Chun He

MEMS optical switches with guaranteed switching status

Techniques for controlling and monitoring MEMS optical switches are disclosed. In one embodiment, an electronic feedback loop is employed to determine a control signal to a MEMS switch actuator in accordance with an instruction. The control signal is so determined in such a way that the switching statuses are maximally guaranteed. To generate an appropriate control signal, AC or DC impedances of the MEMS switch are detected and used to configure the control signal to drive the switch. When it is detected that the impedance changes do not meet respective thresholds, the control signal is adjusted. In the case that the stiction happens, the switch actuator is overcharged, discharged and repeatedly applied for a limited time to overcome the stiction.

Functionally integrated reconfigurable optical add/drop module

Reconfigurable Add/drop Multiplexer (ROADM) is a broad definition of a functionally reconfigurable filtering device for dynamic networking. We focus on a class of ROADM architecture that allows scalability of wavelength channels, add/drop port counts as well as functional capability of integrating variable attenuation and monitoring elements. We demonstrate the proposed concepts of integrating a ROADM with a variable optical attenuator and a performance monitor array.

Techniques for reconfigurable optical add/drop multiplexer

Reconfigurable optical add/drop multiplexer (ROADM) is a next generation critical component that facilitates the network system evolution from a point-to-point transmission-oriented structure to an all-optical, wavelength-flexible, dynamic network. ROADM enables flexible removal and insertion of WDM channels at either a head-end or intermediate nodes-making it possible for true network provisioning and reconfiguration. We will review the pros and cons of each of the techniques for tunable OADM, from their operating principles to their practical implementations with special emphasis on two approaches: a TTF based three-port tunable filter as a basic one-channel tunable add/drop multipexer and a full-scale, MEMS mirror array based 80-channel reconfigurable OADM subsystem. Comparative laboratory experimental results with theoretical calculations are presented.

Nonlinearity measurements of PIN photodiode based ROSA for FTTX applications

We have designed and fabricated PIN photodiode based ROSA used for FTTX applications. The critical nonlinearity parameters of Inter-modulation Distortion (IMD) were measured by two RF modulated light sources near 1550nm wavelength channels. A cost effective measuring system with narrow pass band filter was set up and some procedures were utilized for determining the low level signals of IMD. Obtained test results were used in real time to guide packaging process to achieve best receiver performance.