator - Google Patents

Abstract

The invention discloses an integrated reflective phase offset device, a fiber laser and a light wave-microwave phase detector. The phase bias device of the present invention includes a fiber holder, a collimating lens, a polarizing prism, a Faraday rotator, a birefringent crystal and a reflector; Optical fiber and polarizing prism separate two paths of light whose polarization directions are perpendicular to each other, only need a collimator, a Faraday rotator, a birefringent crystal, a mirror, small size, high stability, low price, no need for any adjustment ;For fiber lasers, self-starting mode-locked pulse trains can be obtained, and the characteristics of the pulse trains are not disturbed by the external environment, and can be applied to various complex environments such as high noise, heavy pollution or emission; used for lightwave-microwave identification The phase device can make it more miniaturized, free from external interference, and work more reliably.

Description

Integrated Reflective Phase Biaser, Fiber Laser and Lightwave-Microwave Phase Detector

technical field

The invention relates to fiber laser technology, in particular to an integrated reflective phase offset device, a fiber laser and a light wave-microwave phase detector.

Background technique

Mode-locked fiber lasers have ultra-short pulses, definite repetition rates, and high peak power, and have irreplaceable application values in scientific research and industrial processing. However, compared with ordinary lasers, mode-locked lasers are difficult to self-start, susceptible to external interference, and high in price, which hinders their application.

There are three main modes-locking schemes in fiber lasers: nonlinear loop mirrors, saturable absorbers, and nonlinear polarization rotation. The 8-shaped mode-locked fiber laser composed of nonlinear loop mirrors is difficult to start in mode-locking, and often requires external push instead of polarization-maintaining fiber; the semiconductor saturable absorber in the saturable absorber has a long life and is easy to damage; other carbon-based Saturable absorbers, such as carbon nanotubes, graphene, etc., are easily degraded and lose the mode-locking start-up function in the natural environment. Nonlinear polarization rotation can provide a stable and reliable mode-locked initiation mechanism, delivering very high average power, and can utilize almost all pulse forming mechanisms to obtain high or low repetition rate, picosecond or femtosecond pulse trains. However, the nature of its use of nonlinear polarization rotation determines that it must use a non-polarization-maintaining fiber, and the non-polarization-maintaining fiber determines that this laser must be sensitive to the environment.

The nonlinear loop mirror was the earliest mode-locking device, and the double-loop fiber laser (figure-eight fiber laser) made of it can provide mode-locked pulses. But it is basically not self-starting. The reason is that its loop is zero biased. At zero bias, however, the loop mirror is less sensitive to nonlinear phase shifts. Therefore a phase offset is required. The so-called phase offset means that the light propagating relatively in the same optical path experiences different phase shifts.

The optical wave-microwave phase detector in the paper "Subfemtosecondsynchronization of microwave oscillators with mode-locked Er-fiber lasers" published by Jungwon Kim (Jin Zhengyuan) and others on Optics Letters uses an asymmetric phase shifter and uses it as an optical fiber The phase shifter in the ring, but it is composed of discrete spatial elements, and it is transmissive, not reflective, requiring two Faraday rotators, and there is no polarizing prism in the phase shifter.

Menlo Systems' patent application "Laser with non-linear optical loopmirror". (US201500711322) utilized the phase shifter and phase bias method of Jungwon Kim et al. to form a mode-locked laser. The phase shifter is also transparent, requiring two Faraday rotators, and there is no polarizing prism in the phase shifter

"A mode-locked thulium-doped fiber laser based on a nonlinear loop mirror" paper published by Honzatko et al. on Optics Letters in 2013, and "Direct generation of 2W average" published by Huang et al. on Optics Letters in 2015 -power and 232nJpicosecond pulses from an ultra-simple Yb-doped double-clad fiber laser" paper, there is no phase bias device, so very high pulse power is required to reach the mode-locking threshold, and the pulse is very wide (hundreds of picoseconds to a few nanoseconds).

Contents of the invention

In order to obtain self-starting and long-term stable mode-locking in fiber lasers, and overcome the mode-locking degradation caused by changes in environmental parameters such as temperature and vibration, the present invention proposes an integrated reflective phase biaser and its fiber laser and light wave -Microwave phase detector.

The object of the present invention is to provide an integrated reflective phase biaser, its fiber laser and light wave-microwave phase detector.

The integrated reflective phase biaser of the present invention includes: a fiber holder, a collimating lens, a polarizing prism, a Faraday rotator, a birefringent crystal, and a mirror; wherein, the fiber holder fixes the first and second polarization-maintaining optical fiber, the fast axes and slow axes of the two polarization-maintaining fibers are perpendicular to each other, and they are input and output to each other; after passing through the first polarization-maintaining fiber, the incident light whose polarization direction is along one axis of the first polarization-maintaining fiber passes through After the collimator lens is collimated, it enters the Faraday rotator through the polarizing prism at an angle; the Faraday rotator rotates the polarization direction of the incident light by 45 degrees so that the polarization direction is parallel to one axis of the birefringent crystal; and then enters the birefringent crystal , after a phase shift of φ ₁ /2, it is vertically incident on the reflector; after being reflected by the reflector, it returns, and the phase shift is doubled to φ ₁ through the birefringent crystal again; after passing through the Faraday rotator again, the polarization direction is rotated by 45 degrees, and The polarization direction of the incident light coming out of the first polarization-maintaining fiber before entering the polarizing prism is vertical; after passing through the polarizing prism, since the polarization directions of the return light and the incident light are perpendicular to each other, the angle after exiting the polarizing prism is different from the angle of the incident light, thus After exiting from the polarizing prism at another angle, it enters the second polarization-maintaining fiber through the collimating lens, and the polarization direction is along the same axis of the second polarization-maintaining fiber, thereby exiting from the second polarization-maintaining fiber; in the same way, The incident light passing through the second polarization-maintaining fiber, the polarization direction is along one axis of the second polarization-maintaining fiber, after being rotated by the Faraday rotator, the polarization direction is parallel to the other axis of the birefringent crystal, and goes back and forth along the opposite path Afterwards, a phase shift of φ ₂ occurs, and the polarization direction enters the first polarization-maintaining fiber along the same axis of the first polarization-maintaining fiber, and exits from the first polarization-maintaining fiber, where φ ₁ ≠φ ₂ .

The polarization-maintaining fiber has two axes, a fast axis and a slow axis. The polarization-maintaining directions of the two polarization-maintaining fibers are perpendicular to each other in space, that is, the fast axes of the two polarization-maintaining fibers are perpendicular to each other, and the slow axes of the two fibers are perpendicular to each other. The polarization directions of the incident light passing through the first and second polarization-maintaining fibers are perpendicular to each other in space before entering the polarizing prism, so as to ensure that the polarization direction of the incident light from a polarization-maintaining fiber is along the fast axis, and round-trip the polarization direction After rotating 90 degrees, the polarization direction of the returning light entering the other polarization maintaining fiber is still along the fast axis of the other fiber. Similarly, the polarization direction of the incident light of one polarization maintaining fiber is along the slow axis, and the returning light enters the other One PM fiber remains along the slow axis of the other fiber.

Take the polarization direction along the slow axis as an example: the polarization direction of the incident light passing through the first polarization-maintaining fiber is along the slow axis, passes through the collimator lens, passes through the polarization prism at an angle, and then enters the Faraday rotation mirror, and its polarization direction is rotated by 45 degree, parallel to the slow axis (or fast axis) of the birefringent crystal, after obtaining the phase shift φ _1/2 , it is incident on the reflector; it returns after being reflected by the reflector, and doubles as φ ₁ through the phase shift of the birefringent crystal again; After passing through the Faraday rotator again, the polarization direction is rotated by 45 degrees, which is perpendicular to the polarization direction of the incident light. Since the polarization directions of the return light and the incident light are perpendicular to each other, the angle after exiting the polarizing prism is different from the angle of the incident light, thus entering Into the second polarization-maintaining fiber, since the slow axis of the second polarization-maintaining fiber and the first polarization-maintaining fiber are perpendicular to each other, the polarization direction is still along the slow axis of the second polarization-maintaining fiber, thereby exiting from the second polarization-maintaining fiber. In the same way, the polarization direction of the incident light passing through the second polarization-maintaining fiber is along the slow axis, passes through the collimator lens, enters the polarizing prism at another angle, and then enters the Faraday rotator, and its polarization direction is rotated by 45 degrees, which is the same as The fast axis (or slow axis) of the birefringent crystal is parallel, and after obtaining the phase shift φ ₂ /2, it is incident on the mirror; after being reflected by the mirror, it returns, and the phase shift of the birefringent crystal is doubled to φ ₂ again; After the rotator, the polarization direction is rotated by another 45 degrees, which is perpendicular to the polarization direction of the incident light from the second polarization-maintaining fiber. Since the polarization directions of the return light and the incident light are perpendicular to each other, the angle after exiting the polarizing prism is the same as that of the incident light. The angles are different, thus entering the first polarization-maintaining fiber, since the slow axes of the first polarization-maintaining fiber and the second polarization-maintaining fiber are perpendicular to each other, the polarization direction is still along the slow axis of the first polarization-maintaining fiber, thus from the first polarization-maintaining fiber Output from polarization maintaining fiber.

The polarization maintaining fiber adopts one of large mode area polarization maintaining fiber, doped gain polarization maintaining fiber, large mode area double cladding polarization maintaining fiber and polarization maintaining photonic crystal fiber. Polarization-maintaining fiber is doped so that it has gain characteristics. Select or design the polarization maintaining fiber according to the wavelength, not limited by the wavelength. The end of the polarization maintaining fiber is treated with angle or mode field area. The polarization-maintaining directions of the two polarization-maintaining fibers are perpendicular to each other in space.

A birefringent crystal includes two axes, a fast axis and a slow axis. The Faraday rotator rotates the polarization direction of the incident light by an angle, so that the polarization direction is rotated to be parallel to one axis of the birefringent crystal; while the incident light from another polarization-maintaining fiber passes through the same Faraday rotator, its polarization direction is rotated to be parallel to the other axis of the birefringent crystal. The Faraday rotator adopts a sheet-type Faraday rotator, or a Faraday rotator formed by inserting a magneto-optical crystal into a permanent magnet.

The fast axis and slow axis of the birefringent crystal in the phase biaser of the present invention introduce an asymmetric phase shift, resulting in a difference in phase shift of light propagating with polarizations parallel to different axes, ie phase offset. Incidence from the first polarization-maintaining fiber, exit from the second polarization-maintaining fiber for a round trip, a phase shift of φ ₁ occurs, incident from the second polarization-maintaining fiber, exit from the first polarization-maintaining fiber for a round trip, and a phase shift of ₂ , the phase shift difference between the two The size of is determined by the nature and thickness of the birefringent crystal, that is, Among them, n _e is the refractive index of light e, n _o is the refractive index of light o, l is the thickness of the birefringent crystal, and λ is the wavelength. A birefringent crystal, or a system or a combination of birefringent crystals of different thicknesses is used to form a specific phase difference and provide arbitrarily set phase offset.

Further, the present invention also includes an encapsulating steel pipe, wherein the fiber holder, collimating lens, polarizing prism, Faraday rotator, birefringent crystal and reflector are sequentially installed in the encapsulating steel pipe.

Fiber holders are shaped quartz glass tubes that are compatible with polarization-maintaining fibers. The polarizing prism is a Wollaston prism.

The collimating lens collimates the light output from the fiber, using a graded index fiber or an aspheric lens.

The integrated reflective phase biaser of the invention can be used in fiber lasers and light-wave-microwave phase detectors.

The fiber laser of the present invention comprises: a fiber beam splitter, a wavelength division multiplexer and a phase biaser; wherein the fiber beam splitter includes first to fourth ports; the mode-locked laser pulse is input to the first port of the fiber beam splitter port, the evanescent wave in the polarization-maintaining fiber connected to the first and second ports is coupled into the polarization-maintaining fiber connected to the third and fourth ports, so as to output from the second and third ports; the lock output from the second port The mode-locked laser pulse is input to a polarization-maintaining fiber of the phase biaser through the wavelength division multiplexer and the gain fiber; the mode-locked laser pulse output from the third port is input to the other polarization-maintaining fiber of the phase biaser; The mode-locked laser pulse returned by the biaser passes through the third port of the fiber splitter, and is output from the first port and the fourth port of the fiber splitter.

The optical fiber beam splitter is a 2×2 beam splitter. Through the 2×2 beam splitter, the incident light is divided into two oppositely propagating lights, and an asymmetric phase difference is obtained in the phase biaser, and then returned to the beam splitter. A fiber optic loop is formed; light propagating in opposite directions interferes at the beam splitter, resulting in changes in the intensity of the output light at the other two ends of the beam splitter. The difference from ordinary nonlinear fiber loop mirrors is that the phase biaser can preset the intensity ratio of the output light at the two output ends of the beam splitter, as well as the direction and slope of the intensity change.

The fiber laser of the present invention can obtain a self-starting mode-locked laser pulse train, and the characteristics of the pulse train are not disturbed by the external environment; all pulse forming mechanisms that can be used in nonlinear polarization rotation mode-locked fiber lasers can be used, including soliton , self-similarity, total positive dispersion, and amplified self-similarity. The output port of the fiber laser can be set as the fourth port of the fiber beam splitter, or it can be set at the first port by using a partial reflector, or through a fiber coupling beam splitter. The first port can also be attached with a fiber mirror, or a spatial dispersion compensation device and a mirror, or a filter; the spatial dispersion compensation device is such as a pair of prisms, a pair of gratings, a pair of chirped mirrors, and the like. Fiber splitters can be integrated with mirrors and wavelength division multiplexers to form a single device. Fiber lasers will introduce nonlinear effects, which produce nonlinear phase shifts; this phase shift is combined with phase bias to form a discrimination mechanism for pulsed light and continuous light. Depending on the positive or negative bias, the first and fourth ports of the fiber splitter output will generate a reflection bias for high power pulses, or a transmission bias, which can be used as an initiation mechanism for mode-locked pulses.

The optical-microwave phase detector of the present invention includes: a balanced photodetector, a circulator, an optical fiber splitter, a wavelength division multiplexer and a phase biaser; wherein, the optical fiber splitter includes first to fourth ports; The mode-locked laser pulse enters the first port of the fiber beam splitter through the circulator, and the evanescent wave in the polarization-maintaining fiber connected to the first and second ports is coupled into the polarization-maintaining fiber connected to the third and fourth ports, thereby from Output from the second and third ports; the mode-locked laser pulse output from the second port is input to a polarization-maintaining fiber connected to the phase biaser after passing through the wavelength division multiplexer; the mode-locked laser pulse output from the third port is input Another polarization-maintaining fiber to the phase biaser; the mode-locked laser pulses returned from the phase biaser are input to the fiber beam splitter through the second port and the third port respectively, and the locked laser pulses output from the first port are respectively The mode-locked laser pulse enters one input port of the balanced photodetector after passing through the circulator, and the mode-locked laser pulse output from the fourth port enters the other input port of the balanced photodetector, and outputs from the output port of the balanced photodetector DC level.

The DC level of the output port obtains a linear output near the balance point in the balanced detector, and this linear output is proportional to the frequency difference of the optical-electrical signal. This linear relationship can be used to lock the optical frequency to the RF frequency attached to the modulator.

Advantages of the present invention:

In the present invention, two polarization-maintaining optical fibers whose polarization-maintaining directions are perpendicular to each other are fixed in a fiber holder, and a polarizing prism separates two paths of light whose polarization directions are perpendicular to each other. Only a collimator, a Faraday rotator, and a birefringent crystal are needed. , a reflector, small in size, high in stability, low in price, and does not require any adjustments; used in fiber lasers, a self-starting mode-locked pulse train can be obtained, and the characteristics of the pulse train are not disturbed by the external environment, and can be applied to Various complex environments such as high noise, heavy pollution or emission; used in light-wave-microwave phase detectors can make it more miniaturized, free from external interference, and work more reliably.

Description of drawings

1 is a schematic diagram of an integrated reflective phase biaser of the present invention;

Fig. 2 is the schematic diagram that the integrated reflective phase biaser of the present invention is used in fiber laser;

FIG. 3 is a schematic diagram of an integrated reflective phase offset device of the present invention used in a lightwave-microwave phase detector.

detailed description

The present invention will be further described through the embodiments below in conjunction with the accompanying drawings.

As shown in Figure 1, the integrated reflective phase biaser of this embodiment includes: fiber holder 1, collimator lens 2, polarizing prism 3, Faraday rotator 4, birefringent crystal 5, mirror 6, package Steel pipe 7 and two polarization-maintaining optical fibers 8 and 8'; fiber holder 1 fixes first and second polarization-maintaining optical fibers 8 and 8', the fast axes and slow axes of these two polarization-maintaining optical fibers are perpendicular to each other, and are input and output each other; the incident light passing through the first polarization-maintaining optical fiber 8 has a polarization direction along the slow axis, and after being collimated by the collimating lens 2, it enters the Faraday rotator 4 through the polarizing prism 3 at an angle; the Faraday rotator 4 will The polarization direction of the incident light is rotated by 45 degrees, so that the polarization direction is parallel to the fast axis of the birefringent crystal 5; then it is incident on the birefringent crystal 5, a phase shift occurs by φ ₁ /2, and it is vertically incident on the reflector 6; through the reflector 6 After reflection, the original path returns, and the returned light passes through the birefringent crystal 5 and doubles the phase shift to φ ₁ again; after passing through the Faraday rotator 4, the polarization direction is rotated by 45 degrees, and is perpendicular to the polarization direction of the incident light; after passing through the polarizing prism 3, due to The polarization directions of the return light and the incident light are perpendicular to each other, and the angle after exiting the polarizing prism 3 is different from that of the incident light, so that it enters the second polarization-maintaining fiber 8', and the polarization direction is still along the second polarization-maintaining fiber The slow axis of 8' emerges from the second polarization-maintaining optical fiber 8'.

The incident light passing through the second polarization-maintaining fiber 8' has a polarization direction along the slow axis of the second polarization-maintaining fiber 8', and is incident to the Faraday rotator 4 through the polarizing prism 3 at another angle; the Faraday rotator 4 converts the polarization of the incident light The direction is rotated by 45 degrees so that the polarization direction is parallel to the slow axis of the birefringent crystal 5; Out, the phase shift is φ ₂ , where φ ₁ ≠φ ₂ . phase shift difference The size of is determined by the nature and thickness of the birefringent crystal, that is,

As shown in Figure 2, the fiber laser includes: a fiber splitter 12, a wavelength division multiplexer 15, a phase biaser 11, and an element 18; wherein, the fiber splitter 12 includes first to fourth ports ① to ④; The mode-locked laser pulse is input to the first port ① of the fiber beam splitter, and the evanescent wave in the polarization-maintaining fiber connected to the first port ① and the second port ② is coupled into the polarization-maintaining fiber connected to the third port ③ and the fourth port ④. In the optical fiber, thus output from the second and third ports; the mode-locked laser pulse output from the second port is input to a polarization-maintaining optical fiber of the phase biaser 11 through the wavelength division multiplexer 15; the output from the third port The mode-locked laser pulse is input to another polarization-maintaining fiber of the phase biaser; the mode-locked laser pulse returned from the phase biaser passes through the third port of the fiber splitter, and passes through the first and fourth Port ① and ④ output. Element 18 may be a fiber optic mirror, or a spatial dispersion compensating device and mirror, or a filter.

As shown in Figure 3, the light-wave-microwave phase detector includes: balanced photodetector 14, circulator 13, optical fiber beam splitter 12, wavelength division multiplexer 15 and phase bias device 11; Wherein, optical fiber beam splitter 12 includes the first to fourth ports ①～④; the mode-locked laser pulse 16 enters the first port ① of the fiber beam splitter through the circulator 13, and the evanescent wave in the polarization-maintaining fiber connected to the first and second ports is coupled into The polarization-maintaining fiber connected to the third and fourth ports, so as to be output from the second and third ports; the mode-locked laser pulse output from the second port is input to one connected to the phase biaser after passing through the wavelength division multiplexer Polarization-maintaining fiber; the mode-locked laser pulse output from the third port is input to another polarization-maintaining fiber of the phase biaser; the mode-locked laser pulse returned from the phase biaser 11 passes through the second port and the third port respectively port input to the fiber beam splitter 12, the mode-locked laser pulse output from the first port respectively enters an input port of the balanced photodetector 14 after passing through the circulator 13, and the mode-locked laser pulse output from the fourth port enters the balanced photodetector 14 The other input port of the photodetector 14 outputs a DC level from the output port 17 of the balanced photodetector.

Finally, it should be noted that the purpose of publishing the implementation is to help further understand the present invention, but those skilled in the art can understand that various replacements and modifications can be made without departing from the spirit and scope of the present invention and the appended claims. It is possible. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the protection scope of the present invention is subject to the scope defined in the claims.

Claims (10)

1. An integrated reflective phase offset device, characterized in that, the phase offset device includes: an optical fiber holder, a collimating lens, a polarizing prism, a Faraday rotator, a birefringent crystal and a mirror; wherein, The fiber holder fixes the first and second polarization-maintaining fibers. The fast axes of the two polarization-maintaining fibers are perpendicular to each other, and the slow axes are perpendicular to each other, and are input and output to each other; after passing through the first polarization-maintaining fiber, the polarization direction The incident light along one axis of the first polarization-maintaining optical fiber is collimated by the collimating lens, and enters the Faraday rotator through the polarizing prism at an angle; the Faraday rotator rotates the polarization direction of the incident light by 45 degrees to make the polarization The direction is parallel to one axis of the birefringent crystal; then it is incident on the birefringent crystal, and after a phase shift of φ ₁ /2, it is vertically incident on the mirror; it returns after being reflected by the mirror, and the phase shift of the birefringent crystal is doubled to φ again ₁ ; after passing through the Faraday rotator again, the polarization direction is rotated by 45 degrees, which is perpendicular to the polarization direction of the incident light coming out of the first polarization-maintaining fiber before entering the polarizing prism; after passing through the polarizing prism, since the polarization directions of the returning light and the incident light are perpendicular to each other , the angle after exiting from the polarizing prism is different from the angle of the incident light, so that it exits from the polarizing prism at another angle and enters the second polarization-maintaining fiber through the collimating lens, and the polarization direction is along the same direction of the second polarization-maintaining fiber One axis, so as to emerge from the second polarization maintaining fiber; in the same way, the incident light passing through the second polarization maintaining fiber, the polarization direction is along one axis of the second polarization maintaining fiber, and after going back and forth along the opposite path, after After the Faraday rotator rotates, the polarization direction is parallel to the other axis of the birefringent crystal, and the phase shift is φ ₂ , and the polarization direction enters the first polarization-maintaining fiber along the same axis of the first polarization-maintaining fiber, so that The polarized fiber exits, where φ ₁ ≠φ ₂ . 2. The phase biaser according to claim 1, wherein the Faraday rotator rotates the polarization direction of the incident light by 45 degrees, so that the polarization direction is rotated to be parallel to one axis of the birefringent crystal; The incident light of a polarization-maintaining fiber passes through the same Faraday rotator, and its polarization direction is rotated to be parallel to the other axis of the birefringent crystal. 3. The phase offset device according to claim 2, wherein the fast axis and the slow axis of the birefringent crystal introduce an asymmetric phase shift, resulting in a phase shift difference of light propagating with polarizations parallel to different axes , that is, the phase offset, incident from the first polarization-maintaining fiber, exiting from the second polarization-maintaining fiber for a round trip, with a phase shift of φ ₁ , incident from the second polarization-maintaining fiber, exiting from the first polarization-maintaining fiber for a round-trip , the phase shift is φ ₂ , the phase shift difference between the two The size of is determined by the nature and thickness of the birefringent crystal, that is, Among them, n _e is the refractive index of light e, no is the refractive index of light o, l is the thickness of the birefringent crystal, and λ is the wavelength. 4. The phase shifter according to claim 1, wherein the polarizing prism is a Wollaston prism. 5. The phase biaser according to claim 1, further comprising a packaged steel pipe, the fiber holder, collimating lens, polarizing prism, Faraday rotator, birefringent crystal and reflector are installed in sequence Packaged in steel pipe. 6. phase bias device as claimed in claim 1, is characterized in that, described polarization maintaining fiber adopts large mode area polarization maintaining fiber, doped gain polarization maintaining fiber, large mode area double-clad polarization maintaining fiber and One of the polarization maintaining photonic crystal fibers. 7 . The phase offset device according to claim 1 , wherein the Faraday rotator is a thin-plate Faraday rotator, or a Faraday rotator formed by inserting a magneto-optical crystal into a permanent magnet. 8. A fiber laser that adopts the integrated reflective phase offset device as claimed in claim 1, wherein the fiber laser includes: a fiber beam splitter, a wavelength division multiplexer and a phase offset device; Wherein, the optical fiber splitter includes first to fourth ports; the mode-locked laser pulse is input to the first port of the optical fiber splitter, and the evanescent wave in the polarization-maintaining fiber connected to the first and second ports is coupled into the third port connected to the second port. and the polarization-maintaining fiber of the fourth port, so as to be output from the second and third ports; the mode-locked laser pulse output from the second port is input to a polarization-maintaining fiber of the phase biaser through a wavelength division multiplexer and a gain fiber optical fiber; the mode-locked laser pulse output from the third port is input to another polarization-maintaining fiber of the phase biaser; the mode-locked laser pulse returned from the phase biaser passes through the third port of the fiber beam splitter, and is split from the optical fiber The output of the first port and the fourth port of the bundler. 9. The fiber laser according to claim 8, characterized in that a fiber reflector, or a spatial dispersion compensation device and a reflector, or a filter is attached to the first port. 10. A light-wave-microwave phase detector adopting the integrated reflective phase bias device as claimed in claim 1, characterized in that, the light-wave-microwave phase detector comprises: a balanced photodetector, a circulator , an optical fiber splitter, a wavelength division multiplexer and a phase biaser; wherein the optical fiber splitter includes first to fourth ports; the mode-locked laser pulse enters the first port of the optical fiber splitter through a circulator, and is connected to the first port of the optical fiber splitter The evanescent waves in the polarization-maintaining fiber of the first and second ports are coupled into the polarization-maintaining fiber connecting the third and fourth ports, so as to be output from the second and third ports; the mode-locked laser pulse output from the second port passes through After the wavelength division multiplexer, it is input to a polarization-maintaining fiber connected to the phase biaser; the mode-locked laser pulse output from the third port is input to the other polarization-maintaining fiber of the phase biaser; returned from the phase biaser The mode-locked laser pulses are input to the fiber beam splitter through the second port and the third port respectively, and the mode-locked laser pulses output from the first port respectively enter an input port of the balanced photodetector after passing through the circulator. The mode-locked laser pulse output from the fourth port enters another input port of the balanced photodetector, and a DC level is output from the output port of the balanced photodetector.