Reference Clock Rate Detection for Variable Rate Transceiver Modules

In an optical/electrical transceiver, a system for determining an optical signal frequency range, the system comprising:

• a clock data recovery (CDR) unit having network interface to accept an optical receive signal having a non-predetermined data rate, a framer interface to accept an electrical reference clock signal having a non-predetermined frequency, and a phase-locked loop (PLL) including a selectable voltage controlled oscillator (VCO) to supply an electrical receive data clock via the framer interface;
• and,
• a frequency calculation module having an interface to accept the reference clock signal, the frequency calculation module determining the reference clock signal frequency, cross-referencing the determined clock signal frequency to an optical receive signal frequency, and supplying a VCO selection signal to the CDR PLL.

In an optical/electrical clock synthesizer unit (CSU), a system for determining an optical transmit signal frequency range, the system comprising:

• a clock synthesizer unit (CSU) having a framer interface to accept electrical transmit data, a PLL including a selectable VCO with a VCO output frequency frequency-locked to the reference clock and supplied as a transmit serial clock, an electrical converter to convert the electrical transmit data into an optical transmit signal, and a network interface to supply the optical transmit signal at the rate of the transmit serial clock;
• and,
• a frequency calculation module having an interface to accept a reference clock signal, the frequency calculation module determining the reference clock signal frequency, cross-referencing the determined reference clock signal frequency to an optical transmit signal frequency, and supplying a VCO selection signal to the CSU PLL.