Hong-Fu Ting

Linearization of phase-modulated analog optical links using a four-wave mixing comb source.

We present a novel method for distortion elimination in phase-modulated analog optical links. A small part of the phase modulated signal seeds a four-wave mixing comb source, which generates lightwaves with integer multiples of the phase modulation of the original signal. These lightwaves are scaled and re-combined with the original phase-modulated signal to cancel the distortion generated in the interferometric phase-to-amplitude conversion process. Experimentally, we demonstrate full cancelation of the third-order distortion of the receiver and achieve a 19-dB improvement in the links SFDR at a 1-Hz bandwidth. This approach is readily extendable to eliminate all relevant higher-order distortion products or synthesize arbitrary phase-to-amplitude transfer functions.

High-speed all-optical NAND/AND logic gates using four-wave mixing Bragg scattering.

A high-speed all-optical NAND logic gate is proposed and experimentally demonstrated using four-wave mixing Bragg scattering in highly nonlinear fiber. NAND/AND logic functions are implemented at two wavelengths by encoding logic inputs on two pumps via on-off keying. A 15.2-dB depletion of the signal is obtained for NAND operation, and time domain measurements show 10-Gb/s NAND/AND logic operations with open eye diagrams. The approach can be readily extended to higher data rates and transferred to on-chip waveguide platforms.

Linearization of phase-modulated analog links using four-wave mixing in an optical comb source

We present a high SFDR (123.7 dB) phase-modulated optical link, designed using nonlinear optical processing to eliminate third-order distortion. We also show its application to other areas of microwave photonics, specifically programmable function generation.

All-optical NAND logic gate using four-wave mixing

We demonstrate a high-speed all-optical NAND gate based on four-wave mixing Bragg scattering in highly nonlinear fiber. A 15.2-dB depletion of the signal is obtained and time domain measurements show 10-Gb/s NAND operation.

Broadband receiver-based distortion elimination in phase-modulated analog optical links using four-wave mixing

We present a method for full distortion elimination in phase-modulated analog optical links using the nonlinear optical process of four-wave mixing (FWM). Phase-modulated links consist of a laser and phase modulator in the transmitter and an interferometer (or local oscillator) and photodiode in the receiver. Phase modulation is a linear process, so distortion is introduced in the interferometric detection process. Quadrature biasing eliminates even-order distortion products, leaving only odd-order distortion. Here we introduce a method for eliminating these odd-order distortion products in the receiver. A small portion of the phase-modulated signal is tapped and combined with an unmodulated CW laser to seed a cascaded FWM comb source. This process generates an array of lightwaves with integer multiples of the signal’s phase modulation. By suitably scaling and combining these lightwaves with the original signal the overall transfer function of the interferometric receiver can be linearized (or given another tailored shape) through a Fourier synthesis approach. By combining a single lightwave from the generated comb with the original signal, we demonstrate the complete elimination of third-order distortion from the phase-modulated link leaving fifth-order distortion as the dominate source of distortion. We show a 17.6-dB SFDR improvement (1-Hz bandwidth) for a 6 GHz link operating at 5-mA total photocurrent and a 16.4-dB SFDR improvement (1-Hz bandwidth) for a 15 GHz link operating at 10-mA total photocurrent. By appropriately combining additional lightwaves from the generated comb, higher-order distortion products can be eliminated to produce an ideal linear (or custom shaped) transfer function.

Simulation and experimental demonstration of coherent OCDMA using spectral line pairing and heterodyne detection

A fully coherent optical code-division multiple access (OCDMA) scheme that combines spectral phase encoding (SPE) and spectral line pairing to generate signals through heterodyne decoding is proposed. A simple balanced receiver performs sourceless heterodyne detection, canceling speckle noise and multiple-access interference (MAI). A 16 user 100% load system transmitting at 40 Gbits is simulated, and a 4 user 50% load system transmitting at 4.25 Gbit/s is experimentally demonstrated for the first time.

Experimental demonstration of coherent OCDMA using heterodyne detection

We present the first experimental demonstration of a practical, fully coherent, optical code division multiple access (OCDMA) scheme that can fully suppress multiple access interference (MAI) and speckle noise without phase locking or thresholding and gating. The scheme is sourced from an optical comb generator and uses spectral phase encoding and a heterodyne receiver with balanced detection. Here we present results for a four-user configuration at 50% load. At 4.5 Gbits/s per user, the system achieves a signal to MAI ratio of 648 at a bit error rate of 10(-7).

Wavelength multicasting through four-wave mixing with an optical comb source

Based on four-wave mixing (FWM) with an optical comb source (OCS), we experimentally demonstrate 26-way or 15-way wavelength multicasting of 10-Gb/s differential phase-shift keying (DPSK) data in a highly-nonlinear fiber (HNLF) or a silicon waveguide, respectively. The OCS provides multiple spectrally equidistant pump waves leading to a multitude of FWM products after mixing with the signal. We achieve error-free operation with power penalties less than 5.7 dB for the HNLF and 4.2 dB for the silicon waveguide, respectively.