Method for judging optimal working voltage of APD (Avalanche Photo Diode) of 10G EPON (Ethernet Passive Optical Network)

Abstract

The invention discloses a method for judging the optimal working voltage of an APD (Avalanche Photo Diode) of a 10G EPON (Ethernet Passive Optical Network). The method comprises the following steps that: S1: according to the testing data of a BOSA or RSSI (Received Signal Strength Indicator) under a dark condition, obtaining the reverse breakdown voltage Vbr of the APD; S2: setting initial value working bias voltage, selecting fixed input light power, according to preset time of duration, testing a current error code rate or an error code number, then, carrying out stepping increasing on the working bias voltage by a set stepping value to repeatedly test at least three points until the error code rate or the error code number is increased; S3: taking the working bias voltage x and the error code rate y to solve a quadratic equation of one unknown y=ax2+bx+c to obtain three coefficients a, b and c; S4: according to the three obtained coefficients a, b and c, calculating an extreme valuex=-b / 2a, and obtaining a corresponding APD DAC (Digital to Analog Convertor); and S5: utilizing the APD DAC value to carry out sensitivity testing, if the sensitivity testing is qualified, carrying out subtraction and translation on the APD DAC of the current temperature and an APD DAC LUK table to be updated into the APD DAC LUK, and if the sensitivity testing is unqualified, failing.

Description

technical field [0001] The invention relates to the field of photodiodes, in particular to a method for judging the optimum working voltage of an avalanche photodiode APD of 10G EPON. Background technique [0002] APD improves performance on the basis of PIN photodiodes. Compared with PIN photodiodes, a layer of P-type material is added after the I layer. When the voltage is low, most of the voltage falls in the PN+ region. When the voltage increases, the width of the depletion region increases until the voltage on the PN+ junction is lower than the avalanche breakdown voltage by 5% to 10%. The I layer is the light absorption region, where photons generate photocurrent, and the PN+ region is the avalanche region. After the photocurrent enters, it is impacted and ionized under the action of a high electric field to generate secondary hole-electron pairs, and the secondary holes may collide and ionize again. This may generate dozens or hundreds of new hole-electron pairs, the...

AI Technical Summary

Problems solved by technology

[0003] The structure of APD results in higher sensitivity than PIN photodiodes, but the circuit is also more complex and requires additional high-voltage drive

Generally, APD has an optimal working voltage. If the multiplication factor M is smaller than this working voltage, the sensitivity will decrease; if it is higher than this working voltage, the multiplication factor will become larger and the noise will also be amplified, the signal-to-noise ratio will be lower, and the sensitivity will also decrease.

Usually, the operating voltage is set according to experience, such as less than the reverse breakdown voltage of 3V or 0.9 times the reverse breakdown voltage, but in special cases it is necessary to find the best sensitivity point, but there is a certain deviation between the empirical value and the optimal value, which cannot be used as best working voltage

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