OPTICAL COMMUNICATION MODULES

摘要

A 10 Gbit/s XFP transceiver module comprises a receive optical sub-assembly (ROSA) for receiving a modulated optical signal transmitted along an optical fibre, and a transmit optical sub-assembly (TOSA) for modulating an optical output signal from a laser with the data signal to produce a modulated optical signal to be transmitted along an optical fibre to a remote receiver. The transceiver module also incorporates a receiver CDR circuit for receiving the output signal from the ROSA, and a transmitter CDR circuit for transmitting a conditioned data input signal to the TOSA. Each of the CDR circuits incorporates a limiting input amplifier 10 (LIA), a retiming circuit 11, and a phase detector 12 for supplying an output signal to a voltage controlled oscillator 15 (VCO) by way of an amplifier 13 and a loop filter 14' comprising two possible control paths 20, 21. The control path 20 incorporates a resistor R1, a switching transistor Q1A and a capacitor C2 whereas the control path 21 incorporates a resistor R2, a switching transistor Q1B and a capacitor C3. Furthermore separate control lines 23 and 24 are coupled to the switching transistors Q1A and Q1B to effect switching so that either the control path 20 only is activated to provide a first control status, or the control path 21 only is activated to provide a second control status, or both the control paths 20 and 21 are activated to provide a third control status. Any one of the three possible control statuses may be selected to provide a required loop bandwidth so that jitter can be optimised over a range of possible data transmission rates.