CN107534495A

CN107534495A - A kind of wavelength locker, wavelength locking method and device

Info

Publication number: CN107534495A
Application number: CN201580079093.4A
Authority: CN
Inventors: 韦逸嘉; 李良川; 赵平; 吴波
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2015-04-22
Filing date: 2015-04-22
Publication date: 2018-01-02
Anticipated expiration: 2035-04-22
Also published as: WO2016169007A1; CN107534495B

Abstract

The embodiment of the present invention provides a kind of wavelength locker, wavelength locking method and device, to solve that at present when wave length shift is larger, correct frequency shift (FS) can not be detected, and can not accomplish the high accuracy in full band range.Detection process circuit in the wavelength locker, for the optical signal for being reflected and being transmitted according to the first F P etalons, and the 2nd F P etalons reflect and the optical signal of transmission, the pin electric current of the laser is adjusted so that the frequency shift (FS) of the laser is in error range；The frequency range of the range of linearity in a cycle of the transfer function of the first F P etalons is not more than the minimum detection precision of demand；Twice of the Cycle Length of the transfer function of the 2nd F P etalons not less than the maximum of the frequency shift (FS) of the laser；The frequency of the optical signal of the preset wavelength is located at the range of linearity of the transfer function of the first F P etalons and the transfer function of the 2nd F P etalons.

Description

Wavelength locker, wavelength locking method and device

Technical Field

The present invention relates to the field of communications technologies, and in particular, to a wavelength locker, a wavelength locking method, and a wavelength locking device.

Background

In the current Dense Wavelength Division Multiplexing (DWDM), a Wavelength tunable laser is generally used as a laser at a transmitting end for universality, a Wavelength interval is 50GHz, if the Wavelength of the laser at the transmitting end drifts, channel crosstalk may be caused, and transmission cost is generated, under such a condition, a high requirement is provided for the Wavelength stability of the laser, and the maximum frequency deviation value of the laser with the highest precision at present does not exceed ± 2.5GHz in the whole life cycle, that is, in the end point process from factory to service life. If applied in a system with lower wavelength spacing and baud rate, such as a future super-subcarrier (super-subcarrier) system, each subband is spaced only about 2.5GHz apart, with a baud rate greater than 2Gbaud, which may result in transmission failure if the frequency offset is greater than 1 GHz. Even in a gigabit-capable transceiver module, a higher precision wavelength locker is also needed to prevent channel crosstalk.

Tunable lasers used in DWDM systems mainly include Distributed Bragg Reflector (DBR) lasers, Distributed Feedback (DFB) lasers, External Cavity Lasers (ECL), and the like, where the ECL cost is high, the DFB lasers are simple, the DBR lasers cost is low, and currently, the DBR lasers are the mainstream technology of tunable lasers, and the DBR lasers are based on the principle that an optical signal oscillated from an active region passes through a Bragg ReflectorThe required wavelength is obtained after the grating is screened, a Digital mode Distributed Bragg Reflector (DS-DBR) laser can be controlled by addressing through a multi-electrode structure, a peak is selected from a sampling grating to serve as a lasing wavelength, and a phase region is responsible for fine adjustment. The structure is shown in figure 1, wherein the front grating and the rear grating reflection area are formed by chirped gratings and provide comb-shaped reflection peaks, large-scale wavelength shift of a C wave band can be realized by different combinations of the front grating and the rear grating, the active gain area provides optical gain in a resonant cavity, and the phase area can slightly tune the optical frequency in the resonant cavity. Wherein, I₁、I₂、I₃，I₄，I₅、I₆、I₇，I₈Indicating the control pin current, I, of the front grating reflection area_gIndicates the active gain region control pin current, I_pIndicating phase zone control pin current, I_rIndicating that the back grating reflective region controls the pin current.

The basic principle of the current wavelength locking scheme is to convert the wavelength information of the optical signal into amplitude information so that the detection can be performed using a photodiode. The key device that converts the wavelength information of the optical signal into amplitude information is referred to herein as a wavelength locker. The wavelength locker converts the wavelength information of the optical signal into a current signal to be output, the external circuit converts the current signal output by the external circuit into a voltage signal to be monitored, and the parameters of the laser, such as temperature, voltage and the like, are controlled according to the detection data, so that the wavelength of the optical signal output by the laser is controlled, and the purpose of stably outputting the wavelength is achieved.

The conventional wavelength locker comprises an interference filter and a Fabry-Perot etalon (F-P etalon), wherein the interference filter can only be used for a certain specific wavelength, and the F-P etalon is a general optical device and consists of a pair of flat glass plated with a reflecting film and parallel spacing components, and the F-P etalon is basically not influenced by temperature and other circuits after being packaged, so that the accuracy of detection information is favorably maintained.

When a light beam is irradiated on the F-P etalon, a reflection signal and a refraction signal are generated, and the light beam is between two planes of the F-P etalonBack and forth reflection and gradual transmission, light intensity of transmitted light I_tAnd the intensity of incident light I_iThe relationship between them is shown as follows:

wherein n is the refractive index of the plate glass in the F-P etalon, l is the thickness of the plate glass, lambda is the wavelength of incident light, theta is the incident angle of the light beam, the light beam formed by superposing a plurality of reflected light signals is converted into current by the photodiode, the light beam formed by superposing a plurality of transmitted light signals is converted into current by the photodiode, I_t/I_iVarying with the wavelength of the incident light, a comb filter is formed as shown in FIG. 2, where i_E1Is a current formed by transmitted light i_E2Is the current formed by the reflected light, I_EThe peak and the trough of the two comb filters are symmetrical with each other, the period between the peaks is called Free Spectral Range (FSR), wherein FSR is c/(2 nlcs θ), where c is the speed of light, n is the refractive index of the plate glass in the F-P etalon, l is the thickness of the plate glass, θ is the incident angle of the light beam, and the shape of the comb filters is represented by the sharpness formula: r is the reflectivity of the flat glass in the F-P etalon, and the shape of the comb filter is steeper when F is larger.

As can be seen from fig. 2, the light beam formed by superimposing the light signals reflected by the incident light beam is converted into a current i by a photodiode_E2The light beam formed by superposing the light signals transmitted by the incident light beam is converted into a current i by another photodiode_E1The ratio of the two currents is related to the wavelength of the incident light, and the change of the wavelength of the incident light can be judged by the change of the ratio or the difference of the two currents. Also, as can be seen from FIG. 2, at i_E1Point m at which the slope is maximum_EvIn the vicinity, the current change reflected by the wavelength change is the largest and can be considered as linear.

When the laser leaves a factory, four current values corresponding to different wavelengths are stored in a mode of pre-establishing a lookup table and are used for tuning the wavelength of an International Telecommunication Union (ITU). For example, in a 50GHz spaced WDM system, the FSR is determined by the refractive index of the plate glass in an F-P etalonIt was determined that the period of the F-P etalon could be designed to be equal to 50GHz, and the i-in the transfer function of the F-P etalon (i.e., the curve shown in FIG. 2)_E1Curve of (a) and (i)_E2The intersection point of the curves of (i.e. i)_E1The point of maximum slope in the curve) is aligned with the center wavelength of the ITU wavelength table, the wavelength of the light output by the laser at the time of factory shipment is the ITU wavelength point, the DSP system records the current value passing through the F-P etalon at that time, and as the wavelength of the light output by the laser shifts as time elapses, the change in the current value can be detected when the light beam passes through the F-P etalon, and at this time, the linear change in the wavelength can be generated by linearly adjusting the pin current of the DS-DBR laser, so that the detected current linearly changes back to the current recorded at the time of factory shipment.

However, when the wavelength drift exceeds the transfer function of the F-P etalon by more than one period, the periodicity of the transfer function of the F-P etalon may result in failure to detect the correct frequency shift. In addition, since the F-P etalon has different slopes at various points in its transfer function, as shown in fig. 2, the region A1 between the peak and the trough is a linear region, the region A2 near the peak top is a non-linear region, when the wavelength shift falls in the a2 region, the current value change corresponding to the same frequency shift will be smaller than in the linear region, this results in a poor accuracy of measuring the frequency offset, whereas the electrical signal of a given system always has a maximum and a minimum range, even if an amplifier is followed to linearly amplify the change in current when the frequency is shifted to the a2 region, this is likely due to the fact that the current changes by a value outside a reasonable range such as the ADC input voltage range when the frequency shifts to the a1 region, therefore, the locking accuracy of the current wavelength locking scheme is limited by the size of the frequency offset value, and cannot achieve high accuracy in the full-band range.

In summary, the current wavelength locking scheme cannot detect the correct frequency offset when the wavelength drift exceeds one period of the transmission function of the F-P etalon; and the locking precision of the current wavelength locking scheme is limited by the size of the frequency offset value, and the high precision in the full-wave band range cannot be realized.

Disclosure of Invention

The embodiment of the invention provides a wavelength locker, a wavelength locking method and a wavelength locking device, which are used for solving the problems that the correct frequency offset cannot be detected when the frequency drift exceeds one period of a transmission function of an F-P etalon, the locking precision is limited by the size of a frequency offset value, and the high precision in a full-waveband range cannot be realized in the conventional wavelength locking scheme.

In a first aspect, a wavelength locker is provided, comprising a coupler, a first fabry-perot F-P etalon, a second F-P etalon, and a detection processing circuit;

the coupler is used for dividing the received optical signal into two optical signals, and the optical signal received by the coupler is a beam of optical signal which is obtained by splitting the optical signal emitted by the laser;

the first F-P etalon is used for reflecting and refracting a beam of optical signals divided by the coupler; the difference between the maximum frequency and the minimum frequency of the linear area in one period of the transmission function of the first F-P etalon is not more than the required minimum detection precision;

the second F-P etalon is used for reflecting and refracting the other light signal divided by the coupler; the period length of the transmission function of the second F-P etalon is not less than twice the maximum value of the frequency offset of the laser; the frequency of an optical signal with a preset wavelength of the laser is located in a linear area of a transmission function of the first F-P etalon and is located in a linear area of a transmission function of the second F-P etalon;

the detection processing circuit is used for adjusting the pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon, and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that the frequency offset of the laser is within an error range.

With reference to the first aspect, in a first possible implementation manner, a period length of a transmission function of the second F-P etalon is a positive integer multiple of a period length of a transmission function of the first F-P etalon.

With reference to the first possible implementation manner of the first aspect, in a second possible implementation manner, if the transmission function of the second F-P etalon is a peak at the first frequency, the transmission function of the first F-P etalon is also a peak at the first frequency.

With reference to the first aspect, in a third possible implementation manner, a difference between a maximum frequency and a minimum frequency of a linear region within one period of a transfer function of the first F-P etalon is equal to a required minimum detection accuracy.

With reference to the first aspect, in a fourth possible implementation manner, the detection processing circuit is specifically configured to:

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value does not exceed a first threshold value;

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and the second pre-stored value does not exceed a second threshold value; when the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value does not exceed a second threshold value, the frequency offset of the laser is within an error range;

the first pre-stored value is a comparison result of an electric signal converted from an optical signal reflected by the second F-P etalon and an electric signal converted from a transmitted optical signal when the laser emits an optical signal with a preset wavelength; and the second pre-stored value is a comparison result of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.

With reference to the fourth possible implementation manner of the first aspect, in a fifth possible implementation manner, a comparison result of the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal is a difference value between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal;

and the first pre-stored value is the difference value between an electric signal converted from the optical signal reflected by the second F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.

With reference to the fourth possible implementation manner of the first aspect, in a sixth possible implementation manner, the comparison result of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal is a difference value between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal;

and the second pre-stored value is the difference value of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.

In a second aspect, a method for wavelength locking is provided, including:

acquiring an optical signal reflected by the first F-P etalon and a transmitted optical signal, and acquiring an optical signal reflected by the second F-P etalon and a transmitted optical signal;

adjusting the pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that the frequency offset of the laser is within an error range;

the first F-P etalon reflects and refracts a beam of optical signals divided by the coupler; the coupler is used for splitting one beam of optical signal emitted by the laser into two beams of optical signals after the optical signal is split; the difference between the maximum frequency and the minimum frequency of the linear area in one period of the transmission function of the first F-P etalon is not more than the required minimum detection precision; the second F-P etalon reflects and refracts the other light signal divided by the coupler; the period length of the transmission function of the second F-P etalon is not less than twice the maximum value of the frequency offset of the laser; the frequency of the optical signal of the preset wavelength of the laser is located in the linear area of the transmission function of the first F-P etalon and located in the linear area of the transmission function of the second F-P etalon.

With reference to the second aspect, in a first possible implementation manner, adjusting a pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon, and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon so that a frequency offset of the laser is within an error range specifically includes:

With reference to the first possible implementation manner of the second aspect, in a second possible implementation manner, a comparison result of the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal is a difference value between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal;

With reference to the first possible implementation manner of the second aspect, in a third possible implementation manner, a comparison result of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal is a difference value between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal;

With reference to the second aspect, in a fourth possible implementation manner, the period length of the transmission function of the second F-P etalon is a positive integer multiple of the period length of the transmission function of the first F-P etalon.

With reference to the fourth possible implementation manner of the second aspect, in a fifth possible implementation manner, if the transmission function of the second F-P etalon is a peak at the first frequency, the transmission function of the first F-P etalon is also a peak at the first frequency.

With reference to the second aspect, in a sixth possible implementation manner, a difference between a maximum frequency and a minimum frequency of a linear region within one period of a transmission function of the first F-P etalon is equal to a required minimum detection accuracy.

In a third aspect, a wavelength locker is provided, comprising:

the acquisition module is used for acquiring the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon and acquiring the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon;

the adjusting module is used for adjusting the pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that the frequency offset of the laser is within an error range;

the first F-P etalon reflects and refracts a beam of optical signals divided by the coupler; the coupler divides one beam of optical signal emitted by the laser into two beams of optical signals after the optical signal is split; the difference between the maximum frequency and the minimum frequency of the linear area in one period of the transmission function of the first F-P etalon is not more than the required minimum detection precision; the second F-P etalon reflects and refracts the other light signal divided by the coupler; the period length of the transmission function of the second F-P etalon is not less than twice the maximum value of the frequency offset of the laser; the frequency of the optical signal of the preset wavelength of the laser is located in the linear area of the transmission function of the first F-P etalon and located in the linear area of the transmission function of the second F-P etalon.

With reference to the third aspect, in a first possible implementation manner, the adjusting module is specifically configured to:

With reference to the first possible implementation manner of the third aspect, in a second possible implementation manner, a comparison result of the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal is a difference value between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal;

With reference to the first possible implementation manner of the third aspect, in a third possible implementation manner, a comparison result of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal is a difference value between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal;

The embodiment of the invention has the beneficial effects that:

according to the wavelength locker, the wavelength locking method and the wavelength locking device provided by the embodiment of the invention, because the period length of the transmission function of the second F-P etalon is not less than twice of the maximum value of the frequency deviation of the laser, the deviation of the wavelength of the optical signal emitted by the laser cannot exceed half of one period of the transmission function of the F-P etalon, even if the curve of each period of the transmission function of the F-P etalon is a symmetrical curve, when the frequency of the optical signal with the preset wavelength of the laser is located in the linear area of the transmission function of the second F-P etalon, the detection processing circuit can correctly detect the deviation of the wavelength of the optical signal emitted by the laser, so that the pin current of the laser is adjusted, and the wavelength of the optical signal emitted by the laser is close to the preset wavelength. After the detection processing circuit adjusts and adjusts the pin current of the laser according to the optical signal reflected by the second F-P etalon and the transmitted optical signal, so that the wavelength of the optical signal emitted by the laser is as close to the preset wavelength as possible, the frequency of the optical signal emitted by the laser is located in the linear region of the transmission function of the first F-P etalon at this time, and since the difference between the maximum frequency and the minimum frequency of the linear region in one period of the transmission function of the first F-P etalon is not greater than the required minimum detection precision, the detection processing circuit can measure the offset generated by the wavelength of the optical signal emitted by the laser with the minimum detection precision not greater than the required, thereby adjusting the pin current of the laser, and enabling the frequency offset of the laser to be within the error range. Therefore, after the first F-P etalon is combined with the second F-P etalon to be used, the detection processing circuit can realize high-precision detection and locking in the full-wave band range.

Drawings

FIG. 1 is a schematic diagram of a DS-DBR tunable laser in the prior art;

FIG. 2 is a graph of current converted by an optical signal transmitted by a prior art F-P etalon versus frequency of the optical signal and a graph of current converted by a reflected optical signal versus frequency of the optical signal;

FIG. 3 is a schematic structural diagram of a wavelength locker according to an embodiment of the present invention;

FIG. 4 is a second schematic structural diagram of a wavelength locker according to an embodiment of the present invention;

fig. 5 is a plot of the transfer function of a first F-P etalon and a plot of the transfer function of a second F-P etalon in a wavelength locker, according to embodiments of the present invention;

FIG. 6 is a flowchart of a wavelength locking method according to an embodiment of the present invention;

FIG. 7 is a second flowchart of a wavelength locking method according to an embodiment of the present invention;

FIG. 8 is a flowchart illustrating a wavelength locking method according to an embodiment of the present invention;

fig. 9 is a structural diagram of a wavelength locker according to an embodiment of the present invention.

Detailed Description

According to the wavelength locker, the wavelength locking method and the wavelength locking device provided by the embodiment of the invention, the second F-P etalon and the detection processing circuit realize correct detection of frequency offset, coarse adjustment of the wavelength of an optical signal emitted by the laser is realized, the first F-P etalon and the detection processing circuit realize high-precision detection of the frequency offset, and high-precision locking of the wavelength of the optical signal emitted by the laser is realized.

The following describes specific embodiments of a wavelength locker, a wavelength locking method and a wavelength locking device according to embodiments of the present invention with reference to the accompanying drawings.

The wavelength locker provided by the embodiment of the present invention, as shown in fig. 3, includes a coupler 31, a first fabry-perot F-P etalon 32, a second F-P etalon 33, and a detection processing circuit 34;

the coupler 31 is configured to divide the received optical signal into two optical signals, where the optical signal received by the coupler 31 is one optical signal obtained by splitting the optical signal emitted by the laser 35;

a first F-P etalon 32 for reflecting and refracting one of the optical signals split by the coupler 31; the difference between the maximum frequency and the minimum frequency of the linear region within one period of the transfer function of the first F-P etalon 32 is not more than the required minimum detection accuracy;

a second F-P etalon 33 for reflecting and refracting the other optical signal split by the coupler 31; the period length of the transfer function of the second F-P etalon 33 is not less than twice the maximum value of the frequency shift of the laser 35; the frequency of the optical signal of the preset wavelength of the laser 35 is located in the linear region of the transmission function of the first F-P etalon 32 and in the linear region of the transmission function of the second F-P etalon 33;

and a detection processing circuit 34 for adjusting the pin current of the laser 35 based on the optical signal reflected and transmitted by the first F-P etalon 32 and the optical signal reflected and transmitted by the second F-P etalon 33 so that the frequency shift of the laser 35 is within an error range.

Alternatively, in practical applications, the wavelength locker provided in the embodiment of the present invention may adopt the structure shown in fig. 4, wherein the detection processing circuit includes four photodiodes 41, four first transimpedance amplifiers 42, two subtractors 43, a proportional-integral-derivative (p.i.d) control unit, a Digital Signal Processing (DSP) unit 45, and four second transimpedance amplifiers 46.

The laser 35 output wavelength is λ₀With a power of P₀The voltage signal entering the PID control unit is:

V_E11(ν)＝α₁α₂P₀R_E11A₁₁T_E1(ν)；

V_E12(ν)＝α₁α₂P₀R_E12A₁₂(1-T_E1(ν))；

V_E21(ν)＝α₁α₂P₀R_E21A₂₁T_E2(ν)；

V_E22(ν)＝α₁α₂P₀R_E22A₂₂(1-T_E2(ν))；

wherein_，α₁α, which is the splitting ratio of a coupler that splits the optical signal emitted from the laser 35₂Is the splitting ratio, R, of the coupler 31_E11R_E12R_E21R_E22Is the responsivity of four photodiodes, A₁₁A₁₂A₂₁A₂₂Respectively, the amplification factor, T, of four transimpedance amplifiers_E1Is the transfer function, T, of a first F-P etalon_E2Is the transfer function of the second F-P etalon:

T_E1(ν)＝[1+F_E1sin²(πν/Δν_fine)]；

T_E2(ν)＝[1+F_E2sin²(πν/Δν_corase)]；

F_E1is the sharpness of the first F-P etalon, F_E2Is the sharpness, Δ ν, of a second F-P etalon_fineIs the FSR, Deltav, of a first F-P etalon_coraseIs the FSR of the second F-P etalon.

As can be seen from the expression of the signal entering the PID control unit, the current period corresponding to the reflected light signal and the current period corresponding to the transmitted light signal of the same F-P etalon are consistent, wherein the period of the transmission function of the first F-P etalon is Deltav_fineThe period of the transfer function of the second F-P etalon is Deltav_corase。

Because the period and the phase of the transmission function of the F-P etalon depend on the wavelength, the angle, the plate spacing and the reflectivity of the flat plate material of incident light, under the condition that the wavelength of the incident light of the first F-P etalon is the same as that of the incident light of the second F-P etalon and the angle of the incident light is the same, two F-P etalons with the period and the phase of the transmission function completely meeting the requirements can be designed by using materials with different plate spacing and different reflectivity.

Optionally, a period length of the transmission function of the second F-P etalon is a positive integer multiple of a period length of the transmission function of the first F-P etalon. Thus, when the laser is a tunable laser, the wavelength of each light signal which can be emitted and is set by the laser when the laser leaves a factory can be located in the linear area of the transmission function of the first F-P etalon and the linear area of the transmission function of the second etalon.

Optionally, if the transfer function of the second F-P etalon is a peak at the first frequency, the transfer function of the first F-P etalon is also a peak at the first frequency. That is, the position of the peak of the transmission function of the second F-P etalon overlaps the position of a part of the peak of the transmission function of the first F-P etalon, so that it is ensured that the frequency of the optical signal of the preset wavelength of the laser is located in the linear region of the transmission function of the first F-P etalon and in the linear region of the transmission function of the second F-P etalon.

Optionally, a difference between a maximum frequency and a minimum frequency of a linear region within one period of a transfer function of the first F-P etalon is equal to a required minimum detection accuracy.

Optionally, the detection processing circuit in the wavelength locker provided in the embodiment of the present invention is specifically configured to: adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value does not exceed a first threshold value;

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and the second pre-stored value does not exceed a second threshold value;

And when the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value is not more than a first threshold value, and the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and the second pre-stored value is not more than a second threshold value, the wavelength of the optical signal emitted by the laser is within an error range.

The comparison result of the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal may be a difference between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal, or a ratio of the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal. When the comparison result of the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal is the difference between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal, the first pre-stored value is the difference between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal when the laser outputs the optical signal with the set wavelength. When the comparison result of the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal is the ratio of the electrical signal converted from the optical signal reflected by the second F-P etalon to the electrical signal converted from the transmitted optical signal, the first pre-stored value is the ratio of the electrical signal converted from the optical signal reflected by the second F-P etalon to the electrical signal converted from the transmitted optical signal when the laser outputs the optical signal with the set wavelength.

The comparison result of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal may be the difference between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal, or the ratio of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal. When the comparison result of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal is the difference between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal, the second pre-stored value is the difference between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal when the laser outputs the optical signal with the set wavelength. When the comparison result of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal is the ratio of the electrical signal converted from the optical signal reflected by the first F-P etalon to the electrical signal converted from the transmitted optical signal, the second pre-stored value is the ratio of the electrical signal converted from the optical signal reflected by the first F-P etalon to the electrical signal converted from the transmitted optical signal when the laser outputs the optical signal with the set wavelength.

The preset wavelength is the wavelength of the optical signal emitted by the laser set at the factory, and the product of the wavelength of the optical signal emitted by the laser and the frequency of the optical signal is equal to the optical speed, so that when the frequency of the optical signal emitted by the laser is shifted, the wavelength of the optical signal emitted by the laser deviates from the preset wavelength. Because the transfer function of the first F-P etalon is different from that of the second F-P etalon, the currents converted by the optical signals after the same frequency shift is reflected and transmitted by different F-P etalons are different.

Assuming that the laser has a maximum value of frequency shift of 0.1THz and the required minimum detection accuracy is 0.02THz, two F-P etalons of the transfer function of the curve as shown in fig. 5 can be used to detect and lock the wavelength of the optical signal emitted by the laser. Assuming that the frequency corresponding to the preset wavelength is 192.1125THz (i.e. q1 point), when the wavelength locker is factory-checked, the voltage generated after the laser emits the optical signal of the wavelength (assuming that the laser does not have a frequency shift in the initial stage of the life cycle) through the first F-P etalon and the second F-P etalon is saved as Ve1 and Ve2 through instrument calibration, and the voltage value VR/VP/VG of the pin currently transmitted from the DSP to the laser controller is recorded.

If the wavelength of the optical signal emitted by the laser is shifted, and the frequency of the optical signal emitted by the laser is changed from 192.1125THz (i.e. point q 1) to 192.22THz (i.e. point P1), the detection processing circuit obtains the voltage VE2 after the wavelength is shifted from the optical signal transmitted and reflected by the second F-P etalon, and determines a point P1 uniquely on the second F-P etalon (solid line in fig. 5) according to the voltage VE2 after the wavelength is shifted and the voltage VE2 (i.e. first pre-stored value) of the optical signal transmitted and reflected by the second F-P etalon at a preset wavelength, and compares the difference between VE2 and VE2 to apply a coarse adjustment to the magnitude of the current applied to the tunable laser pin (ont/real) so that 2 VE2 is close to VE2, and when the difference between VE2 and VE2 is not more than a certain limit, the corresponding point q of the transmission gate 2 on the second F-P2 is equal to a point P2, the voltage of the wavelength at the point q2 on the transmission function (dotted line in fig. 5) of the first F-P etalon is VE1, after comparing VE1 with VE1 (i.e., a second pre-stored value) of the optical signal transmitted and reflected by the first F-P etalon at a preset wavelength, the magnitude of the current applied to the tunable laser pin can be finely adjusted, so that VE1 approaches VE1, and when the difference between VE1 and VE1 is adjusted to not exceed a certain threshold, it can be considered that the wavelength of the optical signal emitted by the laser is within an error range, that is, the wavelength locking is completed.

As shown in fig. 6, a wavelength locking method provided in an embodiment of the present invention includes:

s601, acquiring a light signal reflected by the first F-P etalon and a transmitted light signal, and acquiring a light signal reflected by the second F-P etalon and a transmitted light signal;

s602, adjusting the pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon, and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that the frequency offset of the laser is within an error range;

Optionally, in the wavelength locking method provided in the embodiment of the present invention, as shown in fig. 7, S602 specifically includes:

s701, adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and a first pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value does not exceed a first threshold value;

s702, adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and the second pre-stored value does not exceed a second threshold value; when the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value does not exceed a second threshold value, the frequency offset of the laser is within an error range;

In practice, the rough tuning (i.e., S701) may need to obtain the comparison result between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal more than once, compare the comparison result with the first pre-stored value, and adjust the pin current of the laser device so that the difference between the comparison result between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal and the first pre-stored value does not exceed the first threshold value; and fine tuning (S702) may also be performed more than once by obtaining a comparison of the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal, comparing the comparison with a second pre-stored value, and adjusting the pin current of the laser. In the course of coarse tuning and fine tuning, after the pin current of the laser is adjusted, the wavelength of the optical signal emitted by the laser may be located in the linear region of the F-P etalon or may be located in the non-linear region of the F-P etalon.

Optionally, a period length of the transmission function of the second F-P etalon is a positive integer multiple of a period length of the transmission function of the first F-P etalon.

Optionally, if the transfer function of the second F-P etalon is a peak at the first frequency, the transfer function of the first F-P etalon is also a peak at the first frequency.

Fig. 8 is a flowchart of a wavelength locking method applied in practice according to an embodiment of the present invention, including:

s801, acquiring a light signal reflected by the first F-P etalon and a transmitted light signal, and acquiring a light signal reflected by the second F-P etalon and a transmitted light signal;

s802, determining a comparison result of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal according to the optical signal reflected by the first F-P etalon and the transmitted optical signal, and determining a comparison result of an electric signal converted from the optical signal reflected by the second F-P etalon and an electric signal converted from the transmitted optical signal according to the optical signal reflected by the second F-P etalon and the transmitted optical signal;

s803, determining the direction (i.e. increasing or decreasing) and the magnitude of the adjustment of the laser pin current according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value, and the preset wavelength, and adjusting the laser pin current;

s804, judging whether the difference between the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal is smaller than a first pre-stored value or not, if so, executing S805; otherwise, executing S803;

s805, determining the direction (i.e. increasing or decreasing) and the magnitude of the adjustment of the laser pin current according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second prestored value, and the preset wavelength, and adjusting the laser pin current;

s806, judging whether the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value is smaller than a second threshold value, if so, executing S807, otherwise, executing S805;

s807, wavelength locking is completed, that is, the wavelength of the optical signal emitted by the laser is within the error range.

Based on the same inventive concept, embodiments of the present invention further provide a wavelength locking device, and since the principle of the problem solved by the device is similar to that of the wavelength locking method, the implementation of the device may refer to the implementation of the method, and repeated details are omitted.

As shown in fig. 9, a wavelength locking device provided in an embodiment of the present invention includes:

the obtaining module 91 is configured to obtain an optical signal reflected by the first F-P etalon and a transmitted optical signal, and obtain an optical signal reflected by the second F-P etalon and a transmitted optical signal;

an adjusting module 92, configured to adjust a pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon, and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that a frequency offset of the laser is within an error range;

Optionally, the adjusting module 92 is specifically configured to:

As will be appreciated by one skilled in the art, embodiments of the present invention may be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present invention is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all such alterations and modifications as fall within the scope of the invention.

It will be apparent to those skilled in the art that various modifications and variations can be made in the embodiments of the present invention without departing from the spirit or scope of the embodiments of the invention. Thus, if such modifications and variations of the embodiments of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to encompass such modifications and variations.

Claims

A wavelength locker is characterized by comprising a coupler, a first Fabry-Perot F-P etalon, a second F-P etalon and a detection processing circuit;

the coupler is used for dividing the received optical signal into two optical signals, and the optical signal received by the coupler is a beam of optical signal after the optical signal emitted by the laser is split;

the first F-P etalon is used for reflecting and refracting a beam of optical signals divided by the coupler; the difference between the maximum frequency and the minimum frequency of the linear area in one period of the transmission function of the first F-P etalon is not more than the required minimum detection precision;

the second F-P etalon is used for reflecting and refracting the other light signal divided by the coupler; the period length of the transmission function of the second F-P etalon is not less than twice the maximum value of the frequency offset of the laser; the frequency of an optical signal with a preset wavelength of the laser is located in a linear area of a transmission function of the first F-P etalon and is located in a linear area of a transmission function of the second F-P etalon;

the detection processing circuit is used for adjusting the pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon, and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that the frequency offset of the laser is within an error range.
The wavelength locker of claim 1 wherein the period length of the transmission function of the second F-P etalon is a positive integer multiple of the period length of the transmission function of the first F-P etalon.
The wavelength locker of claim 2 wherein if the transfer function of the second F-P etalon is peaked at the first frequency, then the transfer function of the first F-P etalon is also peaked at the first frequency.
The wavelength locker of claim 1 wherein the difference between the maximum frequency and the minimum frequency of the linear region within one period of the transfer function of the first F-P etalon equals a minimum required detection accuracy.
The wavelength locker of claim 1 wherein the detection processing circuit is specifically configured to:

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value does not exceed a first threshold value;

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and the second pre-stored value does not exceed a second threshold value; when the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value does not exceed a second threshold value, the frequency offset of the laser is within an error range;

the first pre-stored value is a comparison result of an electric signal converted from an optical signal reflected by the second F-P etalon and an electric signal converted from a transmitted optical signal when the laser emits an optical signal with a preset wavelength; and the second pre-stored value is a comparison result of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
The wavelength locker of claim 5 wherein the comparison of the electrical signal converted from the optical signal reflected by the second F-P etalon with the electrical signal converted from the transmitted optical signal is the difference between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal;

and the first pre-stored value is the difference value between an electric signal converted from the optical signal reflected by the second F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
The wavelength locker of claim 5 wherein the comparison of the electrical signal converted from the optical signal reflected by the first F-P etalon with the electrical signal converted from the transmitted optical signal is the difference between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal;

and the second pre-stored value is the difference value of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
A method of wavelength locking, comprising:

acquiring an optical signal reflected by the first F-P etalon and a transmitted optical signal, and acquiring an optical signal reflected by the second F-P etalon and a transmitted optical signal;

adjusting the pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that the frequency offset of the laser is within an error range;

the first F-P etalon reflects and refracts a beam of optical signals divided by the coupler; the coupler divides one beam of optical signal emitted by the laser into two beams of optical signals after the optical signal is split; the difference between the maximum frequency and the minimum frequency of the linear area in one period of the transmission function of the first F-P etalon is not more than the required minimum detection precision; the second F-P etalon reflects and refracts the other light signal divided by the coupler; the period length of the transmission function of the second F-P etalon is not less than twice the maximum value of the frequency offset of the laser; the frequency of the optical signal of the preset wavelength of the laser is located in the linear area of the transmission function of the first F-P etalon and located in the linear area of the transmission function of the second F-P etalon.
The method of claim 8, wherein adjusting the pin current of the laser based on the optical signal reflected and transmitted by the first F-P etalon and the optical signal reflected and transmitted by the second F-P etalon such that the frequency offset of the laser is within an error range, comprises:

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value does not exceed a first threshold value;

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and the second pre-stored value does not exceed a second threshold value; when the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value does not exceed a second threshold value, the frequency offset of the laser is within an error range;

the first pre-stored value is a comparison result of an electric signal converted from an optical signal reflected by the second F-P etalon and an electric signal converted from a transmitted optical signal when the laser emits an optical signal with a preset wavelength; and the second pre-stored value is a comparison result of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
The method of claim 9, wherein the comparison of the electrical signal converted from the optical signal reflected by the second F-P etalon with the electrical signal converted from the transmitted optical signal is a difference between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal;

and the first pre-stored value is the difference value between an electric signal converted from the optical signal reflected by the second F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
The method of claim 9, wherein the comparison of the electrical signal converted from the optical signal reflected by the first F-P etalon with the electrical signal converted from the transmitted optical signal is a difference between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal;

and the second pre-stored value is the difference value of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
The method of claim 8, wherein the period length of the transmission function of the second F-P etalon is a positive integer multiple of the period length of the transmission function of the first F-P etalon.
The method of claim 12, wherein if the transfer function of the second F-P etalon is a peak at a first frequency, then the transfer function of the first F-P etalon is also a peak at the first frequency.
The method of claim 8, wherein a difference between a maximum frequency and a minimum frequency of a linear region within one period of a transfer function of the first F-P etalon is equal to a required minimum detection accuracy.
A wavelength locker, comprising:

the acquisition module is used for acquiring the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon and acquiring the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon;

the adjusting module is used for adjusting the pin current of the laser according to the optical signal reflected by the first F-P etalon and the optical signal transmitted by the first F-P etalon and the optical signal reflected by the second F-P etalon and the optical signal transmitted by the second F-P etalon, so that the frequency offset of the laser is within an error range;

the first F-P etalon reflects and refracts a beam of optical signals divided by the coupler; the coupler is used for splitting one beam of optical signal emitted by the laser into two beams of optical signals after the optical signal is split; the difference between the maximum frequency and the minimum frequency of the linear area in one period of the transmission function of the first F-P etalon is not more than the required minimum detection precision; the second F-P etalon reflects and refracts the other light signal divided by the coupler; the period length of the transmission function of the second F-P etalon is not less than twice the maximum value of the frequency offset of the laser; the frequency of the optical signal of the preset wavelength of the laser is located in the linear area of the transmission function of the first F-P etalon and located in the linear area of the transmission function of the second F-P etalon.
The apparatus of claim 15, wherein the adjustment module is specifically configured to:

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the second F-P etalon and the electric signal converted from the transmitted optical signal and the first pre-stored value does not exceed a first threshold value;

adjusting the pin current of the laser according to the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value and the set wavelength of the optical signal output by the laser, so that the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and the second pre-stored value does not exceed a second threshold value; when the difference between the comparison result of the electric signal converted from the optical signal reflected by the first F-P etalon and the electric signal converted from the transmitted optical signal and a second pre-stored value does not exceed a second threshold value, the frequency offset of the laser is within an error range;

the first pre-stored value is a comparison result of an electric signal converted from an optical signal reflected by the second F-P etalon and an electric signal converted from a transmitted optical signal when the laser emits an optical signal with a preset wavelength; and the second pre-stored value is a comparison result of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
The apparatus of claim 16, wherein the comparison of the electrical signal converted from the optical signal reflected by the second F-P etalon with the electrical signal converted from the transmitted optical signal is a difference between the electrical signal converted from the optical signal reflected by the second F-P etalon and the electrical signal converted from the transmitted optical signal;

and the first pre-stored value is the difference value between an electric signal converted from the optical signal reflected by the second F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.
The apparatus of claim 16, wherein the comparison of the electrical signal converted from the optical signal reflected by the first F-P etalon to the electrical signal converted from the transmitted optical signal is a difference between the electrical signal converted from the optical signal reflected by the first F-P etalon and the electrical signal converted from the transmitted optical signal;

and the second pre-stored value is the difference value of an electric signal converted from the optical signal reflected by the first F-P etalon and an electric signal converted from the transmitted optical signal when the laser emits the optical signal with the preset wavelength.