External sudden automatic optical-power control circuit

Abstract

The invention provides an external sudden automatic optical-power control circuit comprising a sampling resistor, a sudden sampling retaining circuit, a buffer circuit, a sampling compensation circuit and a microcontroller, wherein the microcontroller is provided with an A / D conversion end and at least one D / A conversion end; a laser bias current control signal is output by one D / A conversion end; one end of the sampling resistor is earthed, and the other end is connected with the input end of the sampling retaining circuit and the anode of the backlight diode of the laser; the output end of the sudden sampling retaining circuit is connected with the input end of the buffer circuit; the output end of the buffer circuit is connected with the A / D conversion end of the microcontroller; the sampling compensation circuit is connected between the microcontroller and the sudden sampling retaining circuit; and a BEN synchronizing signal acts on the sudden sampling retaining circuit and the sampling compensation circuit. In the external sudden automatic optical-power control circuit, an ONU (optical network unit) module has better stability and circuit expansibility for optical power and extinction ratio under the sudden working condition.

Description

technical field [0001] The invention relates to an automatic optical power control circuit of a laser driver circuit (Auto Power Control, APC for short) used for a Gigabit-Capable Passive Optical Network Unit (GPON ONU for short) of a Gigabit-Capable Passive Optical Network Unit (GPON ONU). In particular, it relates to an external burst automatic optical power control circuit. Background technique [0002] Optical fiber access has gradually become the first choice for access networks worldwide, and Passive Optical Network (PON) technology has become the most cost-effective technical solution in optical fiber access networks. Passive optical network technology adopts time division multiplexing (Time Division Multiplexer, TDM) uplink and broadcast downlink transmission mode to make the broadband application rate of optical network higher. The central office (Optical Line Termianl, OLT for short) downlinks the control signal and uploads the optical signal to the OLT within the...

AI Technical Summary

Problems solved by technology

However, the built-in burst APC circuit has the following disadvantages: 1. When the ONU optical module of this type of integrated chip IC solution is working, if the packet interval is long (greater than 2s), when the next burst packet arrives, the module will emit light abnormally, and the performance Because it takes a period of time to re-establish the "1" level and "0" level of the optical signal, it is not allowed in normal optical transmission, which will cause data loss. The definition of the APC circuit is different, and the problem of burst time in special occasions is not fully considered, and the sampling of the backlight current Im generated by the backlight diode PD cannot be maintained for a long time, resulting in unstable optical power; 2. In actual transmission, every When the burst control signals received by each ONU optical module are different, the packet length and packet interval are quite different. The short packet length can reach less than 200ns, and the long packet length can be more than 100us. The extinction ratio of the module will become smaller than that of the long package length, up to 3~4dB. Such a large extinction ratio fluctuation is obviously undesirable, which is not good for the local end OLT, resulting in this The main reason for the phenomenon is that the bandwidth problem of the backlight diode PD itself affects the establishment time of the backlight current Im, resulting in low precision; 3. The scalability of the circuit is not good, due to the limitation of the existing integrated IC solution, resulting in a new ONU optical module Difficult to upgrade

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