E. Gamper

Multimode interference couplers for the conversion and combining of zero- and first-order modes

Optical waveguide mode-combiners for fundamental and first-order modes, based on multimode interference (MMI) couplers are presented. These devices convert a fundamental mode into a transversal first-order mode and combine it in lossless fashion with a second fundamental mode. They can separate zero- and first-order modes in a common waveguide and allow the splitting and combining of zero- and first-order modes with nonuniform power splitting ratios. Realizations in InGaAsP-InP are demonstrated. These new components have successfully been integrated into all-optical switches and were found to have advantageous characteristics in all-optical devices.

All-optical space switches with gain and principally ideal extinction ratios

Asymmetric Mach-Zehnder interferometer (MZI) configurations are proposed to build all-optical space switches with gain and principally ideal extinction ratios. Actually, three asymmetries in MZI configurations with semiconductor optical amplifiers (SOAs) on their arms are discussed. The asymmetries in the all-optical switches are necessary to overcome the extinction ratio limitations that are due to the disturbing gain changes that arise when control signals are introduced into the SOAs to induce the necessary refractive index change for switching. Starting from a generic MZI configuration with SOAs on the arms, a description in terms of transmission matrices is used and applied to identify 1/spl times/2 and 2/spl times/2 all-optical switch configurations with high on-state transmissions and close to ideally large extinction ratios. The theoretical predictions are verified and found to be in excellent agreement with experiments for a switch with symmetric MZI splitters in a monolithically integrated InP waveguide version that allows operation with equally or unequally biased SOAs.

All-optical demultiplexing of 80 to 10 Gb/s signals with monolithic integrated high-performance Mach-Zehnder interferometer

A novel high-performance monolithic integrated Mach-Zehnder interferometer with semiconductor optical amplifiers (SOAs) in its arms has been realized and 80-Gb/s all-optical demultiplexing demonstrated. Penalty-free operation for 40-10 Gb/s demultiplexing has also been achieved. Dynamic range with respect to the input signal power for error-free operation at 40 Gb/s is more than 17 dB and fiber-to-fiber loss less than 2 dB. A theoretical model which takes into consideration amplifier gain dynamics and pulse propagation describes the demultiplexing experiments and predicts the device performances also at higher bit rates.

All-optical Mach-Zehnder interferometer wavelength converters and switches with integrated data- and control-signal separation scheme

All-optical Mach-Zehnder interferometer (MZI) wavelength converters and switches with monolithically integrated data- and control-signal separation schemes are reported. Two schemes to separate the data from the strong control signals are discussed. A first dual-order mode configuration uses modes of different symmetry for the data and control signals. A second configuration uses additional MZIs to separate the two signals. The control-signal separation permits to operate the devices with copropagating data and control signal without distortion of the control signal in the data-signal output. Copropagative operation allows for shorter switching windows compared to the counterpropagative operation. Further, this concept enables cascading of several devices since the control signal is filtered out and does not disturb the signal processing in a next cascade of devices. The all-optical switches are characterized under static and dynamic 10 GHz conditions.

Ultrafast switching dynamics of Mach-Zehnder interferometer switches

We present results of cross-gain and cross-phase modulation experiments on InGaAsP-based semiconductor optical amplifiers and Mach-Zehnder interferometer (MZI) switches. For 150-fs input pulses, we observe strong spectral and pulse shape distortions of the signal pulse, especially in the pulse overlap regime. These pulse deteriorations are induced by subpicosecond gain and refractive index nonlinearities. In consequence, the ON-OFF ratio of the MZI switch is drastically reduced for subpicosecond switching windows. In the copropagation arrangement, the switching window with maximum transmission is shown to be limited to about 1.5 ps.

All-optical regenerative OTDM add-drop multiplexing at 40 Gb/s using monolithic InP Mach-Zehnder interferometer

We present a novel method for all-optical add-drop multiplexing having regenerative capability for 40-Gb/s optical time-division multiplexed (OTDM) data using a semiconductor optical amplifier (SOA) based, monolithic Mach-Zehnder interferometer (MZI). Simultaneous dropping of one 10-Gb/s channel out of 10-Gb/s OTDM data and perfect clearing of the corresponding time slot in the remaining 3/spl times/10 Gb/s data stream is demonstrated. Bit-error-rate measurements show a low penalty of 2 dB for each 10 Gb/s channel. No extra penalty was observed introducing a 10-Gb/s add channel through the device into the cleared time slot.

40-Gb/s OTDM to 4 x 10 Gb/s WDM conversion in monolithic InP Mach-Zehnder interferometer module

Transformation of high bit-rate optical time-domain multiplexed (OTDM) signals into a multitude of lower bit-rate wavelength-division-multiplexed (WDM) channels is demonstrated by means of a single monolithically integrated indium phosphide Mach-Zehnder interferometer with semiconductor optical amplifiers in its arms. Full demultiplexing of 10-Gb/s OTDM signals into 4/spl times/10-Gb/s WDM channels is demonstrated. Bit-error-rate penalties are below 1.5 dB for polarization independent signal conversion throughout the 1.55-/spl mu/m wavelength range.

Bit error rate assessment of 80 Gb/s all-optical demultiplexing by a monolithically integrated Mach-Zehnder interferometer with semiconductor optical amplifiers

Error free 80-10 Gb/s all-optical demultiplexing is demonstrated using a monolithically integrated Mach-Zehnder interferometer (MZI) with SOAs. At 40 Gbit/s add-drop multiplexing, penalty-free demultiplexing and a large (>17 dB) dynamic range is demonstrated.

All-optical sampling with a monolithically integrated Mach-Zehnder interferometer gate.

An all-optical sampler consisting of a polarization-independent monolithic Mach-Zehnder interferometer with integrated semiconductor optical amplifiers and a temporal resolution of 1 ps is presented. As an example, a simple 320-Gbit/s pattern has been successfully sampled, demonstrating the functionality of this scheme for high-bit-rate waveform characterizations in light-wave systems.

Polarization independent optical phase conjugation with pump-signal filtering in a monolithically integrated Mach-Zehnder interferometer semiconductor optical amplifier configuration

Demonstration of polarization independent optical phase conjugation by four-wave mixing in a monolithic Mach-Zehnder interferometric semiconductor optical amplifier (SOA) configuration. An integrated filtering mechanism for the pump-signal enhances the conjugate-to-pump ratio by 15 dB compared to the single SOA case.