Ivan Glesk

A terahertz optical asymmetric demultiplexer (TOAD)

A device capable of demultiplexing Tb/s pulse trains that requires less than 1 pJ of switching energy and can be integrated on a chip is presented. The device consists of an optical nonlinear element asymmetrically placed in a short fiber loop. Its switching time is determined by the off-center position of the nonlinear element within the loop, and therefore it can use the strong, slow optical nonlinearities found in semiconductors, which all other fast demultiplexers seek to avoid. The switchs operation at 50 Gb/s is demonstrated, using 600-fJ control pulses.<<ETX>>

A widely tunable narrow linewidth semiconductor fiber ring laser

We have demonstrated a novel approach to obtain a 0.1-nm line width laser with 38-dB sidemode suppression by utilizing a 1.3-/spl mu/m semiconductor optical amplifier in a fiber unidirectional ring that consists of a linear polarizer and polarization controllers. The laser has a low-threshold current of 22.5 mA as well as a wide tuning range of 28 nm. The new approach is applicable to the 1.55-/spl mu/m region as well. It is expected that nanosecond wavelength tuning speed is feasible using this approach in conjunction with fast electrooptic polarization controllers, short cavities and low-cavity losses.

All-optical data format conversion between RZ and NRZ based on a Mach-Zehnder interferometric wavelength converter

We demonstrate all-optical conversion between two different data formats: return-to-zero (RZ) and nonreturn-to-zero (NRZ) using a Mach-Zehnder interferometric wavelength converter. For RZ-to-NRZ conversion, a duplication scheme is demonstrated to reduce the ripples caused by the carrier recovery of the semiconductor optical amplifier. The relationship between the ripple-to-signal ratio and the number of pulse duplications is numerically analyzed. For the NRZ-to-RZ conversion, the wavelength converter also shows high performance. The converted RZ signal has a negative power penalty to the NRZ signal due to the change of the data format.

Performance of a 50 Gbit/s optical time domain multiplexed system using a terahertz optical asymmetric demultiplexer

Bit error rate measurements were performed on a 50 Gbit/s optical time domain multiplexed system which utilized the newly developed terahertz optical asymmetric demultiplexer (TOAD) device as the front end of a receiver. Bit error rates of less than 10/sup /spl minus/9/ were measured when 800 fj control pulses were used to gate the demultiplexer. These measurements, which were made on a 50 Gbit/s peak line-rate train, also quantified the tolerance of the TOAD to signal-control pulse jitter.<<ETX>>

Comparison of Sagnac and Mach-Zehnder ultrafast all-optical interferometric switches based on a semiconductor resonant optical nonlinearity

We present a theoretical analysis of recently demonstrated ultrafast all-optical interferometric switching devices (based on Sagnac and Mach-Zehnder interferometers) that use a large optical nonlinearity in a resonant regime. These devices achieve ~10-ps switching windows and do not require high-energy optical control pulses. We theoretically analyze and compare one Sagnac and two Mach-Zehnder switching configurations.

Experimental demonstration and scalability analysis of a four-node 102-Gchip/s fast frequency-hopping time-spreading optical CDMA network

We present experimental and simulation results from a 102-Gchips/s incoherent wavelength-hopping time-spreading optical code-division multiple-access testbed, utilizing four 50-GHz ITU grid wavelengths. Error-free operation of four users is obtained with an effective power penalty /spl sim/0.5 dB. Simulation studies show scalability to >10 users with an effective power penalty of /spl sim/4 dB. The simulation study of the impact of asynchronous access on the performance allows for a complete network design from an engineering viewpoint.

A novel fast optical switch based on two cascaded Terahertz Optical Asymmetric Demultiplexers (TOAD)

A novel optical switch based on cascading two terahertz optical asymmetric demultiplexers (TOAD) is presented. By utilizing the sharp edge of the asymmetric TOAD switching window profile, two TOAD switching windows are overlapped to produce a narrower aggregate switching window, not limited by the pulse propagation time in the SOA of the TOAD. Simulations of the cascaded TOAD switching window show relatively constant window amplitude for different window sizes. Experimental results on cascading two TOADs, each with a switching window of 8ps, but with the SOA on opposite sides of the fiber loop, show a minimum switching window of 2.7ps.

Unbalanced TOAD for optical data and clock separation in self-clocked transparent OTDM networks

We simulate and demonstrate a single-beam intensity-thresholding all-optical switch by modifying a terahertz optical asymmetric demultiplexer (TOAD) with an uneven power splitting in the loop. An optimized set of parameters used in the demonstration is found from the simulations considering the saturation of the semiconductor optical amplifier. With 8.7-dB input clock-to-data ratio, the clock-to-data ratio can be suppressed down to -7.4 dB at the reflected (data) port. An amplified output with 3.0 dB clock-to-data ratio improvement was achieved in the transmitted (clock) port at a low switching energy of 150 fJ. The device can be used for clock recovery in self-clocked optical networks.

ASYMMETRIC OPTICAL LOOP MIRROR : ANALYSIS OF AN ALL-OPTICAL SWITCH

We present an analysis of the optical loop mirror in which a nonlinear optical element is asymmetrically placed in the loop. This analysis provides a general framework for the operation of a recently invented ultrafast all-optical switch known as the terahertz optical asymmetric demultiplexer. We show that a loop with small asymmetry, such as that used in the terahertz optical asymmetric demultiplexer, permits low-power ultrafast all-optical sampling and demultiplexing to be performed with a relatively slow optical nonlinearity. The size of the loop is completely irrelevant to switch operation as long as the required degree of asymmetry is accommodated. This is therefore the first low-power ultrafast all-optical switch that can be integrated on a single substrate.

Scalable Asynchronous Incoherent Optical CDMA [invited]

We present and review several aspects of incoherent optical code-division multiple access (OCDMA), focusing on the flexible bandwidth allocation and its potential for future optical networks. We briefly present the various OCDMA approaches, coherent and incoherent, before focusing on the later and more specifically temporal 1D and 2D wavelength-hopping time spreading. We then concentrate on the properties specific to such schemes allowing for its increased scalability and flexibility. The main coding properties are reviewed, and the multicode property for increased performance and security is described. Several subsystems are presented to allow the compatibility of OCDMA on multihop networks where the properties of OCDMA would allow shifting some management functions down to the physical layer creating an optical layer with enhanced functionalities.