Optical pre-amplifier apparatus and method for receiver performing gain control according to los declaration

Abstract

A receiver node includes an optical amplifier optically coupled to the input of a receiving device such as a PIN photodiode. A controller inputs received power level values from the receiver to perform gain control. The input signal of an optical receiving device, is pre-amplified by an optical amplifier such that the amplified signal is within a dynamic range of the receiving device. Upon the occurrence of a LOS (loss of signal) event, the controller sets the gain to a Home Gain value. Thus, when the signal is reestablished, a strong signal will not be over amplified and damage the receiver. Gain control is reestablished when the LOS event is over. Various methods are used to declare LOS including comparing the received power level or commanded pump power against a threshold. The LOS declaration may also be received from an external device or service channel.

Description

[0001] 1. Field of Invention[0002] The invention generally relates to optical communication receivers. The invention more particularly relates to optically pre-amplified receiver nodes.[0003] 2. Description of Related Art[0004] In conventional long-haul optical communications applications, the loss between the laser transmitter and the receiver is typically fixed or otherwise substantially invariant. Therefore, a gain block with fixed optical gain serves the purpose of ensuring that the receiver will receive a signal within the receiver's dynamic range.[0005] In some applications such as metropolitan optical ring networks, however, the loss between the laser transmitter and the receiver often changes due to changes in the span loss or due to channel upgrades. During channel upgrades, extra OADMs (optical add drop multiplexers) are added into the optical path of existing channels, therefore the loss between the transmitter and the receiver changes.[0006] Furthermore, a complete fiber...

AI Technical Summary

Benefits of technology

0088] The use of such windows is particularly advantageous in the optical signaling and reception environment. Adjusting the pump 40 power excessively may introduce noise and cause the BER (bit error rate) to rise. Any increase in the BER is unacceptable as the specifications for BER are extremely demanding (on the order of 10.sup.-15 bit errors per second being an acceptable BER). The use of windows reduces the amount of pump 40 power level changes and possible race round conditions due to minor variations in power and thereby prevents an increase in the BER.

0089] The windowing concept has other advantages for companies deplo

Problems solved by technology

Adjusting the pump 40 power excessively may introduce noise and cause the BER (bit error rate) to rise.

Any increase in the BER is unacce

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