Optical amplifier and optical amplification method

Abstract

The application relates to the technical field of optical communication, and particularly provides an optical amplifier and an optical amplification method.The optical amplifier comprises a polarization beam splitting assembly, a bidirectional optical amplification chip, a first transmission light path and a second transmission light path exist between the polarization beam splitting assembly and the optical amplification chip; a first polarization control structure is arranged on the first transmission light path, and a second polarization control structure is arranged on the second transmission light path; the optical amplification method adopts the first polarization control structure and the second polarization control structure to jointly control the polarization state of input light and output light; the application can amplify arbitrary polarized light, realizes low-noise and arbitrary polarization gain effect of a semiconductor optical amplifier, and the amplified light is adjusted into one output light by the polarization control structure and the polarization beam splitting assembly again, so that the amplification effect of the light is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of optical communication technology, specifically to an optical amplifier and an optical amplification method. Background Technology

[0002] Semiconductor optical amplifiers (SOAs) are commonly used in fiber optic communication systems to enhance light intensity. Light experiences loss during transmission within optical fibers, and the magnitude of this loss is proportional to the transmission distance. The primary function of an SOA is to amplify weak light to compensate for this loss during fiber optic transmission and extend the transmission distance.

[0003] Currently, semiconductor optical amplifier (SOA) chips still suffer from issues such as polarization sensitivity and upper limits of saturation gain. Although there are ways to optimize chips to address the polarization sensitivity problem of SOA, the high technical difficulty, long process cycle, and high development cost of these chips make this approach less than ideal.

[0004] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide an optical amplifier and an optical amplification method to solve the problems that urgently need to be solved in this technical field. Summary of the Invention

[0005] The reason why semiconductor optical amplifier chips are currently polarization sensitive is that the chip's amplification effect on light with different polarizations varies, making certain polarization directions more susceptible to amplifier noise, thus increasing the overall noise factor. In view of the shortcomings of the prior art, the purpose of this invention is to provide an optical amplifier and optical amplification method to solve the problems of single-polarization gain chip application and polarization gain adjustment of polarization gain-sensitive chips in the prior art, and to optimize the chip to address the high technical difficulty, long process cycle, and high R&D cost associated with SOA polarization sensitivity.

[0006] To achieve the above and other related objectives, the present invention provides an optical amplifier, including a polarization beam splitter assembly and a bidirectional optical amplification chip, wherein a first transmission optical path and a second transmission optical path exist between the polarization beam splitter assembly and the bidirectional optical amplification chip; a first polarization control structure is provided on the first transmission optical path, and a second polarization control structure is provided on the second transmission optical path; the first polarization control structure includes a first Faraday rotator and a first waveplate; the second polarization control structure includes a second Faraday rotator and a second waveplate.

[0007] The polarization beam splitter is provided with a first port, a second port, a third port and a fourth port. The first port is used to receive incident light, the second port is used to output one of the two input beams with orthogonal polarization directions and transmit the light to the first polarization control structure, the third port is used to output the other of the two input beams with orthogonal polarization directions and transmit the light to the second polarization control structure, and the fourth port is used to output the amplified light.

[0008] The second port of the polarization beam splitter, the first polarization control structure, the bidirectional optical amplifier chip, the second polarization control structure, and the third port of the polarization beam splitter combine to form a series optical path.

[0009] The polarization beam splitter outputs two beams of polarized light with orthogonal polarization states. One beam enters the series optical path from the second port in the forward direction, is amplified and polarized, and then enters the polarization beam splitter from the third port. The other beam of polarized light enters the series optical path from the third port in the reverse direction, is amplified and polarized, and then enters the polarization beam splitter from the second port.

[0010] A second reflector is disposed between the second polarization control structure and the bidirectional optical amplification chip; the second reflector is composed of two triangular mirrors with 90° reflective surfaces, and the two triangular mirrors are arranged opposite each other, so that the second reflector has a 180° reflective surface, realizing optical transmission between the second polarization control structure and the bidirectional optical amplification chip; a first reflector is disposed between the polarization beam splitter component and the second polarization control structure, and the first reflector has a 90° reflective surface, which is used to realize optical transmission between the polarization beam splitter component and the second polarization control structure.

[0011] In one embodiment of the present invention, lenses are provided on both the first and second transmission optical paths, and the lenses are distributed at the bidirectional optical transmission end of the bidirectional optical amplifier chip.

[0012] In one embodiment of the present invention, the first polarization control structure is used to control the polarization state of light on the first transmission optical path so as to output positively polarized light from the second port and negatively polarized light from the third port; the polarization of positively polarized light remains unchanged when passing through the first polarization control structure, and the polarization angle of negatively polarized light decreases by 1 / 2π + gπ (g∈N0) when passing through the structure.

[0013] The first polarization control structure is used to control the polarization state of light on the first transmission optical path. After the positively polarized light output from the second port passes through the first polarization control structure, its polarization remains unchanged, and the principal value angle of the polarization angle when the amplified reverse-polarized light enters the second port is the same as the principal value angle of the polarization angle when it is output from the third port. The second polarization control structure is used to control the polarization state of light on the second transmission optical path. The polarization angle increases by π+kπ (k∈N0), and the polarization angle increases by 1 / 2π+gπ (g∈N0) when the light passes through in the reverse direction.

[0014] The second polarization control structure is used to control the polarization angle of the reverse polarized light output from the third port to be the same as that of the forward polarized light when it enters the bidirectional optical amplifier chip, and to control the principal value angle of the polarization angle to be the same as that before it is amplified when the amplified forward polarized light enters the polarization beam splitter component.

[0015] The first polarization control structure and the second polarization control structure respectively control the polarization rotation angle of the transmitted light by setting the first Faraday rotator and the first wave plate, the second Faraday rotator and the second wave plate to achieve low-noise amplification of arbitrary polarized light input to the optical amplifier by the bidirectional optical amplifier chip.

[0016] In one embodiment of the present invention, the angles of polarization rotation of the first waveplate and the second waveplate with respect to the transmitted light are set to γ ​​and ϕ, respectively, the angle of polarization rotation of the first Faraday rotator with respect to the transmitted light is set to δ1, and the angle of polarization rotation of the second Faraday rotator with respect to the transmitted light is set to δ2.

[0017] The first polarization control structure and the second polarization control structure are respectively set with a first Faraday rotator and a first waveplate, and the second Faraday rotator and the second waveplate have polarization rotation angles for transmitted light such that the following equations all hold:

[0018] δ1=δ2=1 / 4π+(nm)·π, n∈N0;

[0019] γ=1 / 4π+(n+m)·π, n∈N0, m∈N0;

[0020] ϕ=3 / 4π+(r+n)·π, r∈N0, n∈N0.

[0021] In one embodiment of the present invention, the light transmission efficiency of the polarization beam splitter is set to t0, the light transmission efficiency of the first polarization control structure is set to t1, and the light transmission efficiency of the second polarization control structure is set to t2; the gain of the bidirectional optical amplifier chip is set to g0; and the power of the input light is set to P. In The energy of the input light split into two orthogonally polarized beams is set to aP. x bP y The power of the output light after the input light gain is set to P. out The bidirectional optical amplifier chip is set to have gains of g for forward and reverse input light under the same polarization state, respectively. x g y The gain of the optical amplifier for positively polarized light is set to G. x G y The gain of the optical amplifier is set to G. t The polarization-dependent gain of the optical amplifier is set to PDG; the difference between the polarization rotation angle of the transmitted light and the polarization rotation angle under ideal conditions is set to β1.

[0022] The optical amplifier achieves low PDG amplification of arbitrary polarized light by controlling the polarization angle of the input light through a polarization control structure, and ensures that the following equations hold true:

[0023] P In =a·P x +b·P y ;

[0024] P out =∣cosβ1∣·g x ·t0·t1 ·t2·a·P x +∣sin(1 / 2π-β1)∣·t0·t1 ·t2·g y ·b·P y ;

[0025] G x = = |cosβ1|·g x ·t0·t1·t2;

[0026] G y = = |cosβ1|·g y ·t0·t1·t2;

[0027] PDG = G y -G x =g y -g x ;

[0028] G t =G x =G y = |cosβ1|·g x ·t0·t1·t2, if g y =g x .

[0029] An optical amplification method, including the aforementioned optical amplifier, comprises the following steps:

[0030] S1. Using a polarization beam splitter, an arbitrary polarized light beam is split into two beams of orthogonally polarized light. One beam is transmitted through a first transmission optical path and passes through a first polarization control structure in the forward direction, after which its polarization angle increases by β1, where β1 ∈ [0, 1 / 2π]. The other beam is transmitted through a second transmission optical path and passes through a second polarization control structure in the reverse direction, after which its polarization angle decreases by 1 / 2π - β1, where β1 ∈ [0, 2π]. At this point, the polarization states of the two beams of polarized light are the same.

[0031] S2. The light transmitted through the first transmission optical path is polarized by the first polarization control structure, thereby controlling the polarization state of one of the polarized light beams entering the bidirectional optical amplifier chip; the light transmitted through the second transmission optical path is polarized by the second polarization control structure, thereby controlling the polarization state of the other polarized light beam entering the bidirectional optical amplifier chip.

[0032] S3. After being uniformly amplified by the bidirectional optical amplifier chip, the two beams of light are transmitted through each other's transmission optical paths. That is, the light that enters the bidirectional optical amplifier chip through the first transmission optical path enters the second transmission optical path and is then transmitted through the second control structure to adjust its polarization state before entering the polarization beam splitter (1). The light that enters the bidirectional optical amplifier chip through the second transmission optical path enters the first transmission optical path and is then transmitted through the first control structure to adjust its polarization state before reaching the polarization beam splitter. The two beams of polarized light are adjusted to be two orthogonally polarized beams perpendicular to their original polarization states.

[0033] S4. The polarization beam splitter combines two amplified polarized beams into one beam and outputs it from other ports.

[0034] As described above, the optical amplifier and optical amplification method of the present invention have the following beneficial effects:

[0035] This invention uses a polarization beam splitter, an optical amplifier chip, a Faraday rotator, a waveplate, a mirror, and a lens as basic components. These components are combined to form an optical amplifier, enabling SOA (Optical Optical Amplifier) ​​to achieve low-noise, uniform gain for arbitrary polarized light under relatively simple structural and technological conditions. This effectively reduces technical difficulty and R&D costs, shortens the process cycle, and has good market application prospects. The invention uses a polarization beam splitter in conjunction with a first polarization control structure and a second polarization control structure to adjust the polarization direction of the light. The input light is split into two beams with different polarization directions, amplified separately, and then combined into a single output beam. This allows the semiconductor optical amplifier to amplify arbitrary polarized light, achieving low noise and arbitrary polarization gain. The amplified light is then adjusted again by the polarization control structure and the polarization beam splitter to form a single output beam, effectively improving the amplification effect. Attached Figure Description

[0036] Figure 1 The diagram shown is a schematic representation of the structure of the optical amplifier disclosed in this invention.

[0037] Figure 2 The diagram shown is a schematic diagram of the optical amplifier disclosed in Example 2.

[0038] Figure 3 The diagram shown is a schematic diagram of the optical amplifier disclosed in Example 3.

[0039] Figure 4 The diagram shown is a schematic diagram of the optical amplifier disclosed in Example 4.

[0040] Figure 5 The diagram shown is a schematic diagram of the optical amplifier disclosed in Example 5.

[0041] Component designation explanation

[0042] 1. Polarization beam splitter assembly; 2. Optical amplifier chip; 3. First Faraday rotator; 4. First waveplate; 5. Second Faraday rotator; 6. Second waveplate; 7. Second reflector; 8. Lens; 9. Third waveplate; 8. First polarization control structure; 11. Second polarization control structure; 12. First port; 13. Second port; 14. Third port; 15. Fourth port; 16. First reflector; 10. Detailed Implementation

[0043] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0044] Please see Figures 1 to 5 It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the implementation of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed in this invention.

[0045] Example 1: This example provides an optical amplifier, including a polarization beam splitter 1 and a bidirectional optical amplification chip 2. The polarization beam splitter 1 includes a multilayer dielectric film stack or a birefringent crystal, wherein the multilayer dielectric film stack is a multilayer metal oxide film system, which refers to a multilayer structure formed by alternating deposition of two or more metal oxides, and can be prepared by methods such as physical vapor deposition (PVD) or chemical vapor deposition (CVD). The polarization beam splitter 1 is equipped with a first reflector 10 for reflecting the split beam.

[0046] A first transmission optical path and a second transmission optical path exist between the polarization beam splitter assembly 1 and the bidirectional optical amplification chip 2. Lenses 8 are provided on both the first and second transmission optical paths, distributed at the bidirectional optical transmission ends of the bidirectional optical amplification chip 2. A first polarization control structure 11 is provided on the first transmission optical path, and a second polarization control structure 12 is provided on the second transmission optical path. The first polarization control structure 11 includes a first Faraday rotator 3 and a first waveplate 4. The first waveplate 4 is configured as a 1 / 8 waveplate, meaning it has a deflection angle of 360° * 1 / 8, or 45°. The second polarization control structure 12 includes a second Faraday rotator 5 and a second waveplate 6. The second waveplate 6 is configured as a 3 / 8 waveplate, meaning it has a deflection angle of 360° * 3 / 8, or 135°. A first port 13 is provided on the polarization beam splitter assembly 1. The polarization beam splitter 1 has a second port 14, a third port 15, and a fourth port 16. The first port 13 is used to receive incident light. The second port 14 is used to output one of the two input beams with orthogonal polarization directions and transmit the light to the first polarization control structure 11. The third port 15 is used to output the other of the two input beams with orthogonal polarization directions and transmit the light to the second polarization control structure 12. The fourth port 16 is used to output the amplified light. The second port 14, the first polarization control structure 11, the bidirectional optical amplification chip 2, the second polarization control structure 12, and the third port 15 of the polarization beam splitter 1 form a series optical path.

[0047] The amplification of polarized light by the semiconductor optical amplifier is calculated using the following formula:

[0048] P in =a·P x + b·P y ;

[0049] P out =a·t0·t1·t2·g0·P x + b·t0· t1 ·t2·g0··P y ;

[0050] t0 is the light transmission efficiency of polarization beam splitter 1, t1 is the light transmission efficiency of the first polarization control structure 11, t2 is the light transmission efficiency of the second polarization control structure 12, g0 is the gain of the bidirectional optical amplifier chip 2, and the input optical power is P. in The output optical power is P out ;aP x bP y The energy of the input light split into two orthogonally polarized beams, respectively; the output optical power P out = t0· t1·t2 ·g0·P in The light input to the optical amplifier can be amplified by arbitrary polarization.

[0051] When the polarization rotation angle of the polarization control structure is non-ideal; when light passes through the first polarization control structure 11 in the forward direction, the polarization angle increases by β1+gπg∈N0, β1∈[0,1 / 2π], and decreases by 1 / 2π-β1+dπd∈N0, β1∈[0,1 / 2π] when light passes through the second polarization control structure 12 in the reverse direction, the polarization angle decreases by 1 / 2π-β1+eπe∈N0, β1∈[0,1 / 2π], and increases by π-β1+fπf∈N0, β1∈[0,1 / 2π] when light passes through the second polarization control structure 12 in the forward direction; at this time, the gain effect of the optical amplification chip on the light is:

[0052] P In =a·P x +b·P y ;

[0053] P out = cosβ1·g x ·t0·t1 ·t2·a·P x +cosβ1·t0· t1 ·t2·g y ·b·P y θ∈[0,2π];

[0054] G x = = cosβ1·g x ·t0·t1·t2;

[0055] G y = = cosβ1·g y ·t0·t1·t2;

[0056] Where t0 is the light transmission efficiency of polarization beam splitter 1, t1 is the light transmission efficiency of the first polarization control structure 11, t2 is the light transmission efficiency of the second polarization control structure 12, g0 is the light gain of the bidirectional optical amplifier chip 2, and P In The power of the input light, aP x bP y These represent the energy of the input light split into two orthogonally polarized beams, P, and P, respectively. out β1 is the power of the output light after the input light gain, and β1 is the angle of polarization rotation after the light passes through the first polarization control structure 11 in the forward direction and the angle of polarization rotation after the light passes through the second polarization control structure 12 in the reverse direction; g x g y These represent the gains of the two bidirectional optical amplifier chips 2 for the forward and reverse input light in the same polarization state, respectively; G x G yThese represent the gains of the optical amplifier for two beams of orthogonally polarized light, respectively.

[0057] The PGR of the optical amplifier for the input light at this time is:

[0058] PGR= G y -G x =g y -g x ;

[0059] When the chip has equal gain for both forward and reverse input light under the same polarization state, i.e. g x =g y The effect of the polarization control structure on the optical amplifier is as follows:

[0060] PDR=0;

[0061] G t =G x =G y = cosβ1·g x ·t0·t1·t2;

[0062] The G t This represents the gain of the optical amplifier on light.

[0063] The polarization beam splitter 1 outputs two beams of polarized light with orthogonal polarization states. One beam enters the series optical path from the second port 14 in the forward direction, is amplified and polarized, and then enters the polarization beam splitter 1 from the third port 15. The other beam of polarized light enters the series optical path from the third port 15 in the reverse direction, is amplified and polarized, and then enters the polarization beam splitter 1 from the second port 14.

[0064] A second reflector 7 is disposed between the second polarization control structure 12 and the bidirectional optical amplification chip 2. The second reflector 7 is composed of a reflector with a 180° reflective surface, or the second reflector 7 is composed of two triangular mirrors with 90° reflective surfaces. The two triangular mirrors are arranged opposite each other, so that the second reflector 7 has a 180° reflective surface, realizing the optical transmission between the second polarization control structure 12 and the bidirectional optical amplification chip. A first reflector 10 is disposed between the polarization beam splitter assembly 1 and the second polarization control structure 12. The first reflector 10 has a 90° reflective surface and is used to realize the optical transmission between the polarization beam splitter assembly 1 and the second polarization control structure 12.

[0065] The first polarization control structure 11 controls the polarization state of light on the first transmission optical path, so as to output positively polarized light from the second port 14 and negatively polarized light from the third port 15. Positively polarized light passes through the first polarization control structure 11 with its polarization unchanged, while negatively polarized light passes through with its polarization angle decreasing by 1 / 2π + gπg∈N0. The first polarization control structure 11 controls the positively polarized light output from the second port 14 to maintain its polarization unchanged after passing through the first polarization control structure 11, and controls the principal value angle of the polarization angle of the amplified negatively polarized light entering the second port 14 to be the same as the principal value angle of the polarization angle output from the third port 15. The second polarization control structure 12 controls the polarization state of light on the second transmission optical path. Light passing positively through the second polarization control structure 12 has its polarization angle increased by π + kπk∈N0, and light passing negatively has its polarization angle increased by 1 / 2π + kπk∈N0. gπg∈N0; The second polarization control structure is used to control the polarization angle of the reverse polarized light output from the third port 15 to be the same as that of the forward polarized light when it enters the bidirectional optical amplifier chip 2, and to control the principal value angle of the polarization angle of the amplified forward polarized light to be the same as that before amplification when it enters the polarization beam splitter component 1; The first polarization control structure 11 and the second polarization control structure 12 respectively control the polarization rotation angle of the transmitted light by setting the first Faraday rotator 3 and the first wave plate 4, the second Faraday rotator 5 and the second wave plate 6 to perform low-noise amplification of arbitrary polarized light input to the optical amplifier by the bidirectional optical amplifier chip 2.

[0066] Let the angles of polarization rotation of the first waveplate 4 and the second waveplate 6 relative to the transmitted light be γ and ϕ, respectively; let the angle of polarization rotation of the first Faraday rotator 3 relative to the transmitted light be δ1; and let the angle of polarization rotation of the second Faraday rotator 5 relative to the transmitted light be δ2. The first polarization control structure 11 and the second polarization control structure 12 shall respectively set the angles of polarization rotation of the first Faraday rotator 3 and the first waveplate 4, and the second Faraday rotator 5 and the second waveplate 6 relative to the transmitted light such that the following equations all hold:

[0067] 1δ1=δ2=1 / 4π+nm·π, n∈N0;

[0068] 2γ=1 / 4π+n+m·π, n∈N0, m∈N0;

[0069] 3ϕ=3 / 4π+r+n·π, r∈N0, n∈N0.

[0070] The light transmission efficiency of the polarization beam splitter 1 is set to t0, the light transmission efficiency of the first polarization control structure 11 is set to t1, and the light transmission efficiency of the second polarization control structure 12 is set to t2; the gain of the bidirectional optical amplifier chip 2 is set to g0; and the power of the input light is set to P. In The energy of the input light split into two orthogonally polarized beams is set to aP. xbP y The power of the output light after the input light gain is set to P. out The bidirectional optical amplifier chip 2 is set to have gains of g for forward and reverse input light under the same polarization state, respectively. x g y The gain of the optical amplifier for positively polarized light is set to G. x G y The gain of the optical amplifier is set to G. t The PDG is the polarization-dependent gain of the optical amplifier; the difference between the polarization rotation angle of the transmitted light and the polarization rotation angle under ideal conditions is set to β1; the optical amplifier controls the polarization angle of the input light by setting the polarization control structure to achieve low PDG amplification of arbitrary polarized light, and the following equations all hold:

[0071] 1P In =a·P x +b·P y ;

[0072] 2P out =∣cosβ1∣·g x ·t0·t1 ·t2·a·P x +∣sin1 / 2π-β1∣·t0·t1 ·t2·g y ·b·P y ;

[0073] 3G x = = |cosβ1|·g x ·t0·t1·t2;

[0074] 4G y = = |cosβ1|·g y ·t0·t1·t2;

[0075] 5PDG = G y -G x =g y -g x ;

[0076] 6G t =G x =G y = |cosβ1|·g x ·t0·t1·t2, if g y =g x .

[0077] This invention uses a polarization beam splitter 1, a bidirectional optical amplifier chip 2, a Faraday rotator 3, a waveplate 4, a reflector, and a lens 8 as basic components. These basic components are designed together to form an optical amplifier, enabling SOA to achieve low noise and uniform gain for light of arbitrary polarization under relatively simple structural and process conditions. This effectively reduces technical difficulty and R&D costs, shortens the process cycle, and has good market application prospects.

[0078] Example 2: This example provides an optical amplification method, including the optical amplifier described in Example 1, comprising the following steps:

[0079] S1. Using a polarization beam splitter 1, an arbitrary polarized light is split into two beams of orthogonally polarized light. One beam is transmitted through a first transmission optical path and passes through a first polarization control structure 11 in the forward direction, after which its polarization angle increases by β1, where β1 ∈ [0, 1 / 2π]. The other beam is transmitted through a second transmission optical path and passes through a second polarization control structure 12 in the reverse direction, after which its polarization angle decreases by 1 / 2π - β1, where β1 ∈ [0, 2π]. At this time, the polarization states of the two beams of polarized light are the same.

[0080] S2. The light transmitted through the first transmission optical path is polarized by the first polarization control structure 11, thereby controlling the polarization state of one of the polarized light beams entering the bidirectional optical amplifier chip 2; the light transmitted through the second transmission optical path is polarized by the second polarization control structure 12, thereby controlling the polarization state of the other polarized light beam entering the bidirectional optical amplifier chip 2.

[0081] S3. After being uniformly amplified by the bidirectional optical amplifier chip 2, the two beams of light are transmitted through each other's transmission optical paths. That is, the light that enters the bidirectional optical amplifier chip 2 through the first transmission optical path enters the second transmission optical path and is then transmitted through the second control structure after its polarization state is readjusted before entering the polarization beam splitter assembly (1). The light that enters the bidirectional optical amplifier chip 2 through the second transmission optical path enters the first transmission optical path and is then transmitted through the first control structure after its polarization state is readjusted before reaching the polarization beam splitter assembly 1. The two beams of polarized light are adjusted to be two orthogonally polarized beams perpendicular to their original polarization states.

[0082] S4. The polarization beam splitter 1 combines two amplified polarized beams into one beam and outputs it from other ports.

[0083] The design of the semiconductor optical amplifier can be implemented in various ways. By changing the polarization rotation angles of the Faraday rotator and waveplate, increasing the number of waveplates to control the polarization direction, and placing mirrors between optical elements to form a closed-loop optical path through phase reflection between the optical paths, the relationship between the polarization displacements of the three optical elements can be obtained from the above formulas. Furthermore, the relationship between the first polarization control structure 11 and the second polarization control structure 12 and the polarization rotation angle of the transmitted light can be obtained.

[0084] Specifically, the Faraday rotator can rotate the positively polarized light by a fixed angle and rotate the reverse polarized light passing through it by a fixed angle.

[0085] The waveplate can deflect bidirectional light passing through it by a fixed angle in the same direction;

[0086] When the first waveplate 4 in the first polarization control structure 11 and the second waveplate 6 in the second polarization control structure 12 cooperate, the polarization direction angle of the light passing through the first Faraday rotator 3 and the first waveplate 4 in the forward direction is f·π, f∈N0; while the polarization direction of the light passing through in the reverse direction will be 1 / 4π+f+gπ, f∈N0, g∈N0.

[0087] When the second Faraday rotator 5 and the second wave plate 6 are combined, the polarization angle of the light passing through the second Faraday rotator 5 and the second wave plate 6 in the forward direction is m·π, m∈N0; while the polarization direction of the light passing through in the reverse direction will be 1 / 2π+n·π, n∈N0.

[0088] The input light is split into two polarized beams before entering the bidirectional optical amplifier chip 2, and the polarization directions are exactly the same.

[0089] The bidirectional optical amplifier chip 2 is used to amplify two input beams with the same polarization direction with the same gain, without degrading the gain and noise figure.

[0090] The output light from the bidirectional optical amplifier chip 2 passes sequentially through the second wave plate 6, the second Faraday rotator 5, the first wave plate 4, and the first Faraday rotator 3. At this time, the polarization state of the two beams of light is adjusted to be two output beams with orthogonal polarization directions.

[0091] In the two output light paths within the closed loop, the polarization direction of the output light from the first Faraday rotator 3 to the polarization beam splitter 1 cannot be transmitted through the polarization beam splitter 1 and is reflected.

[0092] Within the closed loop, the polarization direction of the output light from the second Faraday rotator 5 to the polarization beam splitter 1 can now pass through the polarization beam splitter 1 and coincide with the path of the other polarized light, thus combining into a single output light.

[0093] Example 3, please refer to Figure 3 Based on embodiments 1 and 2, this embodiment provides an optical amplifier, including a polarization beam splitter 1, a bidirectional optical amplification chip 2, and a second reflector 7. The polarization beam splitter 1 is equipped with a first reflector for reflecting the split beam. Lenses 8 are provided on the bidirectional optical transmission ends of the optical amplification chip 2. The polarization control structure 11 and polarization control structure 12 are attached to the polarization beam splitter 1.

[0094] A first transmission optical path and a second transmission optical path exist between the polarization beam splitter assembly 1 and the bidirectional optical amplification chip 2. A second reflector 7 is simultaneously located at the ends of both the first and second transmission optical paths. The polarization beam splitter assembly is used to separate unpolarized input light into two beams with orthogonal polarization. A first polarization control structure 11 is provided on the first transmission optical path. The first polarization control structure 11 includes a first Faraday rotator 3 and a first waveplate 4. The first waveplate 4 is configured as a 1 / 8 waveplate, meaning it has a deflection angle of 360° * 1 / 8, or 45°. The first polarization control structure 11 utilizes the irreversibility of the optical path provided by the Faraday rotator 3 and the reversibility of the optical path provided by the first waveplate 4. The polarization state of the transmitted light is controlled; a second polarization control structure 12 is provided on the second transmission optical path. The second polarization control structure 12 includes a second Faraday rotator 5 and a second waveplate 6. The second waveplate 6 is set as a 3 / 8 waveplate, that is, the second waveplate 6 has a deflection angle of 360°*3 / 8, that is, a deflection angle of 135°. The second polarization control structure 12 uses the irreversibility of the optical path of the second Faraday rotator 5 and the reverse reversibility of the optical path of the second waveplate 6 to control the polarization state of the transmitted light; the output light is then combined into one beam by the polarization separation component 1 and output.

[0095] The first Faraday rotator 3 and the second Faraday rotator 5 are the same 1 / 8 Faraday rotator, which is attached to the end face of the second port 14 and the third port 15 region of the polarization beam splitter 1. The second waveplate 6 is attached to the 1 / 8 Faraday rotator located in the region of the second port 14, and the first waveplate 4 is attached to the 1 / 8 Faraday rotator located in the region of the third port 15. The first port 13 of the polarization beam splitter 1 is sequentially coupled with the 1 / 8 Faraday rotator, the second waveplate 6, the second reflector 7, the lens 8, the bidirectional optical amplification chip 2, the lens 8, the first waveplate 4, and the third port 15 of the polarization beam splitter 1 to form a closed-loop optical path.

[0096] The input light is split into two beams of polarized light with orthogonal polarization directions by the polarization beam splitter 1. The beam output from the third port 15 is defined as polarized light one, and the beam output from the second port 14 is defined as polarized light two. After the polarized light one is output from the third port 15, it passes through a 1 / 8 Faraday rotator and a second wave plate 4, and its polarization direction will be the same as the original polarization direction. After the second polarized light is output from the second port 14, it passes through a 1 / 8 Faraday rotator and a first wave plate 6, and its polarization direction will be perpendicular to the original polarization direction. At this time, the polarization directions of the first polarized light and the second polarized light are the same. The polarization directions of polarized light one and polarized light two are the same before entering the lens 8. After being reflected by the two triangular mirrors, the second polarized light is refracted by the lens 8 and enters the bidirectional optical amplifier chip 2 for amplification. The second polarized light is output from the 1 / 8 wave plate, refracted by the lens 8, and then enters the bidirectional optical amplifier chip 2 for amplification. The amplified polarized light is defined as the first polarized light, and the amplified polarized light is defined as the second polarized light. The second polarized light is output from the bidirectional optical amplification chip 2, passes through lens 8, and then to the first waveplate 4. After passing through the first waveplate 4 and the 1 / 8 Faraday rotator, it enters the polarization beam splitter assembly 1 through the third port 15. At this time, its polarization direction is perpendicular to the polarization direction of the second polarized light. After being output from the bidirectional optical amplification chip 2, the second polarized light passes through lens 8 and is reflected by two triangular mirrors to the second waveplate 6. After the polarization direction is adjusted by the second waveplate 6 and the 1 / 8 Faraday rotator, it exits through the second port 15. 4. The light enters the polarization beam splitter 1. At this time, the polarization direction of the second polarized light is perpendicular to the polarization direction of the first polarized light. The polarization directions of the first polarized light and the second polarized light entering the polarization beam splitter 1 are perpendicular to each other. The polarization direction of the first polarized light cannot pass through the polarization beam splitter 1. After being reflected by the reflective surface on the polarization beam splitter 1, it is output from the fourth port 16. The polarization direction of the second polarized light can pass through the polarization beam splitter 1 and be output from port 16. The path of the first polarized light after being reflected by the gain polarization beam splitter completely coincides with that of the second polarized light after being gained polarization beam splitter, and they are combined into a single output beam.

[0097] Example 4, please refer to Figure 4 Based on embodiment 3, this embodiment adds a third waveplate 9, which is a 1 / 8 waveplate. The third waveplate 9 is attached to the fourth port 16 of the polarization beam splitter assembly, which can rotate the polarization state of the amplified light by 1 / 4π, thereby achieving polarization-preserving amplification of the light.

[0098] Example 5, please refer to Figure 5 Based on embodiments 1 and 2, this embodiment provides an optical amplifier, including a polarization beam splitter 1, a bidirectional optical amplification chip 2, and a second reflector 7. The polarization beam splitter 1 is equipped with a first reflector 10 for reflecting the split beam. The bidirectional optical transmission end of the optical amplification chip 2 is provided with a lens 8.

[0099] A first transmission optical path and a second transmission optical path exist between the polarization beam splitter assembly 1 and the bidirectional optical amplification chip 2. A second reflector 7 is simultaneously located at the ends of both the first and second transmission optical paths. The polarization beam splitter assembly is used to separate unpolarized input light into two beams with orthogonal polarization. A first polarization control structure 11 is provided on the first transmission optical path. The first polarization control structure 11 includes a first Faraday rotator 3 and a first waveplate 4. The first waveplate 4 is configured as a 1 / 8 waveplate, meaning it has a deflection angle of 360° * 1 / 8, or 45°. The first polarization control structure 11 utilizes the irreversibility of the optical path provided by the Faraday rotator 3 and the reversibility of the optical path provided by the first waveplate 4. To control the polarization state of the transmitted light; a second polarization control structure 12 is provided on the second transmission optical path. The second polarization control structure 12 includes a second Faraday rotator 5 and a second waveplate 6. The second waveplate 6 is set as a 3 / 8 waveplate, that is, the second waveplate 6 has a deflection angle of 360°*3 / 8, that is, a deflection angle of 135°. The second polarization control structure 12 uses the irreversibility of the optical path of the second Faraday rotator 5 and the reverse reversibility of the optical path of the second waveplate 6 to control the polarization state of the transmitted light; the output light is then combined into one beam by the polarization separation component 1 and output.

[0100] The first Faraday rotator 3 and the second Faraday rotator 5 are the same 1 / 8 Faraday rotator, which simultaneously corresponds to the second port 14 and the third port 15 of the polarization beam splitter assembly 1. The second waveplate 6 is attached to the 1 / 8 Faraday rotator located in the region of the second port 14, and the first waveplate 4 is attached to the 1 / 8 Faraday rotator located in the region of the third port 15. The polarization control structure 11 and the polarization control structure 12 are fixed together. The second reflector 7 is composed of two triangular mirrors with 90° reflective surfaces, and the reflective surfaces of the two triangular mirrors are arranged opposite each other, so that the second reflector 7 has a 180° reflective surface. The first port 13 of the polarization beam splitter assembly 1 is sequentially coupled with the 1 / 8 Faraday rotator, the second waveplate 6, the two triangular mirrors, the lens 8, the bidirectional optical amplification chip 2, the lens 8, the first waveplate 4, and the third port 15 of the polarization beam splitter assembly 1 to form a series optical path.

[0101] The input light is split into two beams of polarized light with orthogonal polarization directions by the polarization beam splitter 1. The beam output from the third port 15 is defined as polarized light one, and the beam output from the second port 14 is defined as polarized light two. After the polarized light one is output from the third port 15, it passes through a 1 / 8 Faraday rotator and a second wave plate 4, and its polarization direction will be the same as the original polarization direction. After the second polarized light is output from the second port 14, it passes through a 1 / 8 Faraday rotator and a first wave plate 6, and its polarization direction will be perpendicular to the original polarization direction. At this time, the polarization directions of the first polarized light and the second polarized light are the same. The polarization directions of polarized light one and polarized light two are the same before entering the lens 8. After being reflected by the two triangular mirrors, the second polarized light is refracted by the lens 8 and enters the bidirectional optical amplifier chip 2 for amplification. The second polarized light is output from the 1 / 8 wave plate, refracted by the lens 8, and then enters the bidirectional optical amplifier chip 2 for amplification. The amplified polarized light is defined as the first polarized light, and the amplified polarized light is defined as the second polarized light. The second polarized light is output from the bidirectional optical amplification chip 2, passes through lens 8, and then to the first waveplate 4. After passing through the first waveplate 4 and the 1 / 8 Faraday rotator, it enters the polarization beam splitter assembly 1 through the third port 15. At this time, its polarization direction is perpendicular to the polarization direction of the second polarized light. After being output from the bidirectional optical amplification chip 2, the second polarized light passes through lens 8 and is reflected by two triangular mirrors to the second waveplate 6. After the polarization direction is adjusted by the second waveplate 6 and the 1 / 8 Faraday rotator, it exits through the second port 15. 4. The light enters the polarization beam splitter 1. At this time, the polarization direction of the second polarized light is perpendicular to the polarization direction of the first polarized light. The polarization directions of the first polarized light and the second polarized light entering the polarization beam splitter 1 are perpendicular to each other. The polarization direction of the first polarized light cannot pass through the polarization beam splitter 1. After being reflected by the reflective surface on the polarization beam splitter 1, it is output from the fourth port 16. The polarization direction of the second polarized light can pass through the polarization beam splitter 1 and be output from port 16. The path of the first polarized light after being reflected by the gain polarization beam splitter completely coincides with that of the second polarized light after being gained polarization beam splitter, and they are combined into a single output beam.

[0102] In summary, this invention uses a polarization beam splitter 1, an optical amplifier chip 2, a Faraday rotator, a waveplate, a reflector, and a lens 8 as basic components. These components are combined to form an optical amplifier, enabling the SOA to achieve low-noise, uniform gain for arbitrary polarized light under relatively simple structural and technological conditions. This effectively reduces technical difficulty and R&D costs, shortens the process cycle, and has good market application prospects. This invention adjusts the polarization direction of light by cooperating with the polarization beam splitter 1, the first polarization control structure 11, and the second polarization control structure 12. The input light is split into two beams with different polarization directions, amplified separately, and then combined into a single output beam. This allows the semiconductor optical amplifier to amplify arbitrary polarized light, achieving low noise and arbitrary polarization gain. The amplified light is then adjusted again by the polarization control structure and the polarization beam splitter to form a single output beam, effectively improving the amplification effect. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial application value.

[0103] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. An optical amplifier, characterized in that, The device includes a polarization beam splitter (1) and a bidirectional optical amplifier chip (2). A first transmission optical path and a second transmission optical path exist between the polarization beam splitter (1) and the bidirectional optical amplifier chip (2). A first polarization control structure (11) is provided on the first transmission optical path, and a second polarization control structure (12) is provided on the second transmission optical path. The first polarization control structure (11) includes a first Faraday rotator (3) and a first waveplate (4). The second polarization control structure (12) includes a second Faraday rotator (5) and a second waveplate (6). The polarization beam splitter assembly (1) is provided with a first port (13), a second port (14), a third port (15), and a fourth port (16). The first port (13) is used to receive incident light, the second port (14) is used to output one of the two input beams with orthogonal polarization directions and transmit the light to the first polarization control structure (11); the third port (15) is used to output the other of the two input beams with orthogonal polarization directions and transmit the light to the second polarization control structure (12); and the fourth port (16) is used to output the amplified light. The second port (14) of the polarization beam splitter, the first polarization control structure (11), the bidirectional optical amplifier chip (2), the second polarization control structure (12), and the third port (15) of the polarization beam splitter (1) are combined to form a series optical path; The polarization beam splitter (1) outputs two beams of polarized light with orthogonal polarization states. One beam enters the series optical path from the second port (14) in the forward direction, is amplified and polarized, and then enters the polarization beam splitter (1) from the third port (15). The other beam of polarized light enters the series optical path from the third port (15) in the reverse direction, is amplified and polarized, and then enters the polarization beam splitter (1) from the second port (14). A second reflector (7) is provided between the second polarization control structure (12) and the bidirectional optical amplifier chip (2); the second reflector (7) is composed of two triangular mirrors with 90° reflective surfaces, and the two triangular mirrors are arranged opposite to each other so that the second reflector (7) has a 180° reflective surface, thereby realizing the optical transmission between the second polarization control structure (12) and the bidirectional optical amplifier chip; a first reflector (10) is provided between the polarization beam splitter component (1) and the second polarization control structure (12), and the first reflector (10) has a 90° reflective surface, which is used to realize the optical transmission between the polarization beam splitter component (1) and the second polarization control structure (12).

2. The optical amplifier according to claim 1 is characterized in that: Lenses (8) are provided on both the first and second transmission optical paths, and the lenses (8) are distributed at the bidirectional optical transmission end of the bidirectional optical amplifier chip (2).

3. The optical amplifier according to claim 1 is characterized in that: The first polarization control structure (11) is used to control the polarization state of light on the first transmission optical path so as to output positively polarized light from the second port (14) and negatively polarized light from the third port (15); the polarization of positively polarized light remains unchanged when passing through the first polarization control structure (11), and the polarization angle of negatively polarized light decreases by 1 / 2π + gπ (g∈N0). The first polarization control structure (11) is used to control the polarization state of light on the first transmission optical path. After the positively polarized light output from the second port (14) passes through the first polarization control structure (11), the polarization remains unchanged. The principal value angle of the polarization angle when the amplified reversely polarized light enters the second port (14) is the same as the principal value angle of the polarization angle when it is output from the third port (15). The second polarization control structure (12) is used to control the polarization state of light on the second transmission optical path. The polarization angle of light passing through the second polarization control structure (12) in the positive direction increases by π+kπ (k∈N0), and the polarization angle of light passing through in the reverse direction increases by 1 / 2π+gπ (g∈N0). The second polarization control structure is used to control the polarization angle of the reverse polarized light output from the third port (15) to be the same as that of the forward polarized light when it enters the bidirectional optical amplifier chip (2), and to control the principal value angle of the polarization angle to be the same as that before it is amplified when the amplified forward polarized light enters the polarization beam splitter assembly (1). The first polarization control structure (11) and the second polarization control structure (12) control the polarization rotation angle of the transmitted light by setting the first Faraday rotator (3) and the first wave plate (4), the second Faraday rotator (5) and the second wave plate (6), respectively. The bidirectional optical amplifier chip (2) amplifies the arbitrary polarized light of the input optical amplifier with low noise.

4. The optical amplifier according to claim 3, characterized in that: The first wave plate (4) and the second wave plate (6) are set to rotate by γ and ϕ respectively, the first Faraday rotator (3) is set to rotate by δ1, and the second Faraday rotator (5) is set to rotate by δ2. The first polarization control structure (11) and the second polarization control structure (12) are respectively set with a first Faraday rotator (3) and a first wave plate (4), a second Faraday rotator (5) and a second wave plate (6). The polarization rotation angle of the transmitted light must be such that the following equations all hold: (1) δ1=δ2=1 / 4π+(nm)·π, n∈N0; (2) γ=1 / 4π+(n+m)·π, n∈N0, m∈N0; (3) ϕ=3 / 4π+(r+n)·π, r∈N0, n∈N0.

5. The optical amplifier according to claim 4, characterized in that: The light transmission efficiency of the polarization beam splitter (1) is set to t0, the light transmission efficiency of the first polarization control structure (11) is set to t1, and the light transmission efficiency of the second polarization control structure (12) is set to t2; the gain of the bidirectional optical amplifier chip (2) is set to g0; and the power of the input light is set to P. In The energy of the input light split into two orthogonally polarized beams is set to aP. x bP y The power of the output light after the input light gain is set to P. out The bidirectional optical amplifier chip (2) is configured to have gains of g for forward and reverse input light under the same polarization state, respectively. x g y The gain of the optical amplifier for positively polarized light is set to G. x G y The gain of the optical amplifier is set to G. t The polarization-dependent gain of the optical amplifier is set to PDG; the difference between the polarization rotation angle of the transmitted light and the polarization rotation angle under ideal conditions is set to β1. The optical amplifier achieves low PDG amplification of arbitrary polarized light by controlling the polarization angle of the input light through a polarization control structure, and ensures that the following equations hold true: (1)P In =a·P x +b·P y ; (2)P out =∣cosβ1∣·g x ·t0·t1 ·t2·a·P x +∣sin(1 / 2π-β1)∣·t0· t1 ·t2·g y ·b·P y ; (3) G x = = ∣cosβ1∣·g x ·t0·t1 ·t2; (4) G y = = ∣cosβ1∣·g y ·t0·t1 ·t2; (5)PDG= G y -G x =g y -g x ; (6)G t =G x =G y = ∣cosβ1∣·g x ·t0·t1 ·t2,if g y =g x 。 6. An optical amplification method, comprising the optical amplifier according to any one of claims 1-5, characterized in that: Includes the following steps: S1. Using a polarization beam splitter (1), an arbitrary polarized light is split into two beams of orthogonally polarized light. One beam passes through the first transmission optical path and then through the first polarization control structure (11) in the forward direction, after which the polarization angle increases by β1, where β1 ∈ [0, 1 / 2π]. The other beam passes through the second transmission optical path and then passes through the second polarization control structure (12) in the reverse direction, after which the polarization angle decreases by 1 / 2π - β1, where β1 ∈ [0, 2π]. At this time, the polarization states of the two beams of polarized light are the same. S2. The light transmitted through the first transmission optical path is polarized by the first polarization control structure (11), thereby controlling the polarization state of one of the polarized light beams entering the bidirectional optical amplifier chip (2); the light transmitted through the second transmission optical path is polarized by the second polarization control structure (12), thereby controlling the polarization state of the other polarized light beam entering the bidirectional optical amplifier chip (2). S3. After being uniformly amplified by the bidirectional optical amplifier chip (2), the two beams of light are transmitted through the transmission optical path of each other. That is, the light that enters the bidirectional optical amplifier chip (2) through the first transmission optical path enters the second transmission optical path and enters the polarization beam splitter component (1) after the polarization state is adjusted again by the second control structure. The light that enters the bidirectional optical amplifier chip (2) through the second transmission optical path enters the first transmission optical path and enters the polarization beam splitter component (1) after the polarization state is adjusted again by the first control structure. The two beams of polarized light are adjusted to be two beams of orthogonal polarized light that are perpendicular to the original polarization state. S4, Polarization beam splitter (1) combines two amplified polarized beams into one beam and outputs it from other ports.

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