Backlight monitoring circuit of optical module and optical module

Abstract

The application discloses a backlight monitoring circuit of an optical module and the optical module. The backlight monitoring circuit of the optical module comprises a digital diagnosis unit, a plurality of lasers and at least one backlight monitoring diode. The at least one backlight monitoring diode is used for simultaneously receiving backlights of the two lasers and generating photo-generated current. Each backlight monitoring diode is connected with an ADC pin of the digital diagnosis unit. The digital diagnosis unit is used for collecting the sum of the photo-generated current of the backlight monitoring diodes through the ADC pin. pd总 The application also discloses a method for monitoring the backlights of the lasers. pd总 The application judges whether the change of the collected sum of the photo-generated current of the backlight monitoring diodes exceeds a set fluctuation range. If not, it indicates that the state of each laser is normal. If yes, it indicates that the state of the laser is abnormal. The application can realize the monitoring of the optical power of the multiple lasers under the condition of occupying only one ADC pin of an MCU, can save the hardware resource occupation, can simplify the layout space of a PCB, and can reduce the number of PDs on an optical path.

Description

Technical Field

[0001] This invention belongs to the field of optical communication technology, specifically relating to a backlight monitoring circuit for an optical module and an optical module. Background Technology

[0002] In optical modules, it is typically necessary to monitor the laser's emission power to understand its operational status in real time. Taking a traditional 100G LR4 optical module as an example... Figure 1 As shown, a backlight monitoring photodiode (MPD) is placed on the backlight surface of four parallel lasers LD1, LD2, LD3, and LD4. When the MPD receives light, it generates a photocurrent, with the current path flowing from VCC to PD. n ->R n ->land, where n represents 1, 2, 3, 4 respectively, thus in R n A voltage MPD will be generated on it. n Then MPD n ADCs connected to the MCU respectively n This allows the PD to be acquired in real time through the MCU's ADC sampling function. n The magnitude of the current is used to control the laser LD. n Light emission monitoring.

[0003] Modern high-speed optical modules face significant internal space constraints, especially as module sizes shrink and MCU resources and PCB layout become increasingly limited. The aforementioned approach requires utilizing four ADC pins of the MCU, which is clearly wasteful. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art and provide a backlight monitoring circuit and optical module for an optical module. It can monitor the optical power of multiple lasers by occupying only one ADC pin of an MCU. It can save hardware resources, simplify the PCB layout space, and reduce the number of PDs in the optical path.

[0005] The technical scheme of the present application is implemented as follows: The present application discloses a backlight monitoring circuit of an optical module, which comprises a digital diagnosis unit and a plurality of lasers, and further comprises at least one backlight monitoring diode, the at least one backlight monitoring diode being used to simultaneously receive backlights of two lasers and generate photo-generated current, each backlight monitoring diode being connected with an ADC pin of the digital diagnosis unit, the digital diagnosis unit being used to collect the total photo-generated current of the backlight monitoring diode through an ADC pin, and calculate the variation of the total photo-generated current of the backlight monitoring diode according to the collected total photo-generated current of the backlight monitoring diode, and compare the collected variation of the total photo-generated current of the backlight monitoring diode with a set fluctuation range, and determine whether the laser of a channel is abnormal when the collected variation of the total photo-generated current of the backlight monitoring diode exceeds the set fluctuation range.

[0006] Further, when one backlight monitoring diode is used to simultaneously receive backlights of two lasers, the backlight monitoring diode and the corresponding two lasers are respectively located at three vertices of an isosceles triangle, wherein the two lasers correspond to two base angles of the isosceles triangle, the backlight monitoring diode corresponds to a top angle of the isosceles triangle, and the backlight monitoring diode corresponds to the backlight surfaces of the two lasers, so that the backlight monitoring diode can receive the backlights of the two lasers with equal intensity.

[0007] Further, the backlight monitoring circuit of the present application further comprises at least one sampling resistor, the sampling resistor corresponding to the backlight monitoring diode one by one, the anode of each backlight monitoring diode being connected with one end of the corresponding sampling resistor, and the other end of the sampling resistor being grounded; and each sampling resistor is connected with a capacitor in parallel.

[0008] Further, when the sampling resistors are a plurality of, the resistances of the plurality of sampling resistors are different from each other.

[0009] Preferably, R2=k*R1, and the same applies to the subsequent.

[0010] The cathodes of the plurality of backlight monitoring diodes are connected with the anode of a power supply.

[0011] Further, the anode of each backlight monitoring diode is connected with an ADC pin of the digital diagnosis unit, the cathode of each backlight monitoring diode is connected with one end of an inductor, and the other end of the inductor is connected with a power supply VCC.

[0012] Further, the digital diagnosis unit is an MCU with an ADC function.

[0013] Further, when the collected variation of the total photo-generated current of the backlight monitoring diode exceeds the set fluctuation range, the digital diagnosis unit determines that the laser of a channel is abnormal, otherwise, it is determined that the lasers of each channel are normal.

[0014] Further, when the variation of the total photo-generated current I pd总 of the back light monitoring diode exceeds a set fluctuation range, the digital diagnosis unit is configured to sequentially determine whether the laser of each channel is abnormal, find the abnormal channel, and determine whether the laser of the nth channel is abnormal, and the specific steps are as follows:

[0015] the bias current of the laser of the nth channel is I b1 , the bias current of the laser of the remaining channels is I b0 , the lasers of all channels emit light at the same time, and the digital diagnosis unit samples I pd总1 ;

[0016] the bias current of the laser of the nth channel is I b2 , the bias current of the laser of the remaining channels is I b0 , the lasers of all channels emit light at the same time, and the digital diagnosis unit samples I pd总2 ;

[0017] the change rate Kn' of Ipd of the nth channel is calculated as follows:

[0018]

[0019] The calculated Kn' is compared with a preset Kn, when the difference between Kn' and Kn is within a set allowable range, it is determined that the state of the laser of the nth channel is normal, otherwise, it is determined that the state of the laser of the nth channel is abnormal.

[0020] Further, the digital diagnosis unit is configured to determine the Kn corresponding to the nth channel, and the determination method of the Kn corresponding to the nth channel is as follows: only the nth channel is turned on, two bias currents are respectively given to the laser of the nth channel, only the laser of the nth channel emits light, the digital diagnosis unit samples two photo-generated current values corresponding to the two bias currents respectively, a linear function is fitted according to the bias current and the corresponding photo-generated current value, and the Kn corresponding to the nth channel is obtained.

[0021] Further, when it is determined that the state of the laser of the nth channel is abnormal, the digital diagnosis unit is configured to calculate the emission optical power Pn' of the laser of the channel and report the same, and the calculation formula of the emission optical power Pn' of the laser of the channel is as follows: wherein kn is the slope obtained when the optical power of the nth channel is calibrated, and Pn is the optical power of the nth channel when the optical module normally works.

[0022] The application further discloses an optical module adopting the back light monitoring circuit.

[0023] The present application has at least the following beneficial effects: the present application adopts the above scheme, and realizes monitoring of the optical power of multiple lasers by occupying only one ADC pin of an MCU, thereby saving hardware resource occupation and simplifying PCB layout space.

[0024] In the optical path, each backlight monitoring diode of the present application is located at three vertices of an isosceles triangle, wherein two lasers correspond to two base angles of the isosceles triangle, the backlight monitoring diode corresponds to the top angle of the isosceles triangle, and the backlight surface of the backlight monitoring diode corresponds to the two lasers, so that the backlight monitoring diode can receive the backlights of the two lasers with equal intensity. The present application adopts the above scheme, reduces the number of PDs, and reduces the BOM cost. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0026] Figure 1 The circuit diagram of the backlight monitoring circuit of the traditional optical module;

[0027] Figure 2 The circuit diagram of the backlight monitoring circuit of the optical module provided by the embodiment of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0029] In the description of the present application, unless otherwise specified, the meaning of "multiple" and "several" is two or more.

[0030] Reference is made to Figure 2This invention provides a backlight monitoring circuit for an optical module, including a digital diagnostic unit, multiple lasers, and at least one backlight monitoring diode. The at least one backlight monitoring diode is used to simultaneously receive backlight from two lasers and generate photocurrent. Each backlight monitoring diode is connected to an ADC pin of the digital diagnostic unit. The digital diagnostic unit is used to collect the sum of the photocurrents generated by the backlight monitoring diodes through an ADC pin, calculate the change in the sum of the photocurrents based on the collected sum, compare the collected change in the sum of the photocurrents with a set fluctuation range, and determine whether a laser in a certain channel is in an abnormal state when the collected change in the sum of the photocurrents exceeds the set fluctuation range.

[0031] Each backlight monitoring diode can receive backlight from two lasers at the same intensity.

[0032] Furthermore, when the total change in the photocurrent of the backlight monitoring diodes exceeds the set fluctuation range, the digital diagnostic unit determines that the laser in one channel is in an abnormal state; otherwise, it determines that the laser in each channel is in a normal state.

[0033] Furthermore, when the total photocurrent of the backlight monitoring diodes I pd总 When the change exceeds the set fluctuation range, the digital diagnostic unit is used to sequentially determine whether the lasers of each channel are abnormal. When the abnormal channel is found, the specific steps for determining whether the laser of the nth channel is abnormal are as follows:

[0034] Given the bias current I of the laser in the nth channel. b1 The bias current of the lasers in the remaining channels is Ib0. The lasers in each channel emit light simultaneously, and the digital diagnostic unit samples and obtains Ib0. pd总1 ;

[0035] Given the bias current I of the laser in the nth channel. b2 The bias current of the lasers in the remaining channels is Ib0. The lasers in each channel emit light simultaneously, and the digital diagnostic unit samples and obtains Ib0. pd总2 ;

[0036] The rate of change Kn′ of Ipd in the nth channel is calculated as follows:

[0037]

[0038] The calculated Kn′ is compared with the preset Kn. If the difference between Kn′ and Kn is within the set allowable range, the laser of the nth channel is determined to be in normal condition; otherwise, the laser of the nth channel is determined to be in abnormal condition.

[0039] Further, the digital diagnosis unit is used to determine the Kn corresponding to the nth channel, and the determination method of the Kn corresponding to the nth channel is that only the nth channel is turned on, two bias currents are respectively given to the laser of the nth channel, only the laser of the nth channel emits light, and the digital diagnosis unit samples two photo-generated current values corresponding to the two bias currents respectively, a linear function is used for fitting according to the bias current and the corresponding photo-generated current value, and the Kn corresponding to the nth channel is solved.

[0040] Further, when it is judged that the laser state of the nth channel is abnormal, the emission light power Pn' of the laser of the channel is calculated and reported, and the calculation formula of the emission light power Pn' of the laser of the channel is: Wherein, kn is the slope obtained when the optical power of the nth channel is calibrated, and Pn is the optical power of the nth channel when the optical module works normally.

[0041] The determination method of kn is that only the nth channel is turned on, two bias currents are respectively given to the laser of the nth channel, only the laser of the nth channel emits light, and the optical power corresponding to the two bias currents is read by an optical power meter respectively, a linear function is used for fitting according to the bias current and the corresponding optical power, and the kn corresponding to the nth channel is solved.

[0042] Each backlight monitoring diode of the application receives the backlights of two lasers at the same time, when one backlight monitoring diode is used to receive the backlights of two lasers at the same time, the backlight monitoring diode and the corresponding two lasers are respectively located at the three vertices of an isosceles triangle, wherein the two lasers correspond to two base angles of the isosceles triangle, the backlight monitoring diode corresponds to the top angle of the isosceles triangle, and the backlight monitoring diode corresponds to the backlights of the two lasers, so that the backlight monitoring diode can receive the backlights of the two lasers with equal intensity.

[0043] Further, at least one sampling resistor is further included, the sampling resistor corresponds to the backlight monitoring diode one by one, the anode of each backlight monitoring diode is connected to one end of the corresponding sampling resistor, and the other end of the sampling resistor is grounded.

[0044] Further, when the sampling resistor is multiple, the resistances of the multiple sampling resistors are different.

[0045] Preferably, R2=k*R1, and the same applies to the following.

[0046] When the application has four lasers, the sampling resistor is two, which are sampling resistor R1 and sampling resistor R2, wherein R2=k*R1, such as R2=2*R1.

[0047] The cathode of each backlight monitoring diode is connected to the anode of the power supply.

[0048] The positive pole of each backlight monitoring diode is connected with an ADC pin of the digital diagnosis unit, and the negative pole of each backlight monitoring diode is connected with one end of an inductor, and the other end of the inductor is connected with a power supply VCC.

[0049] Further, a capacitor is connected in parallel across each sampling resistor.

[0050] Further, the digital diagnosis unit is an MCU with an ADC function.

[0051] The step of backlight monitoring of the optical module is as follows:

[0052] The optical module works, all channels are turned on, and the bias current of the laser of each channel is respectively given as I b0 , and the lasers of each channel emit light at the same time.

[0053] An ADC pin of the digital diagnosis unit collects the total photoelectric current I pd总 of the backlight monitoring diodes, and judges whether the change amount of the collected total photoelectric current I pd总 of the backlight monitoring diodes exceeds a set fluctuation range, if not, it indicates that the state of the laser of each channel is normal, and if yes, it indicates that the state of the laser of a channel is abnormal.

[0054] The change amount of the total photoelectric current I pd总 of the backlight monitoring diodes is as follows:

[0055] Wherein, I1 is I pd总 when the optical module works normally, and I2 is I pd总 obtained by the digital diagnosis unit in real time or periodically.

[0056] The transmitting end optical power is calibrated before the module is shipped, the two photoelectric currents I pd are respectively obtained by giving different bias currents to the laser, and then the slope k and the constant term b are obtained by using a linear function y=k*x+b, and then the optical power is calibrated.

[0057] Further, when the change amount of the total photoelectric current I pd总 of the backlight monitoring diodes exceeds the set fluctuation range, whether the laser of each channel is abnormal is judged in sequence, the abnormal channel is found, and when whether the laser of the nth channel is abnormal is judged, the specific steps are as follows:

[0058] The bias current of the laser of the nth channel is given as I b1 , the bias current of the laser of the remaining channels is given as I b0 , the lasers of each channel emit light at the same time, and I pd总1 is sampled by the digital diagnosis unit.

[0059] The bias current of the laser of the nth channel is I b2 The bias current of the laser of the rest channels is I b0 The lasers of each channel emit light at the same time, and the digital diagnosis unit samples I pd总2 ;

[0060] The rate of change Kn of I pd of the nth channel is calculated as follows:

[0061]

[0062] The calculated Kn' is compared with the preset Kn. When the difference between Kn' and Kn is within a set allowable range, it is determined that the state of the laser of the nth channel is normal, otherwise, it is determined that the state of the laser of the nth channel is abnormal.

[0063] Further, when it is determined that the state of the laser of the nth channel is abnormal, the emitted light power Pn' of the laser of the channel is calculated and reported, and the calculation formula of the emitted light power Pn' of the laser of the channel is as follows: where kn is the slope obtained when the optical power of the nth channel is calibrated, and Pn is the optical power of the nth channel when the optical module is normally working.

[0064] Further, the determination method of Kn corresponding to the nth channel is as follows: only the nth channel is turned on, two bias currents are respectively given to the laser of the nth channel, only the laser of the nth channel emits light, and the digital diagnosis unit samples two photo-generated current values corresponding to the two bias currents respectively, a linear function is used for fitting according to the bias currents and the corresponding photo-generated current values, and Kn corresponding to the nth channel is obtained.

[0065] The determination method of kn is as follows: only the nth channel is turned on, two bias currents are respectively given to the laser of the nth channel, only the laser of the nth channel emits light, the optical power corresponding to the two bias currents is respectively read by an optical power meter, a linear function is used for fitting according to the bias currents and the corresponding optical power, and kn corresponding to the nth channel is obtained.

[0066] The above process will be described in detail below by taking 100GLR4 as an example.

[0067] Firstly, the light emitting power P of the laser is determined by the bias current Ibias, and η is the light emitting efficiency of the laser: P = η * Ibias, Ibias is determined by the MCU, and Ibias of 100G LR4 is generally about 50mA per channel.

[0068] 100G LR4 has 4 channels, in normal operation, the working current is about 50mA, the optical power of each channel is about 2dBm (1.6mW). Before the module is shipped, the transmitting end optical power will be calibrated.

[0069] Open channel 1 alone, give the laser of channel 1 two different bias currents respectively, such as 40mA and 50mA, and read the corresponding optical power P0 and P1 with the optical power meter, then bring y=k*x+b, P0=k1*40+b1, P1=k1*50+b1, then from the above two equations, we can solve k1 and b1. In this way, the transmitting optical power is calibrated.

[0070] At the same time, when the laser emits light, the PD placed on the back of the laser will generate a photo current I pd For channel 1, give the laser two Ibias, such as 40mA and 50mA, the MCU will sample two I pd0 and I pd1 , then bring y=k*x+b, I pd0 =K1*40+B1, I pd1 =K1*50+B1, then from the above two equations, we can solve K1 and B1, and save in MCU, calibrate optical power. In the same way, respectively, laser 2, 3, 4 are calibrated to get K2, K3, K4.

[0071] Each channel has corresponding kn, bn and Kn, Bn, n is the number of channels.

[0072] From the characteristics of the laser and PD:

[0073] P∝Ibias∝I pd

[0074] So, in the case of the same light power, Ipd1=0.5*Ipd2.

[0075] From the above formula, the Ipd of different channels is quite different, which can accurately find the channel with large change.

[0076] Specifically as Figure 2 shown, and Figure 1Compared to other methods, this only occupies one pin of the MCU, saving three pins, which is considerable for high-speed optical modules. This invention simplifies the optical path, using only two backlight monitoring diodes, PD1 and PD2. The three optical elements PD1, LD1, and LD2 are located at the three vertices of an isosceles triangle, with PD1 corresponding to the vertex and LD1 and LD2 corresponding to the two base angles. Since the laser backlight is divergent, the backlight monitoring diode PD1 can receive the backlight from lasers LD1 and LD2 with equal intensity. Similarly, the three optical elements PD2, LD3, and LD4 are also located at the three vertices of an isosceles triangle, with PD2 corresponding to the vertex and LD3 and LD4 corresponding to the two base angles. The backlight monitoring diode PD2 can receive the backlight from lasers LD3 and LD4 with equal intensity.

[0077] Figure 2 In this context, R2 = 2 * R1. For the MCU, Figure 2 The ADC samples the sum of the photocurrents generated by the two PDs. Then, the algorithm can be used to monitor the optical power of each laser.

[0078] When all four lasers are emitting light simultaneously, the ADC1 pin of the MCU obtains:

[0079] Ipd_total = Ipd1 + Ipd2

[0080] The typical accuracy requirement for transmitted optical power is 3dB per channel. If I pd总 A change in power within 17% indicates that the optical power of each channel is stable and unchanged. If I pd总 If the change exceeds this fluctuation range, it indicates that the optical power of one or more channels has changed significantly (i.e., the change in optical power of one or more channels exceeds the accuracy requirement), which means that the slope of the laser has changed. At this time, it is necessary to find the corresponding channel.

[0081] When the optical module is working normally, all four channels emit light simultaneously. If the MCU periodically acquires I... pd总 If the change is within the set allowable range (e.g., 17%, but not limited to 17%, it can be set as needed), it indicates that each laser is in normal condition; if I pd总 If the change exceeds the set allowable range (e.g., 17%, but not limited to 17%, it can be set as needed), it indicates that there is an abnormal laser status and the reported optical power value needs to be updated.

[0082] Because the MCU's ADC samples I pd总So it is necessary to find the abnormal channel. At this time, it is necessary to make slight changes on the Ibiases of each channel to obtain the corresponding relationship between Ibiases and I pd总 . The bias currents of certain channels are changed respectively, such as I b1 =I b0 -δ, I b2 =I b0 +δ, δ can be 2mA, but is not limited to 2mA, and then the MCU sampling will also change accordingly. The change rate of the sampling at this time is compared with the recorded K1, K2, K3 and K4, so that it can be known whether the optical power of the channel has a large change, and then corresponding reporting is made.

[0083] The specific process is as follows:

[0084] 1) Given that the Ibiases of the four channels are 48mA, 50mA, 50mA, 50mA and 52mA, 50mA, 50mA, 50mA, the MCU will sample I pd总0 and I pd总1 . Since the Ibiases of channels 2, 3 and 4 are unchanged, the difference between I pd总1 and I pd总0 can reflect the change amount of the optical power of channel 1, and further reflect the change rate of I pd . It is defined that

[0085]

[0086] As known from the above calibration process, K represents the corresponding relationship between Ipd and Ibias. By comparing K1' and K1 in the calibration process, it can be known whether the laser of channel 1 is abnormal. If channel 1 is normal, no operation is needed; if channel 1 is abnormal, the emitted optical power of channel 1 needs to be calculated. At this time, the formula

[0087]

[0088] P1' is the emitted optical power of the laser at this time.

[0089] In the same way, it can be determined whether other channels are abnormal.

[0090] Embodiment two

[0091] The embodiment of the application further discloses a light module which adopts the backlight monitoring circuit as described in embodiment one.

[0092] The application realizes monitoring of the optical power of multiple lasers by only occupying one ADC pin of the MCU, saves the occupation of hardware resources and simplifies the layout space of the PCB in the case of the same function. On the optical path, the number of PDs is reduced, and the BOM cost is reduced.

[0093] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A back light monitoring circuit of an optical module, comprising a digital diagnostic unit, a plurality of lasers, characterized in that: The back light monitoring circuit further comprises at least one back light monitoring diode, the at least one back light monitoring diode is used for receiving back light of two lasers at the same time and generating photo-generated current, each back light monitoring diode is connected with an ADC pin of the digital diagnosis unit, the digital diagnosis unit is used for collecting the sum of photo-generated current of the back light monitoring diodes through the ADC pin, and calculating the change of the sum of photo-generated current of the back light monitoring diodes according to the collected sum of photo-generated current of the back light monitoring diodes, comparing the change of the collected sum of photo-generated current of the back light monitoring diodes with a set fluctuation range, and judging whether the laser of a channel is abnormal when the change of the collected sum of photo-generated current of the back light monitoring diodes exceeds the set fluctuation range. When one back light monitoring diode is used for receiving back light of two lasers at the same time, the back light monitoring diode and the corresponding two lasers are located at three vertices of an isosceles triangle, the two lasers correspond to two base angles of the isosceles triangle, the back light monitoring diode corresponds to a top angle of the isosceles triangle, and the back light monitoring diode corresponds to back light surfaces of the two lasers, so that the back light monitoring diode can receive back light of the two lasers with equal intensity.

2. The backlight monitoring circuit of the optical module of claim 1, wherein: The back light monitoring circuit further comprises at least one sampling resistor, the sampling resistor corresponds to the back light monitoring diode one by one, a positive electrode of each back light monitoring diode is connected with one end of the corresponding sampling resistor, and the other end of the sampling resistor is grounded; and a capacitor is connected in parallel between two ends of each sampling resistor.

3. The backlight monitoring circuit of the optical module of claim 2, wherein: When the sampling resistors are multiple, the resistances of the multiple sampling resistors are different.

4. The backlight monitoring circuit of claim 1, wherein: A positive electrode of each back light monitoring diode is connected with an ADC pin of the digital diagnosis unit, and a negative electrode of each back light monitoring diode is connected with one end of an inductor, and the other end of the inductor is connected with a power supply VCC.

5. The backlight monitoring circuit of claim 1, wherein: When the change of the collected sum of photo-generated current of the back light monitoring diodes exceeds the set fluctuation range, the digital diagnosis unit judges that the laser of a channel is abnormal, otherwise, the digital diagnosis unit judges that the laser of each channel is normal.

6. The backlight monitoring circuit of the optical module according to claim 5, wherein: When the total photocurrent of the backlight monitoring diodes I pd总 When the change exceeds the set fluctuation range, the digital diagnostic unit is used to sequentially determine whether the lasers of each channel are abnormal. When the abnormal channel is found, the specific steps for determining whether the laser of the nth channel is abnormal are as follows: The bias current of the laser of the nth channel is I b1 The bias current of the laser of the rest channels is I b0 The lasers of the respective channels emit light simultaneously, and the digital diagnosis unit samples I pd总1 ; The bias current of the laser of the nth channel is I b2 The bias current of the laser of the rest channels is I b0 The lasers of the respective channels emit light simultaneously, and the digital diagnosis unit samples I pd总2 ; calculating a rate of change of Ipd for the nth channel is: ； The calculated value is compared with a preset value The comparison result is compared with a preset value When the difference is within a preset allowable range, the laser state of the nth channel is determined to be normal, otherwise, the laser state of the nth channel is determined to be abnormal, The difference is compared with a preset allowable range The difference is compared with a preset allowable range The slope is obtained during the power calibration of the nth channel.

7. The backlight monitoring circuit of the optical module of claim 6, wherein: The digital diagnosis unit is used for determining the corresponding , the determination method of the corresponding of the nth channel is as follows: only the nth channel is turned on, two bias currents are respectively given to the laser of the nth channel, only the laser of the nth channel emits light, and two photogenerated current values corresponding to the two bias currents are respectively sampled by the digital diagnosis unit; according to the bias current and the corresponding photogenerated current value, a linear function is used for fitting, and the corresponding of the nth channel is obtained.

8. The backlight monitoring circuit of the optical module as described in claim 6, characterized in that: When judging that the state of the laser of the nth channel is abnormal, the digital diagnosis unit is used to calculate the emission optical power of the laser of the channel and report, the calculation formula of the emission optical power of the laser of the channel is: wherein, is the slope obtained when the optical power of the nth channel is calibrated, is the optical power of the nth channel when the optical module works normally.​ 9. An optical module characterized by comprising: The back light monitoring circuit is used. The back light monitoring circuit is used.

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