CN116232449A - Detection circuit for detecting received signal strength and signal loss of optical receiver - Google Patents

Abstract

The invention discloses a detection circuit for detecting the intensity of a received signal and the loss of the signal of an optical receiver, which comprises a micro control unit MCU, an avalanche photodiode APD, a hysteresis comparison circuit and a main control unit with a boosting function and a two-path mirror image current output function; the micro control unit MCU detects the intensity of the optical signal by receiving one path of mirror current output by the main control unit; the hysteresis comparison circuit detects loss of the optical signal through the voltage signal converted from the other path of mirror current output by the main control unit and the voltage signal output by the MCU. The invention can realize the RX Power detection and the LOS detection of the received light on the 50G PON ONU simultaneously by combining the existing chip and the hysteresis comparison circuit, and effectively solves the technical problem that the current 50G PON ONU can not realize the RX Power detection and the LOS detection simultaneously without a special LA chip.

Description

A detection circuit for detecting received signal strength and signal loss of optical receiver

technical field

The invention relates to the technical field of optical communication, in particular to a detection circuit for detecting received signal strength and signal loss of an optical receiver, and is especially suitable for detecting the signal strength and signal loss of light received by a 50G PON ONU.

Background technique

In the optical fiber communication system, the task of the optical receiver is to restore the information carried by the optical carrier after optical fiber transmission with the minimum additional noise and distortion. Therefore, the output characteristics of the optical receiver comprehensively reflect the performance of the entire optical fiber communication system.

In order to ensure stable and reliable transmission of optical signals, it is necessary to perform signal strength (RX Power) detection and loss of signal (LOS, Loss of signal) detection on received optical signals in practical applications. RX Power detection refers to the detection of the received optical signal strength, which is used to judge whether the received signal strength meets the requirements. LOS detection refers to detecting whether the intensity of the received optical signal is lower than the set threshold value, so as to judge whether the signal exceeds the acceptable range. According to the design and register configuration of the optical module, LOS detection can be summarized into two implementation methods: average optical power LOS and signal LOS. The average optical power LOS is judged according to the magnitude of the average optical power of the input light, and the signal LOS is judged according to the magnitude of the signal in the input light. When the strength of the received optical signal is lower than a certain threshold value, the optical module needs to report LOS. Specifically, there are LOSA, LOSD and LOSH indicators. Wherein, the LOSA indicator refers to a signal loss indication, and it is judged that the signal confirmation is lost when the strength of the received optical signal is less than a certain threshold. The LOSD indicator refers to the indicator of signal loss recovery. When the strength of the received optical signal is greater than a certain threshold, it is judged that the signal is confirmed to be restored. Since the comparison is realized by using a comparator with a certain hysteresis effect, generally the optical power value corresponding to the LOSD index is larger than the value corresponding to the LOSA index. The LOSH indicator refers to the signal loss hysteresis, and the comparator is a hysteresis comparator, which is reflected in the power value to represent the power difference between signal loss and loss recovery.

In the prior art, for PON ONUs with a rate of 10G and below, two paths are used to respectively implement RX Power detection and LOS detection, as follows:

RX Power detection: As shown in Figure 2, since most PON ONUs use APD (Avalanche Photodiode Detectors) to receive optical signals, the boost circuit is usually used to mirror the APD current to realize the detection of RX Power.

LOS detection: It is detected by the signal differential amplitude detection and judgment method (that is, the signal LOS). As shown in Figure 2, the photocurrent is generated after the received light enters the APD, and the photocurrent is converted into The differential output voltage is connected to the LA chip (Limiting Amplifier, limiting amplifier chip) to limit and amplify the signal. The LA chip will collect the received input signal level swing and compare it with the set LOS threshold level, and finally output LOS Signal.

Through the above detection method, the intensity detection of the PON ONU optical signal and the loss detection of the optical signal at a rate of 10G and below can be effectively realized. However, with the continuous innovation of business applications, gigabit optical networks are changing from the gigabit connection capability of "bandwidth" to the gigabit service capability of "bandwidth + experience". For example, industrial PON helps the digital transformation of factories, and FTTR helps people enjoy digital life etc. At the same time, at the technical level, whether it is a standard or a solution, the evolution from 10G PON to 50G PON is a foregone conclusion. However, since the current 50G PON does not have a dedicated LA chip, the LOS detection of the signal cannot be realized by detecting the signal amplitude through the LA chip.

In addition, the patent document with the publication number CN104168067A also discloses a method for judging the optical power signal strength in the optical receiving circuit and its circuit. The method realizes the judgment of the optical power signal strength of the optical receiving circuit through software, and can realize the signal strength detection. However, this method also uses a dedicated limiting amplifier chip to integrate the signal amplitude detection and comparator functions. It also cannot realize the RX Power detection function and the LOS detection function at the same time under the premise that there is no 50G rate PON limiting amplifier chip at present.

For this reason, it is necessary to use the technology under the existing conditions to solve the above technical problems on the basis that the current 50G PON does not have a dedicated LA chip.

Contents of the invention

The purpose of the present invention is to provide a detection circuit for detecting the received signal strength and signal loss of the optical receiver. The detection circuit can realize the RX of the received light on the 50G PON ONU at the same time through the combination of the existing chip and the hysteresis comparison circuit. Power detection and LOS detection effectively solve the technical problem that the current 50G PON does not have a dedicated LA chip and cannot simultaneously realize RXPower detection and LOS detection.

To achieve the above object, the technical scheme adopted in the present invention is as follows:

A detection circuit for detecting the received signal strength and signal loss of an optical receiver, characterized in that it includes a micro control unit MCU, an avalanche photodiode APD, a hysteresis comparison circuit and a main control unit with a boost function and two mirror current output functions unit;

The main control unit includes a main control chip, a boost circuit, a first voltage conversion circuit and a second voltage conversion circuit, and the main control chip has a high-voltage input pin, a high-voltage output pin, a voltage feedback pin, and a 1/5 mirror image The first mirror current pin of the ratio and the second mirror current pin of the 1/2 mirror ratio;

The hysteresis comparison circuit has a first voltage input terminal, a second voltage input terminal and a signal output terminal;

The micro control unit MCU includes comparison voltage output DAC pins, boost control DAC pins and mirror current receiving ADC pins;

The avalanche photodiode APD has a voltage input pin;

Wherein, the boost circuit is respectively connected with the voltage feedback pin of the main control chip and the boost control DAC pin of the micro control unit MCU, the high voltage output pin of the main control chip is connected with the voltage input pin of the avalanche photodiode APD, and the main The first mirror current pin of the control chip is converted into a voltage by the first voltage conversion circuit and then connected to the MCU mirror current receiving ADC pin of the micro control unit, and the second mirror current pin of the main control chip is converted into a voltage by the second voltage conversion circuit. The voltage is connected to the second voltage input end of the hysteresis comparison circuit, and the comparison voltage output DAC pin of the micro control unit MCU is connected to the first voltage input end of the hysteresis comparison circuit;

The micro control unit MCU detects the intensity of the optical signal by receiving the converted voltage received by the ADC pin through the mirror current; the hysteresis comparison circuit detects the intensity of the optical signal through the voltage signal input from the first voltage input end and the second voltage input end loss, and output the detection result of signal loss.

The first voltage conversion circuit includes a first resistor with one end connected to the ground and the other end connected to the first mirror current pin.

The second voltage conversion circuit includes a second resistor with one end connected to the ground and the other end connected to the second mirror current pin.

A third resistor is provided between the high voltage output pin of the main control chip and the voltage input pin of the avalanche photodiode APD.

A fourth resistor and a fifth resistor are connected in series between the comparison voltage output DAC pin of the micro control unit MCU and the first voltage input terminal of the hysteresis comparison circuit, and a grounding capacitor is arranged between the fourth resistor and the fifth resistor .

A ground capacitor and a sixth resistor are sequentially provided between the second mirror current pin of the main control chip and the second voltage input terminal of the hysteresis comparator circuit.

The signal output terminal of the hysteresis comparator circuit is further connected in series with a seventh pull-up resistor and an eighth resistor in series.

The advantage of adopting the present invention is:

1. The present invention can realize RX Power detection and LOS detection of received light on the 50G PON ONU at the same time through the combination of the main control chip with the boost function and the two-way mirror current output function and the hysteresis comparison circuit. It effectively solves the technical problem that the current 50G PON ONU cannot realize RX Power detection and LOS detection at the same time without a dedicated LA chip. Compared with the prior art, the present invention has achieved new technical effects through the combination of the prior art, or the combined technical effect is superior to the sum of the effects of each technical feature, so the present invention has unexpected technical effect.

2. The present invention realizes the sampling detection and small light LOS detection under the full dynamic range of RX Power at the same time through an integrated chip with boost and dual mirror output and an external hysteresis comparison circuit, which is original in the solution.

3. The present invention facilitates converting the mirror current with a ratio of only 1/2 to an appropriate voltage value through the second resistor, which is beneficial to the comparison and judgment of the subsequent circuit.

4. The present invention can adjust the working bias voltage of the APD under high light through the third resistor. Since the output voltage of the high-voltage output pin of the main control chip is constant, the greater the photocurrent generated under the high light condition, the higher the third resistor will be. The more the divided voltage is, the lower the working voltage for the avalanche photodiode APD will be, which is beneficial to increase the gain of the avalanche photodiode APD under large light.

5. The present invention can play a role by the fourth resistance, the fifth resistance and the ground capacitance between the micro control unit MCU and the hysteresis comparison circuit, and the sixth resistance and the ground capacitance between the main control chip and the hysteresis comparison circuit. To the effective bypass filtering effect, which is conducive to improving the accuracy of detection.

6. In the present invention, the seventh pull-up resistor connected to the signal output terminal of the hysteresis comparator circuit is beneficial to ensure the stable output of the voltage.

Description of drawings

Fig. 1 is a circuit block diagram of the present invention;

Fig. 2 is a functional block diagram of implementing RX Power detection and LOS detection in the prior art.

Detailed ways

Since the 50G PON ONU does not have a dedicated LA chip that can be used to detect signal amplitude and output LOS, the present invention considers that the LOS function (that is, the average optical power LOS) can also be realized by detecting RX Power. It is required that the mirror current of the avalanche photodiode APD must be It can realize the RX Power detection function and the LOS detection function. Therefore, a chip with an integrated boost function and two mirror current outputs is designed with a peripheral hysteresis comparison circuit to simultaneously realize RXPower detection and LOS signal detection.

The present invention is specifically described below in conjunction with accompanying drawing:

As shown in Figure 1, a detection circuit for detecting the received signal strength and signal loss of an optical receiver, including a micro control unit MCU, an avalanche photodiode APD, a hysteresis comparison circuit and a circuit with a boost function and two mirror current output functions main control unit.

The main control unit includes a main control chip, a boost circuit, a first voltage conversion circuit and a second voltage conversion circuit. Among them, the main control chip preferably adopts the EOC7003 chip, and has a high-voltage input pin MIRIN, a high-voltage output pin MIROUT, a voltage feedback pin FB, a first mirror current pin MIR1 with a mirror ratio of 1/5, and a mirror ratio of 1/2 The second mirror current pin MIR2.

The hysteresis comparison circuit has a first voltage input terminal Up, a second voltage input terminal Un and a signal output terminal Uo.

The micro control unit MCU includes a comparison voltage output DAC pin H5, a boost control DAC pin H6 and a mirror current receiving ADC pin G7.

The avalanche photodiode APD has a voltage input pin Vapd.

Among them, the specific connection relationship of each component is as follows: the boost circuit is connected to the voltage feedback pin FB of the main control chip and the boost control DAC pin H6 of the micro control unit MCU, and the high-voltage output pin MIROUT of the main control chip is connected to the avalanche The voltage input pin Vapd of the photodiode APD is connected, the first mirror current pin MIR1 of the main control chip is converted into a voltage by the first voltage conversion circuit, and then connected to the mirror current receiving ADC pin G7 of the micro control unit MCU, the main control chip The second mirror current pin MIR2 is converted into a voltage by the second voltage conversion circuit and connected to the second voltage input terminal Un of the hysteresis comparison circuit, and the comparison voltage output DAC pin H5 of the micro control unit MCU is connected to the hysteresis comparison circuit. The first voltage input terminal Up is connected, and the signal output terminal Uo of the hysteresis comparison circuit is connected to the QSFP28 Connector (the QSFP28 Connector is a QSFP28 package connector, which is actually the electrical interface of the module and follows the QSFP28MSA protocol).

In an embodiment of the present invention, the first voltage conversion circuit includes a first resistor R9 with one end connected to the ground and the other end connected to the first mirror current pin MIR1, and the resistance of the first resistor R9 is 6.04 kohm.

In an embodiment of the present invention, the second voltage conversion circuit includes a second resistor R7 with one end connected to the ground and the other end connected to the second mirror current pin MIR2, and the resistance of the second resistor R7 is 20 kohm.

In an embodiment of the present invention, a third resistor R6 is provided between the high voltage output pin MIROUT of the main control chip and the voltage input pin Vapd of the avalanche photodiode APD.

In an embodiment of the present invention, a fourth resistor R11 and a fifth resistor R12 are connected in series between the comparison voltage output DAC pin H5 of the micro control unit MCU and the first voltage input terminal Up of the hysteresis comparison circuit, and the first A ground capacitor C8 is provided between the fourth resistor R11 and the fifth resistor R12.

In an embodiment of the present invention, a grounding capacitor C10 and a sixth resistor R15 are sequentially arranged between the second mirror current pin MIR2 of the main control chip and the second voltage input terminal Un of the hysteresis comparison circuit.

In an embodiment of the present invention, the signal output terminal Uo of the hysteresis comparison circuit is further connected in series with a seventh pull-up resistor R13 and an eighth resistor R14, the resistance of the seventh pull-up resistor R13 is 10 kohm, the pull-up To VCC3V3, make sure the high level output is stable to 3V3.

When it is necessary to detect the signal strength of the received light, the main control chip outputs a mirror current of 1/5 mirror image ratio to the micro control unit MCU through the first mirror current pin MIR1, and the micro control unit MCU receives the mirror current through the mirror current receiving ADC pin G7 The conversion voltage of the mirror current is then sampled by the ADC to realize the detection of RX Power.

When it is necessary to detect the loss of the received light signal, the main control chip outputs a mirror current with a mirror ratio of 1/2 through the second mirror current pin MIR2, and the mirror current is converted into a voltage signal by the second voltage conversion circuit and then input to the hysteresis comparison The second voltage input terminal Un of the circuit, at the same time, the micro control unit MCU inputs a preset threshold voltage signal to the first voltage input terminal Up of the hysteresis comparison circuit through the comparison voltage output DAC pin H5, and the hysteresis comparison circuit converts the main control chip The input voltage signal is compared with the preset threshold voltage signal to determine whether there is light loss, and after the comparison is completed, the detection result of signal loss is output to realize LOS detection.

The boosting principle of the present invention and mirror image current collection principle are respectively:

Boost principle: As shown in Figure 1, the voltage feedback pin FB of the EOC7003 main control chip is the feedback input pin, the reference voltage is 1.24V, the DAC_VAPD_MCU is connected to the boost control DAC pin of the micro control unit, and the resistors R2 and R4 Connect with resistor R5 as shown in Figure 1 to form a boost circuit, the specific relationship is:

IR5=VFB/R5;

IR2=(VMIRIN-VFB)/R2;

IR4=IR5-IR2=(DAC_VAPD_MCU-VFB)/R4;

According to the above three formulas, the relationship between DAC_VAPD_MCU and VMIRIN can be obtained as:

VMIRIN=R2*(VFB/R5+VFB/R4-DAC_VAPD_MCU/R4)+VFB.

Thus, the output of the DAC_VAPD_MCU can adjust the VMRIN high voltage input to the high voltage input pin MIRIN of the EOC7003 main control chip. According to the parameters set in Figure 1, VMRIN can cover the APD bias working range (16~34V) with an accuracy of ~0.018V/LSB.

Mirror current acquisition principle: the high voltage output pin MIROUT of the EOC7003 main control chip is a high voltage output, and VMIROUT=VMIRIIN-1.7V. Connect to the avalanche photodiode APD through VAPD_APD_TO to provide it with a bias operating point and monitor its current (when light shines on the APD, a photocurrent will be generated), and the first mirror current pin MIR1 of the EOC7003 master chip and the second The mirror current pin MIR2 is used as the mirror current output of the current in proportions of 1/5 and 1/2 respectively. The current mirrored by the first mirror current pin MIR1 is converted into a voltage through the grounded first resistor R9 and connected to the micro control unit MCU to realize ADC sampling and complete the detection of RX Power. The current mirrored by the second mirror current pin MIR2 is converted into a voltage through the grounded second resistor R7 and compared with another input signal DAC_LOSLVL_MCU of the hysteresis comparator circuit to output the LOS signal.

The RX Power detection and LOS detection of the present invention will be described in detail below by taking a 50G PON ONU as an example and referring to FIG. 1 .

According to the ITU-T G9804.3 protocol, the receiving sensitivity of the 50G PON ONU N1/C+ gear is -24dBm, and the receiving overload optical power is -3dBm. The detection and reporting of Rx Power must at least cover the sensitivity to the overload area, while the LOS power point needs to less than receiver sensitivity.

Sampling implementation of Rx Power detection: the responsivity of 50G APD (the efficiency of converting optical power into photocurrent) is generally around 4mW/mA. It can be seen from this that Iapd=IMIROUT≈15.9uA corresponding to the sensitivity point and Iapd= IMIROUT ≈ 2mA. And because IMIR1=1/5*IMIROUT, sampling resistor R9=6.04kohm, ADC_RXPower_MCU from sensitivity to overload range is 19.2mV to 2.42V, which meets the MCU ADC sampling voltage range (conventional MCU ADC reference voltage full-scale 2.5V). This effectively implements the Rx Power detection function.

Realization of LOS detection function: Since there is no dedicated LA chip, the LOS detection function is realized through the hysteresis comparison circuit shown in Figure 1 . DAC_LOSLVL_MCU is connected to the step-up control DAC pin of the micro control unit MCU, and connected to the non-inverting input terminal of the hysteresis comparison circuit to realize the setting of the LOS judgment threshold reference voltage, which is output from the second mirror current pin MIR2 of the EOC7003 main control chip V_RXPower is compared with it as an input value, and realizes the electrical interface output of RX_LOS_Finger connected to the optical module.

According to the hysteresis comparison circuit design shown in Figure 1:

When Uo=+Uz=VCC3V3;

Up=R10/(R10+R12)*DAC_LOSLVL_MCU+R12/(R10+R12)*Uz;

At the time of V_RXPOWER=Un=Up, the circuit is in a critical state, and V_RXPOWER at this time is the threshold value Uth, that is, Uth=R10/(R10+R12)*DAC_LOSLVL_MCU+R12/(R10+R12)*VCC3V3;

When Uo=-Uz=0;

Up=R10/(R10+R12)*DAC_LOSLVL_MCU+R12/(R10+R12)*Uz;

In the same way:

Utl= R10/(R10+R12)*DAC_LOSLVL_MCU;

Hysteresis voltage △U=Uth-Utl=R12/(R10+R12)*VCC3V3.

Applied to the present invention, if the LOS interval is LOSD<-24.5dBm (ie 3.55uW), LOSA>-40dBm (ie 0.1uW). Then the photocurrent at the LOSD power point is about 14.2uA, that is, Iapd=IMIROUT≈14.2uA, IMIR2=1/2*IMIROUT=7.1uA, at this time, V_RXPower=IMIR2*R7=141.9mV, in order to ensure LOSD<-24.5dBm , Uth of the hysteresis comparator circuit must be ≤141.9mV.

According to the parameters shown in Figure 1, the received input optical power -26dBm corresponds to V_RXPower≈100.5mV, and the Uth corresponding to the hysteresis comparator is 140.0mV, which is close to the corresponding V_RXPower (141.9mV) when LOSD=24.5dBm, and Utl is 99.2mV . Therefore, DAC_LOSLVL_MCU can be set to 100.5mV. If V_RXPower>140.0mV, the RX_LOS_Finger output is determined to be low level, telling the host that the signal is restored at this time; and if V_RXPower<99.2mV, the RX_LOS_Finger output is determined to be high level (VCC3V3), Inform the host that the signal is lost at this time; the interval between them is the hysteresis interval, thus effectively realizing the LOS detection function.

In general, the present invention can simultaneously realize the RX Power detection and LOS detection of received light on the 50G PON ONU through the combination of the main control chip with the boost function and the two-way mirror current output function and the hysteresis comparison circuit. , thus effectively solving the technical problem that the current 50G PON ONU cannot simultaneously realize RX Power detection and LOS detection without a dedicated LA chip.

The above is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless specifically stated, can be replaced by other equivalent or alternative features with similar purposes; all features disclosed, or all The steps of a method or process may be combined in any way, except for mutually exclusive features and/or steps.

Claims (7)

1. A detection circuit for detecting received signal strength and signal loss of an optical receiver, characterized by: the device comprises a micro control unit MCU, an avalanche photodiode APD, a hysteresis comparison circuit and a main control unit with a boosting function and a two-path mirror current output function;

the main control unit comprises a main control chip, a boost circuit, a first voltage conversion circuit and a second voltage conversion circuit, and the main control chip is provided with a high-voltage input pin, a high-voltage output pin, a voltage feedback pin, a first mirror current pin with 1/5 mirror proportion and a second mirror current pin with 1/2 mirror proportion;

the hysteresis comparison circuit is provided with a first voltage input end, a second voltage input end and a signal output end;

the micro control unit MCU comprises a comparison voltage output DAC pin, a boost control DAC pin and a mirror current receiving ADC pin;

the avalanche photodiode APD has a voltage input pin;

the voltage feedback pin of the main control chip is connected with the voltage input pin of the avalanche photodiode APD, the first mirror current pin of the main control chip is converted into voltage by the first voltage conversion circuit and then is connected with the mirror current receiving ADC pin of the micro control unit MCU, the second mirror current pin of the main control chip is converted into voltage by the second voltage conversion circuit and then is connected with the second voltage input end of the hysteresis comparison circuit, and the comparison voltage output DAC pin of the micro control unit MCU is connected with the first voltage input end of the hysteresis comparison circuit;

the micro control unit MCU detects the intensity of an optical signal through the conversion voltage received by the mirror current receiving ADC pins; the hysteresis comparison circuit detects loss of the optical signal through the voltage signals input by the first voltage input end and the second voltage input end, and outputs a detection result of the loss of the signal.

2. A detection circuit for detecting received signal strength and signal loss of an optical receiver as defined in claim 1, wherein: the first voltage conversion circuit comprises a first resistor, one end of which is grounded, and the other end of which is connected with a first mirror current pin.

3. A detection circuit for detecting received signal strength and signal loss of an optical receiver as defined in claim 1, wherein: the second voltage conversion circuit comprises a second resistor, one end of which is grounded, and the other end of which is connected with a second mirror current pin.

4. A detection circuit for detecting received signal strength and signal loss of an optical receiver as defined in claim 1, wherein: and a third resistor is arranged between the high-voltage output pin of the main control chip and the voltage input pin of the avalanche photodiode APD.

5. A detection circuit for detecting received signal strength and signal loss of an optical receiver as defined in claim 1, wherein: a fourth resistor and a fifth resistor are connected in series between a comparison voltage output DAC pin of the micro control unit MCU and a first voltage input end of the hysteresis comparison circuit, and a grounding capacitor is arranged between the fourth resistor and the fifth resistor.

6. A detection circuit for detecting received signal strength and signal loss of an optical receiver as defined in claim 1, wherein: and a grounding capacitor and a sixth resistor are sequentially arranged between the second mirror current pin of the main control chip and the second voltage input end of the hysteresis comparison circuit.

7. A detection circuit for detecting received signal strength and signal loss of an optical receiver as defined in claim 1, wherein: the signal output end of the hysteresis comparison circuit is also sequentially connected with a seventh pull-up resistor and an eighth resistor in series.

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