Detection circuit for key parameters of tunable laser

Abstract

The utility model relates to a detection circuit for key parameters of a tunable laser. The circuit mainly comprises an ITLA current source circuit, a three-wire RTD circuit and an MPD detection circuit. Wherein the ITLA current source circuit comprises a plurality of FM constant power control circuits, and each FM constant power control circuit is connected with a functional module in the ITLA through a flexible board so as to provide a constant current source; the three-wire type RTD circuit is connected to the ITLA chip through a flexible board, and an RTD resistor of the three-wire type RTD circuit is arranged on the ITLA chip so as to realize real-time temperature monitoring of the ITLA chip; the number of the MPD detection circuits is at least two, one MPD detection circuit is arranged at the tail end of the ITLA to monitor the output light power of a light source, and the other MPD detection circuit is arranged between two functional modules of the ITLA to serve as a harmonic component of a sampling circuit detection signal to lock the waveform of the signal. According to the utility model, the stability of electric signals in the ITLA can be ensured, high-precision temperature measurement is realized, and frequency modulation and frequency locking are realized.

Description

Technical Field

[0001] The utility model relates to the technical field of lasers, in particular to a detection circuit for key parameters of tunable lasers. Background Art

[0002] With the requirements of modern optical communication networks for lasers, the advantages of tunable lasers (Integratable Tunable Laser Assembly, abbreviated as: ITLA) in terms of channel number, power, line width and relative intensity noise (RIN) are destined to be more and more widely used in future optical communication networks. The main function of ITLA is to provide a stable and tunable wavelength for the laser, among which frequency and phase are important indicators of ITLA.

[0003] The factors affecting frequency and phase are mainly divided into: (1) long-period frequency jitter, which is reflected as the slow frequency drift and jitter caused by the laser being affected by various electrical signals and thermal signals; (2) short-period phase jitter, which is reflected as the intrinsic phase noise of the laser; (3) amplitude jitter, which is reflected as the RIN noise of the laser. Therefore, the closed-loop control of ITLA parameters such as power, temperature, and wavelength is the focus of our research in developing ITLA products.

[0004] Since the frequency and phase of the tunable ITLA laser are easily affected by electrical and thermal signals and cause failures, closed-loop control of key parameters such as the power, temperature and wavelength of the laser is essential.

[0005] First, the driving voltages used by ITLA chips designed with silicon photonics and III-V materials vary greatly, and the SPEC (specification) requirements for circuits are very wide, requiring us to consider compatibility with different voltages in circuit design, and placing great demands on miniaturization and power consumption. Figure 1As shown in the figure, there are many current source designs in ITLA, which are divided into the following categories according to their main functions: gain control, including semiconductor optical amplifier (Semi-conductor Optical Amplifier, abbreviated as: SOA), GAIN (gainer); phase control, including PHASE (phase control feedback device), front grating (FRONT GRATING), back grating (BACK GRATING). Different current sources have voltage differences (0~12V) and current differences (0~300mA). Designing a universal miniaturized constant current source circuit and power detection circuit is the direction that this field has been looking for. In fact, although we can use many integrated circuits (integrated circuit, abbreviated as: IC) or temporary digital-analog converters (InterimDigital-Analog Converter, abbreviated as: IDAC) to achieve constant current power control, the miniaturized structure such as NANO ITLA is limited by its small size and cannot fit too many IC chips into a small space. In summary, affected by the above factors, the existing power detection methods and circuits cannot meet the miniaturization and differentiation requirements in ITLA applications.

[0006] Secondly, during the operation of the laser, the wavelength is easily affected by many factors: lasers are extremely sensitive to temperature and generally have temperature monitoring functions. Temperature changes will cause temperature drift effects, which will have a negative impact on the stability of the temperature control circuit, and directly affect the phase noise and line width of the laser's low-frequency segment. Therefore, designing an excellent and reliable temperature sampling circuit has always been a hot topic in laser research. Traditional thermistor voltage divider detection is prone to error, and the detection accuracy is not enough to meet the temperature monitoring needs of ITLA.

[0007] Finally, if the wavelength of the laser drifts during operation, the wavelength needs to be detected in real time so that it can be corrected through frequency modulation and frequency locking. The traditional closed-loop control is achieved by introducing a small signal, low-frequency sine wave or square wave into the current source, and then amplifying and detecting part of the optical signal at the output end of the laser through the AC amplifier circuit. The back-end sampling circuit and control circuit realize the detection of the same frequency or doubled frequency electrical signal, and the same frequency or doubled frequency signal is adjusted to the minimum by controlling the wave-locking optical path to realize the closed-loop control of frequency locking. This method is complex to implement and requires a signal generator, a multi-stage AC amplifier circuit, a high-order analog bandpass filter, and a same frequency signal detector. The related circuit components are difficult to put into the laser in an ultra-small package.

[0008] In view of the above situation, how to overcome the defects of the prior art and solve the above technical problems is a difficult problem to be solved in this technical field. Utility Model Content

[0009] Aiming at the defects or improvement needs of the prior art. The utility model proposes a detection circuit for the key parameters of a tunable laser, which can realize the linear regulation of the current in each channel in ITLA through a miniaturized VI conversion circuit, that is, an FM constant power control circuit, and monitor the real-time power at the same time to obtain constant power control and monitoring, thereby ensuring the stability of the electrical signal in ITLA; secondly, through a three-wire sampling circuit of a resistance temperature detector (RTC), that is, a three-wire RTD circuit, high-precision temperature measurement is achieved; finally, a sampling circuit of an automatic bias control circuit is provided, that is, an MPD detection circuit, based on which a disturbance detection method can be used to achieve frequency modulation and frequency locking.

[0010] The utility model adopts the following technical solutions:

[0011] The utility model provides a detection circuit for key parameters of a tunable laser, comprising an ITLA current source circuit, a three-wire RTD circuit and an MPD detection circuit; wherein the ITLA current source circuit comprises a plurality of FM constant power control circuits, each of which is connected to a functional module inside the ITLA through a flexible board to provide a constant current source; the three-wire RTD circuit is connected to an ITLA chip through a flexible board, and an RTD resistor of the three-wire RTD circuit is arranged on the ITLA chip to realize real-time temperature monitoring of the ITLA chip; at least two MPD detection circuits are arranged, wherein one MPD detection circuit is arranged at the end of the ITLA to realize output optical power monitoring of the light source, and the other MPD detection circuit is arranged between two functional modules of the ITLA to detect the harmonic component of the signal as a sampling circuit to realize waveform locking of the signal.

[0012] In a specific embodiment, the functional modules inside the ITLA include a SOA module and a GAIN module of the gain control type, and a PHASE module, a FRONT GRATING module and a BACK GRATING module of the phase control type; wherein the modules are arranged in the order of the SOA module, the FRONT GRATING module, the GAIN module, the PHASE module and the BACK GRATING module.

[0013] In a specific embodiment, the MPD detection circuit includes a first MPD detection circuit and a second MPD detection circuit, wherein the first MPD detection circuit is arranged behind the BACK GRATING module, and the second MPD detection circuit is arranged between the PHASE module and the BACK GRATING module.

[0014] In a specific embodiment, the FM constant power control circuit includes a first operational amplifier U2A and a second operational amplifier U2B, the first input end of the first operational amplifier U2A is connected to a resistor R1, the second input end of the first operational amplifier U2A is connected to a resistor R3, the output end of the first operational amplifier U2A is connected to a resistor Riim and then connected to the first input end of the second operational amplifier U2B; a capacitor C1 is connected between the second input end of the first operational amplifier U2A and the output end of the first operational amplifier U2A, and a resistor R4 is connected between the second input end of the first operational amplifier U2A and the resistor Riim; a resistor R2 is connected between the first input end of the first operational amplifier U2A and the first input end of the second operational amplifier U2B; and the output end of the second operational amplifier U2B is connected to resistors R5 and R6.

[0015] In a specific implementation, the overall power consumption of the FM constant power control circuit is 50 mW.

[0016] In a specific embodiment, the three-wire RTD circuit includes an ADC and a first wire resistor R connected in parallel to the ADC. LEAD1 , the second wire resistance R LEAD2 , the third wire resistance R LEAD3 The first wire resistance R LEAD1 The wire is connected to a first current source IDAC1, and the second wire resistor R LEAD2 The wire is connected to a second current source IDAC2, and the third wire resistor R LEAD3 A reference resistor R is connected between the wire where the ADC is located and the ground wire of the ADC. REF .

[0017] In a specific embodiment, the reference resistor R REF The accuracy is less than 0.1%.

[0018] In a specific embodiment, the three-wire RTD circuit has a measured accuracy of 0.01°C.

[0019] In a specific embodiment, the MPD detection circuit includes a third operational amplifier U4A and a fourth operational amplifier U4B, the first input end of the third operational amplifier U4A is connected to the MPD_SIG end, the second input end of the third operational amplifier U4A is connected to the MPD_REF end, and the output end of the third operational amplifier U4A is connected to the MPD_DC_ADC end; a capacitor C13 and a wire resistor R17 are connected in parallel between the first input end of the third operational amplifier U4A and the output end of the third operational amplifier U4A; the first input end of the fourth operational amplifier U4B is connected to the output end of the third operational amplifier U4A, the second input end of the fourth operational amplifier U4B is connected to the MPD_REF end, and the output end of the fourth operational amplifier U4B is connected to the wire resistor R24 ​​and then connected to the MPD_AC_ADC end; a capacitor C18 and a wire resistor R22 are connected in parallel between the first input end of the fourth operational amplifier U4B and the output end of the fourth operational amplifier U4B.

[0020] In a specific implementation, the signal in the MPD detection circuit includes a DC signal and an AC signal, the second-order RC filter cutoff frequency of the DC signal is 61KHz and 88KHz; the first-order RC filter cutoff frequency of the AC signal is 27KHz.

[0021] Compared with the prior art, the beneficial effects of the utility model are: providing a detection circuit for the key parameters of a tunable laser, building a high-precision current source through an operational amplifier (operational amplifier is referred to as an op amp for short), which not only meets the current requirements of different channels, but also can meet the different power supply requirements of optical chips, and through real-time power detection and feedback adjustment, it is ensured that the ITLA frequency and phase are affected by the electrical signal to a minimum. In addition, the TEC backplane temperature of the laser is detected using a three-wire RTD, and the actual measurement accuracy can reach 0.01°C. Compared with the traditional thermistor voltage divider detection, the accuracy of the feedback loop data of the TEC temperature control is further calibrated. Finally, disturbance detection is also realized through a simple sampling circuit, and the position of the wavelength is effectively detected and adjusted. Compared with the traditional average optical power closed-loop control method, the locking accuracy is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present utility model, the following briefly introduces the drawings required for use in the embodiments of the present utility model. Obviously, the drawings described below are only some embodiments of the present utility model, and for ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work.

[0023] Figure 1An internal block diagram of ITLA provided for an embodiment of the utility model;

[0024] Figure 2 It is a circuit diagram of an ITLA current source provided by an embodiment of the utility model;

[0025] Figure 3 It is a schematic diagram of the relationship between the output swing amplitude and the output current of the operational amplifier provided in the embodiment of the utility model;

[0026] Figure 4 It is a three-wire RTD circuit diagram provided by an embodiment of the utility model;

[0027] Figure 5 It is a schematic diagram of the actual measurement results of the three-wire RTD provided by the embodiment of the utility model;

[0028] Figure 6 This is a MPD detection circuit diagram provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0030] In the description of the present invention, the indicated orientation or position relationship is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention rather than requiring the present invention to be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0031] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. The present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0032] The utility model provides a detection circuit for key parameters of a tunable laser, including an ITLA current source circuit, a three-wire RTD circuit and an MPD detection circuit; wherein the ITLA current source circuit includes a plurality of FM constant power control circuits, each of which is connected to a functional module inside the ITLA through a flexible board to provide a constant current source; the three-wire RTD circuit is connected to the ITLA chip through the flexible board, and the RTD resistor of the three-wire RTD circuit is arranged on the ITLA chip to realize real-time temperature monitoring of the ITLA chip; at least two MPD detection circuits are arranged, wherein one MPD detection circuit is arranged at the end of the ITLA to realize output optical power monitoring of the light source, and the other MPD detection circuit is arranged between the two functional modules of the ITLA, and is used as a sampling circuit to detect the harmonic component of the signal to realize waveform locking of the signal.

[0033] Through the above-mentioned methods, this embodiment solves three problems.

[0034] Problem 1: Mainstream microcontrollers (MCU) and ASICs only support transistor transistor logic (TTL) and complementary metal oxide semiconductor (CMOS) levels and cannot directly drive power integrated circuits (PIC) with an operating voltage greater than 5V. The ITLA current source circuit of this embodiment uses an operational amplifier to build a high-precision current source, which not only meets the current requirements of different channels, but also meets the different power supply requirements of optical chips. Through real-time power detection and feedback adjustment, it is ensured that the ITLA frequency and phase are affected by electrical signals to a minimum.

[0035] Solution to Problem 2: There are many types of temperature compensation circuits. This embodiment uses a three-wire resistance temperature detector (RTD), that is, a three-wire RTD circuit to detect the temperature of the backplane of the laser's semiconductor refrigerator (TEC), abandons the traditional thermistor voltage division detection, eliminates the error influence of the lead resistance, and the actual measurement accuracy can reach 0.01°C. Compared with the traditional thermistor voltage division detection, the accuracy of the feedback loop data of the TEC temperature control is further calibrated.

[0036] Solution to problem three: If the wavelength of the laser drifts during operation, it needs to be corrected in time through frequency modulation and locking. This embodiment realizes disturbance detection through a simple sampling circuit, namely the MPD detection circuit, which effectively detects the position of the wavelength and adjusts it. Compared with the traditional average optical power closed-loop control method, the locking accuracy is greatly improved. For the disturbance detection method, this method is similar to the automatic bias control in the transmitting end of the coherent optical module. By adding a perturbation signal of a specific frequency, when the peak values ​​of the center wavelength of the Bragg grating area (BG), the center wavelength of the standard tool ET and the center of the cavity membrane of the phase PH are aligned, the optical power of the laser output light is the largest, and the AC component is the smallest at this time. Figure 1 In the MPD shown, the harmonic component of the signal is detected to achieve waveform locking of the signal. Based on this principle, this embodiment proposes an MPD circuit design for simultaneous detection of a DC signal and a perturbation signal, and achieves wavelength locking of ITLA through an automatic bias control algorithm.

[0037] refer to Figure 1 As shown, in one implementation of this preferred embodiment, the functional modules inside the ITLA include a SOA module and a GAIN module of the gain control type, and a PHASE module, a FRONT GRATING module, and a BACK GRATING module of the phase control type; wherein the modules are arranged in the order of the SOA module, the FRONT GRATING module, the GAIN module, the PHASE module, and the BACK GRATING module. In addition, the MPD detection circuit includes a first MPD detection circuit and a second MPD detection circuit, wherein the first MPD detection circuit is arranged behind the BACK GRATING module, and the second MPD detection circuit is arranged between the PHASE module and the BACK GRATING module, and the second MPD detection circuit is not shown in the figure.

[0038] refer to Figure 2As shown, in one implementation of the preferred embodiment, the FM constant power control circuit includes a first operational amplifier U2A and a second operational amplifier U2B, the first input end of the first operational amplifier U2A is connected to a resistor R1, the second input end of the first operational amplifier U2A is connected to a resistor R3, the output end of the first operational amplifier U2A is connected to a resistor Riim and then connected to the first input end of the second operational amplifier U2B; a capacitor C1 is connected between the second input end of the first operational amplifier U2A and the output end of the first operational amplifier U2A, a resistor R4 is connected between the second input end of the first operational amplifier U2A and the resistor Riim; a resistor R2 is connected between the first input end of the first operational amplifier U2A and the first input end of the second operational amplifier U2B; the output end of the second operational amplifier U2B is connected to resistors R5 and R6. In one implementation, the overall power consumption of the FM constant power control circuit is 50mW. Figure 2 In the figure, VIN+ on the left represents the DAC voltage value sent by the DAC port of the MCU; FM at the bottom is connected to the load of ITLA and used as a current source. In addition, Figure 2 U2 is divided into three parts: A, B, and C. Among them, U2A and U2B are operational amplifier units, and U2C is the operational amplifier power supply unit.

[0039] refer to Figure 2 This embodiment provides a VI conversion circuit for ITLA laser, which also has a real-time power monitoring function. Its working principle is as follows.

[0040]

[0041]

[0042] The op amp works under deep negative feedback conditions, so the op amp satisfies virtual short and virtual open conditions.

[0043]

[0044] Therefore, the differential voltage is at both ends of Riim. Under the premise of Riim<<10K, the output current IO is approximately equal to the differential input voltage Vin+-Vin- divided by Riim. The derivation process is as follows:

[0045]

[0046]

[0047] In the selection of components for the constant current source circuit, the selected op amp must first meet the maximum operating voltage of the PIC chip and be an operational amplifier (OPA) with low noise, low bias current, low offset, and low power consumption, such as the TLV910 series. Secondly, the maximum current of the current source needs to pay attention to the relationship between the output voltage swing and the output current to avoid being unable to output a larger current when the load voltage is too large. Refer to Figure 3 If the current source demand of ITLA is further increased, the resistance ratio on the P and N terminals of the op amp can be adjusted proportionally (R1 / R2=R3 / R4) or the Riim resistance can be reduced. Note that the resistance matching ratio is very high, otherwise new errors will be introduced. Figure 2 As shown. When the output drive current capability of the OPA exceeds the limit, use an OPA with a larger output drive current, such as the MAX4233 series. This circuit can meet the needs of optical chip drivers with different operating voltages. When collecting the current source voltage Uadc, the resistor divider is used to adjust the voltage to the appropriate range for the analog-to-digital converter (ADC) sampling.

[0048] refer to Figure 4 As shown, in one implementation of this preferred embodiment, the three-wire RTD circuit includes an ADC and a first wire resistor R connected in parallel to the ADC. LEAD1 , the second wire resistance R LEAD2 , the third wire resistance R LEAD3 The first wire resistance R LEAD1 The wire is connected to a first current source IDAC1, and the second wire resistor R LEAD2 The wire is connected to a second current source IDAC2, and the third wire resistor R LEAD3 A reference resistor R is connected between the wire where the ADC is located and the ground wire of the ADC. REF In one embodiment, the reference resistor R REF The accuracy is less than 0.1%. In one embodiment, the three-wire RTD circuit has a measured accuracy of 0.01°C.

[0049] refer to Figure 4 As shown, the temperature sampling circuit is very critical in ITLA. The three-wire RTD circuit measurement provided in this embodiment can provide an excellent combination of high accuracy and good stability. Compared with the two-wire RTD measurement, the lead resistance error is eliminated, and compared with the four-wire RTD measurement, the cost and complexity are reduced. When we ignore the influence of the lead resistance RLEAD, we can deduce:

[0050] V RTD=IDAC1*R RTD (1)

[0051] V REF =IDAC1*R REF (2)

[0052] When the ADC works in bipolar differential mode, it can be deduced from formula (1) (2) that

[0053] R RTD = Code RTD *R REF / Code ADC _Fullscale (3)

[0054] Among them, Code RTD is the ADC code, Code ADC _Fullscale is the ADC full-scale code. It can be seen that the RTD measurement is not affected by the accuracy and drift of the current source excitation IDAC, but the accuracy of the reference resistor RREF must be improved (<0.1%), and RREF is required to have a low temperature drift characteristic.

[0055] When considering the lead resistance R LEAD When, for a single current source IDAC1, R LEAD1 Add an error to the measurement. By adding IDAC2, the error in the wire resistance is removed using the current source IDAC2. When the wire resistance and the second current source are added, the equation becomes:

[0056] Code RTD =Code ADC _Fullscale·[I IDAC1 ·(R RTD +R LEAD1 )–(I IDAC2 ·R LEAD2 )]

[0057] / [(I IDAC1 +I IDAC2 )·R REF ](4)

[0058] R LEAD1 With R LEAD2 When designing PCB routing, pseudo differential routing is used, and Polar simulation is used to keep the characteristic impedance equal (R LEAD1 =R LEAD2 ), and then use the MUX multiplexer to exchange IDAC1 and IDAC2 to measure twice in each channel and take the average, so that IDAC1 = IDAC2, then formula (4) can be simplified to:

[0059] CodeRTD = Code ADC _Fullscale * R RTD / (2*R REF ) (5)

[0060] From formula (5), we can see that R RTD The error of the lead resistance has been removed. In the ratiometric measurement RTD mentioned above, it is still difficult to achieve the high-precision performance specified by the ADC. It is necessary to design a reasonable analog front end according to the device manual and optimize it for high-precision measurement applications, which will not be elaborated in this embodiment.

[0061] refer to Figure 5 As shown, this embodiment builds an actual circuit to verify the three-wire RTD measurement and its closed-loop control mentioned above, and the figure shows the measured RTD resistance measurement data on ITLA. The data length is 30 seconds, the sampling rate is 49 times / second, and the RTD_AD value has a linear correspondence with the RTD resistance value. After the software PID algorithm is optimized, after turning on the semiconductor cooler TEC temperature control, the change value of RTD_AD within 30 seconds does not exceed 10 AD values, achieving the expected 0.01℃ measurement accuracy and temperature control effect.

[0062] refer to Figure 6As shown, in one implementation of the preferred embodiment, the MPD detection circuit includes a third operational amplifier U4A and a fourth operational amplifier U4B, the first input end of the third operational amplifier U4A is connected to the MPD_SIG end, the second input end of the third operational amplifier U4A is connected to the MPD_REF end, and the output end of the third operational amplifier U4A is connected to the MPD_DC_ADC end in sequence with the wire resistor R20 and the wire resistor R19; a capacitor C13 and a wire resistor R17 are connected in parallel between the first input end of the third operational amplifier U4A and the output end of the third operational amplifier U4A, a capacitor C14 is connected between the wire resistor R20 and the wire resistor R19 and then grounded, a capacitor C15 is connected between the wire resistor R19 and the MPD_DC_ADC end and then grounded; the fourth operational amplifier U4B The first input terminal is connected to the output terminal of the third operational amplifier U4A. Specifically, the first input terminal of the fourth operational amplifier U4B is connected to the wire resistor R23 and the capacitor C17 in sequence and then connected between the wire resistor R20 and the wire resistor R19. The second input terminal of the fourth operational amplifier U4B is connected to the MPD_REF terminal. The output terminal of the fourth operational amplifier U4B is connected to the wire resistor R24 ​​and then connected to the MPD_AC_ADC terminal. A capacitor C18 and a wire resistor R22 are connected in parallel between the first input terminal of the fourth operational amplifier U4B and the output terminal of the fourth operational amplifier U4B. A capacitor C20 is connected between the second input terminal of the fourth operational amplifier U4B and the MPD_REF terminal and then grounded. A capacitor C19 is connected between the output terminal of the fourth operational amplifier U4B and the MPD_AC_ADC terminal and then grounded. In one embodiment, the MPD detection circuit includes a DC signal and an AC signal. The cutoff frequency of the second-order RC filter of the DC signal is 61KHz and 88KHz, which can be understood as two RC filters in parallel. The second order is to ensure a better filter effect. The cutoff frequency of the first-order RC filter of the AC signal is 27KHz. In addition, Figure 6 In the figure, the MPD_SIG terminal is the signal acquisition terminal of the MPD; the MPD_REF terminal is the bias voltage terminal of the MPD; the MPD_DC_ADC terminal is the acquisition terminal of the DC component of the MPD; and the MPD_AC_ADC terminal is the acquisition terminal of the AC component of the MPD.

[0063] refer to Figure 6As shown, the MPD sampling circuit (MPD detection circuit) can be divided into a DC component and an AC component. The AC signal feedback cavity mode and the grating, standard joint filter spectrum alignment state; the DC signal feedback grating and standard alignment state, as well as the cavity mode and their alignment state. Through an MPD, the relevant detection and feedback of the wavelength in ITLA can be completed. Among them, the second-order RC filter cutoff frequency of the DC signal is 61KHz, 88KHz; the first-order RC filter cutoff frequency of the AC signal is 27KHz. According to experimental verification, the corresponding DC signal and scrambled signal can be detected. In this circuit, a miniaturized op amp with low noise, low bias voltage and bias current, and a signal bandwidth that meets the requirements is preferred, such as the AD8606 series. The bias voltage MPD_REF should not be too large, which will reduce the effective range of ADC sampling. If it is too small, the op amp cannot normally enter the negative feedback state when the MPD is abnormally positively biased, resulting in circuit abnormality. After the DC sampling circuit and the AC sampling circuit are sent to the ADC for collection, the wavelength of ITLA can be locked by controlling the corresponding constant current source circuit through the wave locking principle introduced above.

[0064] In summary, the utility model provides a detection circuit for the key parameters of a tunable laser. A high-precision current source is built through an operational amplifier, which not only meets the current requirements of different channels, but also can meet the different power supply requirements of optical chips. Through real-time power detection and feedback adjustment, it ensures that the ITLA frequency and phase are affected by the electrical signal to a minimum. In addition, a three-wire RTD is used to detect the TEC backplane temperature of the laser, and the actual measurement accuracy can reach 0.01°C. Compared with the traditional thermistor voltage divider detection, the accuracy of the feedback loop data of the TEC temperature control is further calibrated. Finally, disturbance detection is also realized through a simple sampling circuit, and the position of the wavelength is effectively detected and adjusted. Compared with the traditional average optical power closed-loop control method, the locking accuracy is greatly improved.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A detection circuit for key parameters of a tunable laser, characterized in that: It comprises an ITLA current source circuit, a three-wire RTD circuit and an MPD detection circuit; wherein the ITLA current source circuit comprises a plurality of FM constant power control circuits, each of which is connected to a functional module inside the ITLA through a flexible board to provide a constant current source; the three-wire RTD circuit is connected to the ITLA chip through the flexible board, and the RTD resistor of the three-wire RTD circuit is arranged on the ITLA chip to realize real-time temperature monitoring of the ITLA chip; at least two MPD detection circuits are arranged, wherein one MPD detection circuit is arranged at the end of the ITLA to realize output optical power monitoring of the light source, and the other MPD detection circuit is arranged between two functional modules of the ITLA to detect the harmonic component of the signal as a sampling circuit to realize waveform locking of the signal.

2. The detection circuit of key parameters of tunable laser according to claim 1, characterized in that: The functional modules inside the ITLA include a SOA module and a GAIN module of the gain control type, and a PHASE module, a FRONT GRATING module and a BACK GRATING module of the phase control type; wherein the modules are arranged in the order of the SOA module, the FRONT GRATING module, the GAIN module, the PHASE module and the BACK GRATING module.

3. The detection circuit of key parameters of tunable laser according to claim 2, characterized in that: The MPD detection circuit includes a first MPD detection circuit and a second MPD detection circuit, wherein the first MPD detection circuit is arranged behind the BACK GRATING module, and the second MPD detection circuit is arranged between the PHASE module and the BACKGRATING module.

4. The detection circuit of key parameters of a tunable laser according to claim 1, characterized in that: The FM constant power control circuit includes a first operational amplifier U2A and a second operational amplifier U2B, wherein the first input end of the first operational amplifier U2A is connected to a resistor R1, the second input end of the first operational amplifier U2A is connected to a resistor R3, the output end of the first operational amplifier U2A is connected to a resistor Riim and then connected to the first input end of the second operational amplifier U2B; a capacitor C1 is connected between the second input end of the first operational amplifier U2A and the output end of the first operational amplifier U2A, and a resistor R4 is connected between the second input end of the first operational amplifier U2A and the resistor Riim; a resistor R2 is connected between the first input end of the first operational amplifier U2A and the first input end of the second operational amplifier U2B; and the output end of the second operational amplifier U2B is connected to resistors R5 and R6.

5. The detection circuit of key parameters of tunable laser according to claim 4, characterized in that: The overall power consumption of the FM constant power control circuit is 50 mW.

6. The detection circuit of key parameters of tunable laser according to claim 1, characterized in that: The three-wire RTD circuit includes an ADC and a first wire resistor R connected in parallel to the ADC. LEAD1 , the second wire resistance R LEAD2 , the third wire resistance R LEAD3 The first wire resistance R LEAD1 The wire is connected to a first current source IDAC1, and the second wire resistor R LEAD2 The wire is connected to a second current source IDAC2, and the third wire resistor R LEAD3 A reference resistor R is connected between the wire where the ADC is located and the ground wire of the ADC. REF .

7. The detection circuit of key parameters of tunable laser according to claim 6, characterized in that: The reference resistor R REF The accuracy is less than 0.1%.

8. The detection circuit for key parameters of a tunable laser according to claim 6, characterized in that: The actual measurement accuracy of the three-wire RTD circuit reaches 0.01°C.

9. The detection circuit of key parameters of tunable laser according to claim 1, characterized in that: The MPD detection circuit includes a third operational amplifier U4A and a fourth operational amplifier U4B, wherein the first input terminal of the third operational amplifier U4A is connected to the MPD_SIG terminal, the second input terminal of the third operational amplifier U4A is connected to the MPD_REF terminal, and the output terminal of the third operational amplifier U4A is connected to the MPD_DC_ADC terminal; a capacitor C13 and a wire resistor R17 are connected in parallel between the first input terminal of the third operational amplifier U4A and the output terminal of the third operational amplifier U4A; the first input terminal of the fourth operational amplifier U4B is connected to the output terminal of the third operational amplifier U4A, the second input terminal of the fourth operational amplifier U4B is connected to the MPD_REF terminal, the output terminal of the fourth operational amplifier U4B is connected to the wire resistor R24 ​​and then connected to the MPD_AC_ADC terminal; a capacitor C18 and a wire resistor R22 are connected in parallel between the first input terminal of the fourth operational amplifier U4B and the output terminal of the fourth operational amplifier U4B.

10. The detection circuit for key parameters of a tunable laser according to any one of claims 1 to 9, characterized in that: The signals in the MPD detection circuit include a DC signal and an AC signal. The second-order RC filter cutoff frequency of the DC signal is 61 KHz and 88 KHz; the first-order RC filter cutoff frequency of the AC signal is 27 KHz.

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