Simultaneous Signal Amplification and Clock Distribution Employing Backward Raman Pump Over an Optical Fiber for Applications Such as Square Kilometer Array
Abstract
For the first time to our knowledge, we experimentally demonstrate a clock signal transmission using a counter-propagating Raman pump as a transmitter and concurrently utilize the same pump to amplify a data signal. A 1548nm vertical cavity surface emitting laser (VCSEL) was modulated with a pseudorandom bit sequence (27−1) and coupled into an optical fiber. A 1448nm Raman pump in the backward scheme was also modulated with a 10kHz clock and used to boost the VCSEL data signal so as to improve the reach of the transmission. Clock distribution in a telescope network such as the Square Kilometre Array (SKA) is essential for the proper operation of the digitizers as well as dish synchronization. In the SKA phase 1, long transmissions involving baselines extending up to 100km may need amplification. We propose the use of counter-Raman configuration to amplify the signal carrying received astronomical data while transmitting a clock to the receptors. This is a cost-effective bi-directional transmission suited for telescope network applications.
