A fiber optic lattice filter having a transfer function wherein the poles and zeros are adjustable independently of each other. The filter comprises a cascaded configuration of recursive (100) and non-recursive (102) fiber optic lattice filters. In one preferred embodiment, an all-pass fiber optic filter is formed by cascading all-pole and all-zero lattice filters, and by processing the resulting filtered output signal in a subtractive detection system (104). This detection system produces a signal which represents the difference between two signal outputs provided by the all-zero filter section, and which is adjustable in magnitude, thereby providing an overall filtering function which is capable of handling both positive and negative valued input signals.
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