Fiber-optic signal processor with applications to matrix-vector multiplication and lattice filtering

Polynomial-based optical true-time delay devices with microelectromechanical mirror arrays

We previously reported optical true-time delay devices, based on the White cell, to support phased-array radars. In particular, we demonstrated a quadratic device, in which the number of delays obtainable was proportional to the square of the number of times the light beam bounced in the cell. Here we consider the possibilities when a microelectromechanical (MEM) tip/tilt mirror array with multiple stable states is used. We present and compare designs for quadratic, quartic, and octic cells using MEM mirror arrays with two, three, and five micro-mirror tilt angles. An octic cell with a three-state MEM can produce 6,339 different delays in just 17 bounces.

Adaptive optoelectronic signal processor with metal-semiconductor-metal photodetector arrays

Optoelectronic structures utilizing switched fiber delays and switched metal-semiconductor-metal photodetectors for signal processing over a 1.25-GHz bandwidth are presented. Fully tunable finite-impulse-response and infinite-impulse-response structures were synthesized with internal compensation for bias dependency of photodetectors. The application of such filter structures to the equalization of modal dispersion in a multimode fiber is also described.

Integrated acoustooptic circuits and applications

The recent development of titanium-indiffusion proton-exchange (TIPE) microlenses and lens arrays has made possible the construction of a variety of single- and multichannel integrated acoustooptic (AO) and acoustooptic-electrooptic (EO) circuits in LiNbO(3) channel-planar waveguides 0.1x1.0x2.0 cm(3) in size. These hybrid AO and AO-EO circuits can be fabricated through compatible and well-established technologies. The most recent realization of ion-milled microlenses and lens arrays together with the recent development of gigahertz AO Bragg modulators and EO Bragg modulator arrays have also paved the way for construction of similar but monolithic AO and AO-EO GaAs/GaAlAs waveguides of comparable size. Both types of integrated AO and AO-EO circuits suggest versatile applications in communications signal processing, and computing. Efficient and simultaneous excitation of the channel waveguide array using an ion-milled planar microlens array has facilitated the demonstration of some of these applications.

Optical implementation of the Hopfield neural network using multiple fiber nets

Associative memory based on the Hopfield model utilizing interconnections by multiple optical fiber nets is proposed and demonstrated experimentally. The coupling ratio from fiber to fiber represents the synaptic weight of the connection between units. The remarkable feature of the optical fiber neural networks is that global connections between 2-D units can be easily achieved, resulting in simultaneous multiplication of the weight matrix and input vector. In the experiment, multiple fiber nets having 25(2) connections for 5 x 5 binary patterns are prepared, and three patterns are stored and successfully retrieved.

High-packing-density multichannel integrated-optic modules in LiNbO(3) for a programmable correlation of binary sequences

Two 10-channel integrated-optic device modules have been constructed and tested. The architecture common to both modules consists of a LiNbO(3) composite waveguide 1.0 cm x 2.0 cm in size in which a channel-waveguide array, a planar waveguide, a linear microlens array, an electro-optic Bragg modulator array or an acousto-optic and electro-optic Bragg modulator array, and a large-aperture lens are integrated. A novel scheme that employs a linear ionmilled planar microlens array was devised to excite the entire channel-waveguide array simultaneously, and thus greatly facilitate testing and application of the two device modules. The performance characteristics obtained in programmable correlation of binary sequences are also presented.

Programmable fiber/integrated-optics bipolar tap

A programmable bipolar tap implementation is described. The proposed scheme utilizes fiber and integrated-optics technology in conjunction with twos complement number representation and digital multiplication by an analog convolution algorithm. Simple experimental verification of the scheme is presented.

Integrated electrooptic Bragg modulator modules for matrix-vector and matrix-matrix multiplications

Successful fabrication of high performance microlenses and microlens arrays using the titanium-indiffusion and proton-exchange technique has enabled realization of a variety of integrated electrooptic Bragg modulator modules in the LiNbO(3) channel-planar composite waveguides of 0.2- x 1.0- x 1.8-cm(3) substrate size. These integrated optic device modules have been utilized successfully to perform matrix-vector and matrix-matrix multiplications. Through the channel-waveguide and the linear microlens arrays, the very large channel capacities that are inherent in the diode laser and the optical fiber as well as the photodotcctor arrays may be conveniently exploited. Consequently, such integrated optic device modules should facilitate realization of multichannel optical computing as well as communication and rf signal processing systems.

Fiber-optic matrix multiplier using a two-dimensional systolic-array architecture

An optical matrix multiplier based on a two-dimensional systolic-array architecture is described, exploiting the parallelism offered by optical methods. Experimental verification of multiplier performance is presented. A technique for multiple matrix multiplications is suggested.

Electrooptical processing of signal transforms

New architectures are discussed for the implementation of signal transforms using new techniques in optical computing and signal processing. These architectures are based on the factorization of any discrete trigonometric transform matrix into a simple preprocessing matrix followed by a matrix consisting of the direct sum of circular convolutions.

Laser phase noise effects in fiber-optic signal processors with recirculating loops

The power spectrum of the optical intensity at the output of a single-mode-fiber recirculating delay line driven by a multimode semiconductor laser is shown to exhibit a spectral structure with notches at zero frequency as well as at other multiples of 1/(loop delay). A theoretical model based on laser phase noise is suggested to explain the experimental data.