Sampling-based balanced detection system

摘要

A two-gate sampling system has been designed to perform sampled balanced detection of one or more input signal pairs. The present invention performs simultaneous sampling of both signals in each signal pair followed by digitization and combination of the sample pairs using software. By first sampling the signals and then combining the sampled into the corresponding balanced detected signal it is possible to avoid the bandwidth limitations and impedance problems introduced by traditional balanced detectors and electrical oscilloscopes. In particular, for optical sampling gates very high bandwidth sampling gates can be designed without any impedance issues and hence almost perfect balanced detection reconstruction can be performed for very high speed signals. Balanced detection is becoming more and more important as the new phase modulated optical data signals are introduced to the market, such as e.g. PSK, DPSK, QPSK and DQPSK. The present invention is well suited for analysis of these new types of signals.

主权项

1. A sampling arrangement for performing balanced detection of a pair of input optical data signals from an original phase-encoded modulated optical data signal, the sampling arrangement comprising
a delay interferometer responsive to the original phase-encoded modulated optical signal and providing a pair of apportioned input optical data signals at a common point of the delay interferometer output, the input optical data signals consisting of a constructive-interference optical signal and a destructive-interference optical signal: at least one pair of sampling gates, a first sampling gate of said pair responsive to the constructive-interference optical signal of the pair of input optical data signals and a second sampling gate of said pair responsive to the destructive-interference optical signal of the pair of input optical data signals, each sampling gate opened and closed by a control signal applied as separate input thereto for creating as an output a stream of optical samples representative of the respective input data signal applied thereto; a strobe source for generating a sampling signal applied as the control signal input to each sampling gate, the sampling signal operable to provide sampling by controlling the at least one pair of sampling gates to synchronously open and close at a predetermined sampling frequency fs; at least one adjustable delay means associated with said at least one pair of sampling gates, said at least one adjustable delay means configured to ensure that said at least one pair of sampling gates generates samples originating from the same point in time in said original data signal as arriving at the common point; and at least one A/D converter to convert a detected version of the streams of samples into a digital representation thereof; a software processing and signal visualization system configured to provide a visual representation of the waveform of said pair of input data signals.