Abstract: An optical analog-to-digital converter (10) which fully operates in the optical domain and utilizes an upward-folding successive approximation approach for conversion. The converter (10) includes a plurality of optical stages (14, 16, 18) where each stage (14, 16, 18) generates a digital bit. Each stage (14, 16, 18) includes an optical threshold switch (30, 56, 78) that sets the bit high when the switch (30, 56, 78) is closed. When a sample amplitude of the analog signal is compared to a threshold value and found to exceed the threshold value, the bit is set to "high" and the sample is passed directly onto the next stage (14, 16, 18). If the sample amplitude is found to be less than the threshold value, the bit is set to "low" and an intensity equal to the maximum signal intensity minus the threshold intensity is added to the sample amplitude. Each successive stage (14, 16, 18) compares the normalized signal sample to thresholds growing closer and closer to the maximum signal intensity.

Abstract: A frequency modulation-based optical analog-to-digital converter utilizes a downward-folding, successive approximation approach. A series of stages is utilized to generate bits in the digital signal. In each stage, complementary low and high bandpass filters collectively cover a bandpass frequency range from a low frequency to a high frequency. The high frequency filtered signal from the high bandpass filter is observed to obtain a bit in the digital word. By performing the folding operations in the frequency domain, the converter avoids the difficult task of optical power subtraction, relying instead on frequency down-conversions. The high frequency filtered signal passed by the high bandpass filter is then downconverted and added to the low pass filter signal to generate a modulated signal for the next stage.

Abstract: An optical inverter (10) that uses a saturable absorber (28) to distinguish between a logical one and a logical zero. A low power laser (18) generates an optical beam that is split into a first beam that propagates among a first beam path (24) and a second beam that propagates along a second beam path (26). The saturable absorber (28) is an optical switch that is positioned in the first beam path (24), and is switched from an opaque mode to a transparent mode when it receives an optical input signal. The first beam and the second beam are recombined as an optical output beam in an optical combiner (30). The first beam path (24) and the second beam path (26) have a length relative to each other such that the first and second beams are 180.degree. out of phase when they reach the optical combiner (30). Therefore, if the saturable absorber (28) is switched to the transparent mode, the first and second beams combine destructively and the optical output beam is dark, or a logical zero.

Abstract: A splitterless optical broadcast switch (110) for routing a plurality of optical carrier signals. The splitterless optical broadcast switch (110) includes an optical source (112) for generating a plurality of unmodulated optical carrier signals. A first stage routing module (114) routes the plurality of unmodulated optical carrier signals. A modulating module (116) receives a plurality of RF input signals and modulates each of the RF input signals onto any number of the unmodulated optical carrier signals to generate a plurality of modulated optical carrier signals. A second stage routing module (118) routes the plurality of modulated optical carrier signals complimentary to the first stage routing module (114). An output module (120) receives the plurality of modulated optical carrier signals such that the optical output from the optical source (112) is paired to a complimentary optical input of the output module (120).