Light control automatic gain control circuit applied on cable television network optical receiver

Abstract

The invention relates to an optically-controlled automatic gain control circuit applied to an optical receiver of cable television network, which comprises two offset networks, a photoelectric detector and a variable attenuator. The photoelectric detector is grounded and connected with a power source via the two offset networks. The output terminal of the photoelectric detector is connected with an optical power detecting circuit, a logarithmic circuit, a phase inverting circuit, an exponential circuit, a phase proportion adjusting circuit and an adding circuit in sequence, and then is connected with the variable attenuator, thereby achieving the automatic gain control (AGC). The circuit is implemented by use of the pure analog hardware, and can control the input light power in the range above 10dB, namely, the radio-frequency output level in the range above 20dB.

Description

technical field [0001] The invention relates to a circuit of an optical receiver applied to a cable television network, and more specifically relates to an optical control automatic gain control circuit of an optical receiver. Background technique [0002] Whether it is the traditional fiber-coaxial hybrid network (HFC), or the FTTC (fiber-to-the-curb), FTTB (fiber-to-the-building) and FTTH (fiber-to-the-home) networks that operators are gradually promoting, signal transmission requires large dynamic range. Usually, for network design, it is hoped that the user end can receive a stable power level, therefore, the network design needs to carry out level control, no matter it is manual or automatic. [0003] For the traditional HFC network, the receiving dynamic range of the general optical node is designed to be small when the network is designed, and it is generally designed to receive at -1dBm, and the number of users covered by a single optical node on the optical distrib...

AI Technical Summary

Problems solved by technology

The disadvantage of this method is that it needs to perform analog-to-digital and digital-to-analog conversion. The frequency of the crystal oscillator used in the single-chip microcomputer is generally a few MHz to a dozen MHz, and it is a square wave with a wide harmonic spectrum, ranging from tens of MHz to hundreds of MHz. MHz, it is very prone to radiated interference, so it is a very troublesome source of interference

AGC with wide control range and high control precision requires high control precision of A / D, and if digital control produces interference, it will be very difficult to eliminate

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