CN104821478A - Integratable automatic debugging circuit for optical eye pattern transmitted by optical module - Google Patents

Abstract

An integrated optical module sending optical eye diagram automatic debugging circuit relates to the optical module. There are algorithm module, Ibias current DAC module, Imod current DAC module, Ibias current monitoring module, and Imod current monitoring module; the output terminals of the algorithm module are respectively connected to the input terminal of Ibias current DAC module and the input terminal of Imod current DAC module, and the output terminal of Ibias current DAC module The terminal is connected to the input terminal of the Ibias current monitoring module, the output terminal of the Imod current DAC module is connected to the input terminal of the Imod current monitoring module, the Ibias current output terminal of the Ibias current monitoring module and the Imod current output terminal of the Imod current monitoring module are respectively connected to the input terminal of the laser driver chip ; The Ibias current monitoring module and the Imod current monitoring module are connected back to the algorithm module.

Description

A kind of automatic debugging circuit of optical module transmitting optical eye diagram that can be integrated

technical field

The invention relates to an optical module, in particular to an integrated automatic debugging circuit for sending an optical eye diagram of the optical module.

Background technique

The optical fiber communication network is connected to the access network of the user terminal. Due to the development of network broadband demand, the technology of the access network is performing a wave of "light advances copper and retreats". Passive optical network is widely used because of its easy maintenance, easy installation and expansion, and GPON (Gigabit-capable Passive Optical Network, Gigabit-capable Passive Optical Network) has become the best solution for optical fiber access. GPON is a point-to-multipoint structure, which can flexibly form tree, star, bus and other topological structures. GPON is composed of OLT (Optical Line Termination) installed in the central control station and installed in the user's place. The optical network unit ONU (Optical Network Unit, optical network unit) and the passive optical network ODN (Optical Distribution Network) between the OLT and the ONU. The GPON system adopts WDM (Wavelength Division Multiplexing) wavelength division multiplexing technology to realize single-fiber bidirectional transmission. The broadcast mode is implemented in the downlink direction from OLT to ONU, and the burst mode is used in the uplink direction from ONU to OLT.

The optical module is the core component of the ONU, mainly including laser driver chips, laser components, to achieve optical/electrical, electrical/optical signal conversion, BOSA (Bi-direction Optical Sub Assembly, optical transceiver integrated component) is the core device of the ONU optical module, Including the sending end and the receiving end, the rate of the sending end is 1.25Gbps, and the rate of the receiving end component is 2.488Gbps. At the sending end, the 1310nm laser light emitted by the laser passes through the optical waveguide and reaches the front end of the filter at a certain angle, where it is completely reflected by the end face and enters the optical fiber, while the 1310nm optical signals coming in from the optical fiber can all pass through the filter and be converted into electrical signals to realize the single-fiber bidirectional function. In order to monitor the working state of the laser and realize automatic power adjustment, about 10% of the light emitted by the laser enters the branch waveguide, is absorbed by the monitoring diode, and is transformed into a monitoring signal. The transmit optical eye diagram is the most critical indicator of the ONU transmitting end. The eye diagram contains rich information, reflects the overall characteristics of the digital signal, and can effectively evaluate the quality of the digital signal. If the quality of the optical eye diagram is not good, it will seriously affect the service capability between the ONU and the OLT.

The laser diode is a current control device, and its forward current exceeds the threshold current Ith to emit light. In general, in order to realize fast turn-on and turn-off, a DC bias current Ibias slightly greater than the threshold current will be added to the laser diode; the output of the laser depends on Its driving current amplitude and slope efficiency, its threshold current Ith and slope efficiency are all related to temperature, and the discrete type is relatively large.

The Chinese Patent Publication No. CN201010519598.7 "A Method for Automatically Debugging the Optical Eye Diagram of an Optical Module" is to obtain the threshold current of the laser, and then set the bias current of the optical module to the sum of the threshold current and the balance coefficient through the computer. Automatically debug the optical eye diagram without manual debugging.

Chinese Patent Publication No. CN 201110177788.X "A Method for Stable EML TOSA Output Optical Eye Diagram" only has the temperature compensation lookup table of the core temperature of the transmitting end module indexed by the module temperature, and Ibias current, Imod current, The temperature compensation lookup table for bias voltage and cross point is indexed by the core temperature of the transmitter module, and this method makes the optical eye diagram output by the module more stable.

The traditional optical module eye diagram debugging method is: use an eye diagram instrument and an optical power meter, adopt point-by-point adjustment, test, and then debug until the requirements are met, and the efficiency is very low. It takes about 5 minutes to complete the debugging of each module, and the debugging process is strongly dependent on the eye. Plotter and optical power meter, if there is no eye diagram, the quality of the eye diagram will not be known, and the dependence on the instrument is too strong. At present, the commonly used eye diagram instruments are mainly from Tektronix and Agilent, but the calculation methods inside the instruments are different, so the judgment of the eye diagram debugging results will also be affected. In addition, the instrument needs main temperature compensation, dark current calibration, etc. during use. If you forget, it will lead to test failure and affect the test efficiency of the optical eye diagram. At present, in order to prevent changes in the quality of the eye diagram under high and low temperature environments, a temperature compensation table is established for the extinction ratio of the eye diagram, and the transmitted optical power does not change much under high and low temperature conditions.

Contents of the invention

The purpose of the present invention is to provide a device that can be integrated in the laser driver chip, can debug the appropriate transmission optical power and extinction ratio, can realize the manual debugging of the optical eye diagram, improve the debugging efficiency of the optical eye diagram, and reduce the debugging cost. The integrated optical module sends the automatic debugging circuit of the optical eye diagram.

The present invention is provided with an algorithm module, an Ibias current digital-to-analog conversion module, an Imod current digital-to-analog conversion module, an Ibias current monitoring module, and an Imod current monitoring module; the Ibias current represents a DC bias current, and the Imod current represents a debugging current;

The output terminal of the algorithm module is respectively connected to the input terminal of the Ibias current digital-analog conversion module and the input terminal of the Imod current digital-analog conversion module, the output terminal of the Ibias current digital-analog conversion module is connected to the input terminal of the Ibias current monitoring module, and the output terminal of the Imod current digital-analog conversion module The terminal is connected to the input terminal of the Imod current monitoring module, the Ibias current output terminal of the Ibias current monitoring module and the Imod current output terminal of the Imod current monitoring module are respectively connected to the input terminal of the driver chip of the laser; the Ibias current monitoring module and the Imod current monitoring module are connected back to the Algorithm module.

The working principle of the present invention is as follows:

Use the Ibias current digital-to-analog converter (Digital to Analog Converter, DAC) module, Ibias current monitoring module, Imod current digital-analog conversion module, and Imod current monitoring module to realize automatic detection inside the laser driver chip, and then according to the feedback data in the internal algorithm module according to The calculation formulas of transmit optical power Power and extinction ratio ER are used to automatically adjust the DA value (hexadecimal number in the register) corresponding to Ibias current and Imod current until the appropriate transmit optical power and extinction ratio are debugged. In this way, the manual debugging of the optical eye diagram is realized. Improve the debugging efficiency of the optical eye diagram and reduce the debugging cost.

According to the calculation formula of the transmitted optical power: Pwr=(Imod/2+Ibias-Ith)*S (S is the slope efficiency of the laser, and Ith is the threshold current of the laser, both of which are provided by the optical module manufacturer), and the transmitted optical power specified by the ONU The optimal value and range of power. According to the calculation formula of the extinction ratio of the transmit optical eye diagram: ER=10lg[(Imod+Ibias-Ith)/(Ibias-Ith)], and the optimal value and range of the extinction ratio of the transmit optical eye diagram specified by the ONU.

The present invention integrates a function module that automatically adjusts the DA value corresponding to the Ibias current and the Imod current in the original laser driver chip, and adopts the gradually approaching The method automatically adjusts the internal registers of the chip, automatically debugs the appropriate DA value corresponding to the Ibias current and the Imod current, and outputs the Ibias current and the Imod current to drive the laser to work normally.

Through this integrated circuit, the automatic debugging of the optical eye diagram of the optical module can be realized. Compared with the traditional debugging method of the optical eye diagram of the optical module, it saves the tedious manual debugging, saves manpower and equipment costs, and avoids human subjectivity. Factors and instrument errors affect the judgment of the quality of the optical eye diagram.

Description of drawings

Fig. 1 is a block diagram of the structure composition of the embodiment of the present invention.

Fig. 2 is a schematic diagram of a laser transmitter matching circuit integrated with an embodiment of the present invention.

Fig. 3 is a characteristic analysis diagram of a laser driving circuit integrated with an embodiment of the present invention.

Fig. 4 is a flow chart of automatic debugging of the eye diagram when using the embodiment of the present invention.

Figure 5 is a flow chart of traditional optical eye diagram manual debugging.

Detailed ways

Referring to Fig. 1, the embodiment of the present invention is provided with algorithm module 1, Ibias current digital-to-analog conversion module 2, Imod current digital-to-analog conversion module 3, Ibias current monitoring module 4, Imod current monitoring module 5; Described Ibias current represents DC bias Current, Imod current represents the debugging current. The output terminal of the algorithm module 1 is respectively connected to the input terminal of the Ibias current digital-analog conversion module 2 and the input terminal of the Imod current digital-analog conversion module 3, the output terminal of the Ibias current digital-analog conversion module 2 is connected to the input terminal of the Ibias current monitoring module 4, and the Imod current digital The output terminal of the analog conversion module 3 is connected to the input terminal of the Imod current monitoring module 5, and the Ibias current output terminal of the Ibias current monitoring module 4 and the Imod current output terminal of the Imod current monitoring module 5 are respectively connected to the driver chip input terminal of the laser 6; the Ibias current The monitoring module 4 and the Imod current monitoring module 5 are connected back to the algorithm module 1 again. In FIG. 1, numeral 100 denotes the present invention.

When in use, the present invention can be integrated in the driver chip of the laser, wherein the algorithm module calculates and adjusts the DA value of the Ibias current and Imod current according to the calculation formula of Pwr and ER; the DA value of the Ibias current is input to the Ibias current digital-to-analog conversion module The circuit can realize the digital-to-analog conversion of Ibias. The output Ibias current value is input to the Ibias current monitoring module. The Ibias current is fed back to the algorithm module circuit one way, and one way is used as the output of the laser chip to provide the laser as the bias current of the laser diode. The DA value of the Imod current is input to the Imod current digital-to-analog conversion module circuit, which can realize the digital-to-analog conversion of Imod. The output Imod current value is input to the Imod current monitoring module, and the Imod current is fed back to the algorithm module circuit one way, and one way is output as a laser chip. The modulation current supplied to the laser as a laser diode. The appropriate DA value finally debugged by the algorithm module corresponds to the output bias current Ibias and the modulation current Imod to drive the laser to work normally.

Referring to Fig. 2, the appropriate DA value finally debugged by the present invention 100 integrated in the driver chip 61 of the laser corresponds to the output Ibias current and Imod current to drive the normal operation of the laser, and needs to be matched with a suitable laser sending end The circuit can guarantee the quality of the optical eye diagram at the sending end.

Figure 3 shows the characteristics of the laser drive circuit, and the relationship between the transmitted optical power, that is, the average value Pwr, and the slope efficiency S, threshold current Ith, DC bias current Ibias, and modulation current Imod of the laser is obtained as follows:

Pwr＝(Imod/2+Ibias-Ith)*S (1)

The extinction ratio refers to the ratio of the average optical power P1 of the module output "1" to the average optical power P0 of the output "0". That is, the relationship expression between the extinction ratio ER and the laser threshold current Ith, DC bias current Ibias, and modulation current Imod is:

ER＝10lg(P1/P0) (2)

ER＝10lg[(Imod+Ibias-Ith)/(Ibias-Ith)] (3)

Referring to Fig. 4, when adopting the embodiment of the present invention to work, comprise the following steps:

1. Configure whether to enable automatic debugging registers, 0 means not to enable automatic debugging, and manual debugging can be performed;

2. Configure the step size registers of DA0 and DA1, and select the step size of DA0 and DA1;

3. Configure the threshold current Ith and slope efficiency of the laser (provided by the BOSA manufacturer);

4. Configure the target values of transmit optical power Pwr and extinction ratio ER;

5. Configure the initial values of DA0 and DA1;

6. Enable automatic calculation switch;

7. Get the final values of DA0 and DA1, and turn off the automatic calculation switch, and enable it again for the next calculation.

Refer to Figure 5 for the flow chart of traditional optical eye diagram manual debugging.

Claims (1)

1. the optical module of accessible site sends an automatic Debugging circuit for light eye pattern, it is characterized in that being provided with algoritic module, Ibias current digital analog conversion module, Imod current digital analog conversion module, Ibias current monitoring module, Imod current monitoring module;

Algoritic module output connects Ibias current digital analog conversion module input and Imod current digital analog conversion module input respectively, the input of the output termination Ibias current monitoring module of Ibias current digital analog conversion module, the input of the output termination Imod current monitoring module of Imod current digital analog conversion module, the Ibias current output terminal of Ibias current monitoring module and the Imod current output terminal of Imod current monitoring module connect the driver chip input of laser respectively; Ibias current monitoring module is connected back algoritic module again with Imod current monitoring module.