High-speed wavelength switching device and method based on the mode-hopping property of tunable lasers

Abstract

This invention discloses a high-speed wavelength switching device and method based on the mode-hopping property of tunable lasers, belonging to the fields of optical communication and laser technology. This invention utilizes the mode-hopping property of tunable lasers when there is a mode mismatch between the internal and external cavities to achieve high-speed switching. The device includes a tunable laser, a wavelength locking unit, a mode control unit, and a main control unit. The method establishes a mode-hopping mapping table through pre-calibration: traversing wavelength points and driving currents within the tunable range, and adjusting the piezoelectric ceramic voltage, the wavelength, current, and voltage data before and after mode hopping are recorded; during actual switching, the mode-hopping induction conditions are obtained by looking up the table according to the target wavelength, and a nanosecond-level current pulse sequence is injected to actively trigger mode hopping, with the wavelength locking unit completing wavelength locking and error verification. This invention transforms the harmful mode-hopping phenomenon into a controllable high-speed switching method, achieving switching speeds on the nanosecond scale. It has advantages such as low cost, good stability, and mass production capability, and can be widely applied in fields such as high-speed optical communication.

Description

Technical Field

[0001] This invention belongs to the field of optical communication and laser technology, and specifically relates to a high-speed wavelength switching device and method based on the mode-hopping characteristics of a tunable laser. Background Technology

[0002] In data centers or backbone networks, data packets are often routed using different center wavelengths. High-speed wavelength switching (wavelength switching time on the order of nanoseconds) allows tunable lasers to quickly "color" different data packets onto different operating wavelengths. Compared to traditional electrical switching, optical layer switching offers significant advantages in terms of efficiency and lower energy consumption. In passive optical networks such as 5G fronthaul and XG-PON, high-speed wavelength switching can rapidly achieve dynamic wavelength allocation based on real-time user feedback, greatly improving network resource utilization and fairness. In fields such as industrial process control or medical breath analysis, different gas molecules have unique absorption lines at different wavelengths. Rapid switching of the output wavelength across multiple characteristic absorption peaks of the target gas allows for real-time, highly sensitive detection of multi-component gases. Furthermore, high-speed wavelength switching can be used to test the response time and crosstalk of high-speed optical switches, and to simulate network transient effects caused by high-speed switching.

[0003] The main technical solutions for achieving rapid wavelength switching currently include the following: (1) Acousto-optic tunable filter method: Its core principle is to use the grating diffraction formed by ultrasonic waves in the crystal to achieve the screening and switching of specific wavelengths. This scheme usually has a switching time on the order of microseconds, the switching speed between waves is slow, the insertion loss of the device itself is as high as 4dB to 6dB, and the insertion loss is significantly correlated with the wavelength, which makes it difficult to guarantee the power stability after wavelength switching.

[0004] (2) Wavelength selective switching method: Its core principle is to control the angle deflection of the beam in space through liquid crystal or silicon-based optoelectronic technology to achieve dynamic routing of the desired wavelength. This scheme usually has a switching time in the millisecond range. Although the wavelength switching speed is improved, its cost is extremely high, and the number of ports (the number of wavelengths that can be switched) is strictly limited by the physical space of the optical system.

[0005] (3) Micro-ring modulator and photonic integration: Its core principle is to change the resonant wavelength of the micro-ring resonant cavity through thermo-optic or electro-optic effects to realize the switching and modulation of on-chip light. The switching time of this scheme can reach the nanosecond level, but small fluctuations in ambient temperature or the heating of the device itself may cause wavelength lock-up; at the same time, low yield and narrow tunable output range also limit its engineering application.

[0006] (4) Traditional tunable laser method: Its core principle is to change the optical length of the laser resonator cavity by changing the current, temperature or internal mechanical structure to achieve continuous switching between modes. This method usually has a switching time on the order of milliseconds, which is difficult to meet the industrial application requirements of data centers, 5G fronthaul and other fields. In addition, the traditional method also requires the development of complex mode hopping suppression schemes to achieve stable mode switching.

[0007] In summary, existing technologies suffer from slow switching speeds, high costs, poor stability, and narrow tunable ranges. Of particular note is that in the field of traditional tunable lasers, mode hopping has always been considered a non-ideal phenomenon that needs to be suppressed. Existing literature primarily focuses on the detection and suppression of mode hopping, and there are no reports on using actively induced mode hopping to achieve high-speed wavelength switching. Summary of the Invention

[0008] This invention aims to overcome the shortcomings of the prior art by actively utilizing the mode-hopping characteristics of tunable lasers to provide a high-speed wavelength switching device and method based on the mode-hopping characteristics of tunable lasers, thus solving the problems of slow switching speed and high cost caused by suppressing mode hopping in the prior art.

[0009] To achieve the above objectives, the present invention adopts the following technical solution: A high-speed wavelength switching device based on the mode-hopping characteristics of a tunable laser includes: A tunable laser for generating a wide-range, mode-skipping-free reference output optical signal, featuring a drive current input and a piezoelectric ceramic voltage control. A wavelength locking unit, whose input is connected to the output of a tunable laser, is used for identifying the output wavelength of the tunable laser and for quickly locking the output wavelength after actively inducing mode hopping. The mode control unit is connected to the drive current input terminals of the wavelength locking unit and the tunable laser, respectively. It is used to receive the wavelength information identified by the wavelength locking unit and generate a drive current pulse sequence for actively inducing mode hopping. The main control unit is connected to the piezoelectric ceramic voltage control terminal and the mode control unit of the tunable laser, respectively. It is used to send piezoelectric ceramic voltage control commands to the tunable laser and to send trigger commands for the drive current pulse sequence to the mode control unit.

[0010] Preferably, the wavelength locking unit is a wavelength locking device based on the Fabry-Perot etalon.

[0011] Preferably, the tunable laser is an external cavity tunable laser controlled by a combination of current and piezoelectric ceramics.

[0012] Furthermore, this invention also mentions a high-speed wavelength switching method based on the mode-hopping characteristics of a tunable laser. This method employs the high-speed wavelength switching device based on the mode-hopping characteristics of a tunable laser as described above, and specifically includes the following steps: Step S1: Set the operating parameters of the tunable laser through the main control unit, including the drive current and the cavity temperature balancing current, and preheat it to a stable state; Step S2: The main control unit sets the tunable laser to output a series of wavelength points in the tunable output range with tuning steps, and stays at each wavelength point for a preset time; Step S3: The main control unit sets the driving current of the tunable laser to traverse the preset range in steps, and at the same time, the wavelength locking unit collects the output wavelength value corresponding to each driving current at the current wavelength point. Step S4: Calculate the output wavelength difference under adjacent traversal currents through the mode control unit, and determine whether there is a point greater than the mode hopping judgment threshold. If there is, record the corresponding output wavelength and current value. Otherwise, apply a step offset voltage to the piezoelectric ceramic in the tunable laser and repeat the traversal and judgment process until mode hopping is induced. Step S5: Store the discrete data triplets corresponding to the mode hopping induced at different wavelengths as a preset mode hopping mapping table and write it into the main control unit; Step S6: Based on the target wavelength set by the user, query the corresponding piezoelectric ceramic voltage value and mode hopping induced current value from the preset mode hopping mapping table, and send them to the tunable laser and mode control unit; Step S7: The mode control unit injects a sequence of current pulses into the tunable laser to actively induce mode jumping and complete high-speed wavelength switching; Step S8: The wavelength locking unit locks the switched wavelength and determines whether the allowable error is met. If not, the enhancement pulse is re-injected until the target wavelength is locked.

[0013] Preferably, the driving current in step S1 is 400mA, the cavity temperature balancing current is 0.46A, and the preheating time is 10 minutes.

[0014] Preferably, the tunable output range in step S2 is [lam_min, lam_max], the tuning step is 1nm, and the dwell time at each wavelength point is 2s.

[0015] Preferably, the traversal interval of the driving current in step S3 is [I_min, I_max], where I_min = I_set - I_th, I_set is the normal operating driving current, I_th is the threshold current, and the traversal step size is 2mA.

[0016] Preferably, the mode skipping determination threshold in step S4 is the mode interval, which is 20pm; and the step offset voltage is 5V.

[0017] Preferably, the discrete data triplet in step S5 includes: the output wavelength before mode hopping, the output wavelength after mode hopping, and the corresponding piezoelectric ceramic voltage value.

[0018] Preferably, the current pulse sequence in step S7 is [I_kk, I_kk + I_Thresho, I_kk+1], where I_kk and I_kk+1 are mode-hopping induced current values, I_Thresho is an electrical pulse for rapidly induced mode jumping, the duration of the electrical pulse is 2ns, the amplitude is 0.8×K×(I_kk+1 -I_kk), and the multiplier K is 2; if the allowable error is not met in step S8, the multiplier K is increased by 1, and the active induced pulse is re-injected until the lock is successful.

[0019] The beneficial technical effects of this invention are as follows: 1. Fast switching speed: This invention breaks through the bottleneck of mechanical response speed (millisecond level) that limits the continuous tuning of traditional tunable lasers. By actively inducing mode jumping and utilizing the intrinsic high-speed jumping characteristics when the internal and external cavity modes are mismatched, combined with nanosecond-level electrical pulse injection, a wavelength switching speed on the order of nanoseconds is achieved, which can meet the stringent requirements of high-speed optical switching in data centers, 5G fronthaul and other applications.

[0020] 2. Low cost and easy to mass-produce: This invention is based on mature tunable laser products, without the need for complex optical systems or high-cost wavelength selection switches. High-speed switching is achieved through pre-calibration and electronic control. The process is mature and can be mass-produced.

[0021] 3. Novel technical approach: This invention overcomes the technical bias of simply suppressing mode hopping in traditional technology, and for the first time proposes to actively utilize the mode hopping characteristics of tunable lasers to achieve high-speed wavelength switching, transforming the originally undesirable negative phenomenon into an advantageous means of high-speed switching.

[0022] 4. High switching accuracy and good stability: The mode hopping induction conditions at each wavelength point are accurately recorded by a preset mode hopping mapping table. Combined with the closed-loop verification and adaptive pulse amplitude adjustment of the wavelength locking unit, the accuracy and long-term stability of wavelength switching are guaranteed.

[0023] 5. Wide range of applications: This invention can be extended to other types of tunable laser source products, providing advanced testing instruments for fields such as intelligent high-speed coherent network reconfigurable transmission, high-precision gas spectroscopy measurement and quantum key distribution, while further expanding the application scope of tunable lasers. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a typical high-speed wavelength switching device based on the mode-hopping characteristics of a tunable laser according to the present invention. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: This invention proposes a high-speed wavelength switching device and method based on the mode-hopping characteristics of tunable lasers. The core idea is to fully utilize the high-speed mode switching characteristics when the internal and external cavities of a tunable laser are mismatched, and actively induce controllable mode hopping (mode jumping) within the tunable range through the coordinated control of the driving current and the piezoelectric ceramic displacement (driving voltage), thereby achieving nanosecond-level high-speed wavelength switching.

[0026] Example 1: Device construction.

[0027] like Figure 1 As shown, the high-speed wavelength switching device in this embodiment includes: A tunable laser is used to generate a wide-range, mode-free reference output optical signal. In this embodiment, the tunable laser (1) is preferably an external cavity tunable laser controlled by a combination of current and piezoelectric ceramics.

[0028] The mode control unit is connected to the drive current input terminals of the wavelength locking unit and the tunable laser, respectively. It is used to receive the wavelength information identified by the wavelength locking unit and generate a drive signal sequence (i.e., drive current pulse sequence) for actively inducing mode hopping.

[0029] A wavelength locking unit, whose input is connected to the output of a tunable laser, is used for identifying the output wavelength of the tunable laser and for rapidly locking the output wavelength after actively inducing mode hopping. In this embodiment, the wavelength locking unit adopts a wavelength locking scheme based on the Fabry-Perot etalon.

[0030] The main control unit is connected to the piezoelectric ceramic voltage control terminal and the mode control unit of the tunable laser, respectively. It is used to send piezoelectric ceramic voltage control commands to the tunable laser and to send trigger commands for the drive current pulse sequence to the mode control unit.

[0031] Example 2: High-speed wavelength switching method.

[0032] Based on Embodiment 1 above, this embodiment provides a high-speed wavelength switching method based on the mode-hopping characteristics of a tunable laser, specifically including the following steps: Step 101: Initialize preheating; The main control unit programmatically loads the drive current I_set (400mA in this embodiment) required for the normal operation of the tunable laser, the operating current I_tec (0.46A in this embodiment) required for cavity temperature balance, and preheats the laser to T_warm (10 minutes in this embodiment) to bring it to a stable operating state.

[0033] Step 102: Set the wavelength point sequence; The main control unit sets the tunable laser within the tunable output range of [lam_min, lam_max] and outputs a series of wavelength points lam_i (i=1, 2, ..., M) with a tuning step delam (1nm in this embodiment). The dwell time of each wavelength point lam_i is T1 (2 seconds in this embodiment). Steps 103-104: Drive current traversal and wavelength acquisition; The main control unit sets the driving current of the tunable laser in the range of [I_min, I_max], and iterates through a series of current values ​​I_j (j=1, 2, ..., N) with a step size deltI (2mA in this embodiment), where I_min=I_set-I_th, I_th is the threshold current (20mA in this embodiment), and I_set=(I_max+I_min) / 2; The wavelength locking unit acquires the output wavelength value lam_out(lam_1, I_j) corresponding to each driving current I_j under the current wavelength point set lam_1. Steps 105-106: Model skipping determination; The mode control unit reads the wavelength value lam_out(lam_1, I_j) recorded by the wavelength locking unit and calculates the output wavelength difference dl_out(k) under adjacent traversal currents, where k=1,2,…,N-1; Determine whether there is a point in the one-dimensional array dl_out(k) that is greater than the mode hopping determination threshold lam_th (mode interval, which is 20pm in this embodiment). If it exists, it is determined that mode hopping has occurred, and proceed to step 107; if it does not exist, proceed to step 108. Step 107: Record the model skipping data (model skipping has occurred) The mode control unit records the two wavelength values ​​lam_out(lam_1, I_k) and lam_out(lam_1, I_k+1) corresponding to dl_out(k) at this time, and synchronously records the two corresponding current values ​​[I_k, I_k+1], and then proceeds to step 110.

[0034] Steps 108-109: Adjust the piezoelectric ceramic voltage and re-traverse (mode skipping did not occur); If no mode-hopping point is found in step 106, the main control unit reads the voltage value V_cu currently applied to the piezoelectric ceramic in the tunable laser, and then applies a step offset voltage V_pzt (5V in this embodiment) to the piezoelectric ceramic. After that, steps 103 to 107 are repeated until mode-hopping is induced.

[0035] Steps 110-111: Traverse all wavelength points and construct a mode-hopping mapping table; For the next wavelength point lam_i (i≥2), after a time of (i+1)×T1, the wavelength locking unit collects the output wavelength value lam_out(lam_i, I_j) corresponding to each driving current at that wavelength point. Repeat steps 103 to 109 to obtain the current pair that induces mode skipping and the corresponding piezoelectric ceramic voltage value at each wavelength point.

[0036] The discrete data triplets obtained at each wavelength point—the wavelength before mode hopping lam_out(lam_i, I_kk), the wavelength after mode hopping lam_out(lam_i, I_kk+1), and the corresponding piezoelectric ceramic voltage value V_cu1_jj—are stored as a preset mode hopping mapping table. Here, I_kk and I_kk+1 are the mode hopping induced current values, and jj and kk take values ​​of 1, 2, …, M, respectively.

[0037] Step 112: Write to the main control unit; The aforementioned preset mode-hopping mapping table is written into the main control unit's memory for subsequent high-speed switching.

[0038] Steps 113-115: Perform high-speed switching; According to the target wavelength lam_set set by the user, the main control unit queries the corresponding piezoelectric ceramic voltage value V_cu1_jj and mode hopping induced current value I_kk from the preset mode hopping mapping table, and sends V_cu1_jj to the piezoelectric ceramic of the tunable laser, and sends I_kk to the mode control unit.

[0039] The mode control unit injects a current pulse sequence into the tunable laser: [I_kk, I_kk + I_Thresho, I_kk+1]. Here, I_Thresho is a fast-inducing electrical pulse that triggers mode hopping, with a duration T_s on the order of nanoseconds (2ns in this embodiment), an amplitude of 0.8×K×(I_kk+1 - I_kk), and a multiplier K of 2 in this embodiment.

[0040] After a time interval T_s, the mode control unit injects a constant current value I_kk+1 into the tunable laser to maintain the output wavelength after switching, completes the high-speed inter-wave switching, and outputs the wavelength lam_final after wave cutting.

[0041] Steps 116-118: Locking and Verification; The wavelength locking unit locks the switched output wavelength lam_final and determines whether |lam_final - lam_set| is less than or equal to the wave-cutting allowable error d_lam (2pm in this embodiment).

[0042] If successful, the switch is complete, the output wavelength is stably locked to the target wavelength, and the process ends.

[0043] If this is not the case, then inject the active induced pulse back into the tunable laser and increase the multiplier K by 1 (i.e., K+1), repeating steps 115 to 118 until the output wavelength is locked to the target switching wavelength.

[0044] Currently, the main technical solutions for achieving rapid wavelength switching include: The acousto-optic tunable filter method, whose core principle is to use ultrasonic waves to form a grating diffraction within a crystal to achieve the selection and switching of specific wavelengths. The switching time is typically on the order of microseconds, the switching speed between waves is slow, and the insertion loss of the device itself is as high as 4dB to 6dB. Furthermore, the insertion loss is significantly correlated with the wavelength, making it difficult to guarantee power stability after wavelength switching. The wavelength selective switching method, whose core principle is to control the angle deflection of the beam in space through liquid crystal or silicon-based optoelectronic technology to achieve dynamic routing of the desired wavelength, typically has a switching time on the order of milliseconds. Although the switching speed is improved, its cost is extremely high, and the number of ports (wavelength switchability brush count) is strictly limited by the physical space of the optical system. The micro-ring modulator and photonic integration method, whose core principle is to change the resonant wavelength of a micro-ring resonant cavity through thermo-optic or electro-optic effects to achieve on-chip switching and modulation of light, typically has a switching time on the order of nanoseconds. Obviously, the wavelength switching speed of this scheme meets the above requirements, but slight fluctuations in ambient temperature or the heating of the device itself may cause wavelength lock-up. At the same time, yield rate and narrow tunable output range are also issues worth considering. Based on the tunable laser method, its core principle is to change the optical length of the laser resonator cavity by changing the current, temperature or internal mechanical structure to achieve continuous switching between modes (wavelengths). The switching time is usually on the order of milliseconds, which limits its industrial application in data centers, 5G fronthaul and other fields.

[0045] In view of this, this invention proposes a high-speed wavelength switching method based on the mode-hopping characteristic of tunable lasers. It fully utilizes the high-speed mode switching characteristic of tunable lasers when there is a mode mismatch between the internal and external cavities. Through the coordinated control of the driving current and the piezoelectric ceramic displacement (driving voltage), controllable mode hopping is induced within the tunable range, thereby achieving high-speed wavelength switching. This provides advanced testing instruments for fields such as intelligent high-speed coherent network reconfigurable transmission, high-precision gas spectroscopy measurement, and quantum key distribution. It also further expands the application scope of tunable lasers, increases application scenarios for tunable lasers, and promotes the rapid development of the tunable laser industry.

[0046] The key technical points are as follows: (1) Active utilization of mode switching of tunable laser: Based on the experimentally obtained preset mode switching mapping table, pulse sequence is used to actively induce mode switching, transforming the non-ideal state into a high-speed wavelength switching method, breaking through the limit of traditional tuning speed and reducing costs. (2) No complex feedback circuit is required. It makes full use of Siyi Technology’s existing mature products and achieves nanosecond-level high-speed wave cutting through pre-calibrated data. The process is mature and can be mass-produced. (3) It can be extended to other types of tunable laser source products.

[0047] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A high-speed wavelength switching device based on the mode-hopping characteristics of a tunable laser, characterized in that, include: A tunable laser for generating a wide-range, mode-skipping-free reference output optical signal, featuring a drive current input and a piezoelectric ceramic voltage control. A wavelength locking unit, whose input is connected to the output of a tunable laser, is used for identifying the output wavelength of the tunable laser and for quickly locking the output wavelength after actively inducing mode hopping. The mode control unit is connected to the drive current input terminals of the wavelength locking unit and the tunable laser, respectively. It is used to receive the wavelength information identified by the wavelength locking unit and generate a drive current pulse sequence for actively inducing mode hopping. The main control unit is connected to the piezoelectric ceramic voltage control terminal and the mode control unit of the tunable laser, respectively. It is used to send piezoelectric ceramic voltage control commands to the tunable laser and to send trigger commands for the drive current pulse sequence to the mode control unit.

2. The high-speed wavelength switching device based on the mode-hopping property of a tunable laser according to claim 1, characterized in that, The wavelength locking unit is a wavelength locking device based on the Fabry-Perot etalon.

3. The high-speed wavelength switching device based on the mode-hopping property of a tunable laser according to claim 1, characterized in that, The tunable laser is an external cavity tunable laser that uses the combined control of current and piezoelectric ceramics.

4. A high-speed wavelength switching method based on the mode-hopping characteristics of a tunable laser, characterized in that, The high-speed wavelength switching device based on the mode-hopping characteristics of a tunable laser as described in claim 1 specifically includes the following steps: Step S1: Set the operating parameters of the tunable laser through the main control unit, including the drive current and the cavity temperature balancing current, and preheat it to a stable state; Step S2: The main control unit sets the tunable laser to output a series of wavelength points in the tunable output range with tuning steps, and stays at each wavelength point for a preset time; Step S3: The main control unit sets the driving current of the tunable laser to traverse the preset range in steps, and at the same time, the wavelength locking unit collects the output wavelength value corresponding to each driving current at the current wavelength point. Step S4: Calculate the output wavelength difference under adjacent traversal currents through the mode control unit, and determine whether there is a point greater than the mode hopping judgment threshold. If there is, record the corresponding output wavelength and current value. Otherwise, apply a step offset voltage to the piezoelectric ceramic in the tunable laser and repeat the traversal and judgment process until mode hopping is induced. Step S5: Store the discrete data triplets corresponding to the mode hopping induced at different wavelengths as a preset mode hopping mapping table and write it into the main control unit; Step S6: Based on the target wavelength set by the user, query the corresponding piezoelectric ceramic voltage value and mode hopping induced current value from the preset mode hopping mapping table, and send them to the tunable laser and mode control unit; Step S7: The mode control unit injects a sequence of current pulses into the tunable laser to actively induce mode jumping and complete high-speed wavelength switching; Step S8: The wavelength locking unit locks the switched wavelength and determines whether the allowable error is met. If not, the enhancement pulse is re-injected until the target wavelength is locked.

5. The high-speed wavelength switching method based on the mode-hopping property of a tunable laser according to claim 4, characterized in that, The driving current in step S1 is 400mA, the temperature balancing current in the cavity is 0.46A, and the preheating time is 10 minutes.

6. The high-speed wavelength switching method based on the mode-hopping property of a tunable laser according to claim 4, characterized in that, The tunable output range in step S2 is [lam_min, lam_max], the tuning step is 1nm, and the dwell time at each wavelength point is 2s.

7. The high-speed wavelength switching method based on the mode-hopping property of a tunable laser according to claim 4, characterized in that, The traversal interval of the driving current in step S3 is [I_min, I_max], where I_min = I_set - I_th, I_set is the normal operating driving current, I_th is the threshold current, and the traversal step size is 2mA.

8. The high-speed wavelength switching method based on the mode-hopping property of a tunable laser according to claim 4, characterized in that, The mode skipping determination threshold in step S4 is the mode interval, which is 20pm; the step offset voltage is 5V.

9. The high-speed wavelength switching method based on the mode-hopping property of a tunable laser according to claim 4, characterized in that, The discrete data triplet mentioned in step S5 includes: the output wavelength before mode hopping, the output wavelength after mode hopping, and the corresponding piezoelectric ceramic voltage value.

10. The high-speed wavelength switching method based on the mode-hopping property of a tunable laser according to claim 4, characterized in that, The current pulse sequence mentioned in step S7 is [I_kk, I_kk + I_Thresho, I_kk+1], where I_kk and I_kk+1 are the mode-hopping induced current values, I_Thresho is the electrical pulse for rapidly induced mode jumping, the duration of the electrical pulse is 2ns, the amplitude is 0.8×K×(I_kk+1 - I_kk), and the multiplier K is 2; if the allowable error is not met in step S8, the multiplier K is increased by 1, and the active induced pulse is re-injected until the lock is successful.

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