Reinald Gerhardt

40-channel ultra-low-power compact PLC-based ROADM subsystem

We review the main ROADM subsystem technologies, and propose a 40-channel PLC-based ROADM subsystem that exhibits ultra-low power consumption and compact size, while meeting the requirements for high optical performance, high reliability, and low cost.

Hybrid-integrated optical isolators and circulators

Magneto-optics is an area that is uniquely enabling for the production of nonreciprocal components such as optical isolators and circulators. The concepts behind the nonreciprocity include nonreciprocal polarization rotation (Faraday rotation) and nonreciprocal phase shift. A magneto- optic material that is magnetized in the direction of propagation of light acts as a Faraday rotator. An asymmetric magneto-optic waveguide that is magnetized perpendicular to the propagation direction acts as a nonreciprocal phase shifter. Both effects can be utilized to realize nonreciprocal devices. Today, commercial isolators and circulators are strictly bulk components, and as such they constitute the only type of optical component that is not available in integrated form. However, the technology for integrated nonreciprocal devices has been maturing and is expected to have a considerable impact in the communication industry by enabling the integration of complete optical subsystems. We report on the development of integrated optical isolators and circulators that consist of polymer-based planar interferometers with inserted thin films of cerium-substituted Yttrium Iron Garnet (Ce-YIG) for efficient Faraday rotation, and thin films of LiNbO3 for wave-retarders that enable polarization-independent operation.

Metro ring node module based on polymeric planar lightwave circuits

We describe a 4-channel metro ring node module that performs add/drop, protection switching, and power equalization functionalities on a single chip. The worst-case insertion loss is 1.25 dB.

The integration of silica and polymer waveguide devices for ROADM applications

We report on our efforts to integrate silica and polymer waveguide devices, such as arrayed waveguide gratings (AWGs), tunable lenses, optical switches, variable optical attenuators (VOAs), power taps. In particular, the realizations of various optical add/drop multiplexers and tunable dispersion compensators are discussed. The integration techniques, the design architectures and the corresponding optical performances are presented.

Photonic integrated circuits based on silica and polymer PLC

Various methods of hybrid integration of photonic circuits are discussed focusing on merits and challenges. Material platforms discussed in this report are mainly polymer and silica. We categorize the hybridization methods using silica and polymer waveguides into two types, chip-to-chip and on-chip integration. General reviews of these hybridization technologies from the past works are reviewed. An example for each method is discussed in details. We also discuss current status of our silica PLC hybrid integration technology.

Hybrid integrated tunable optical transmitter subsystem on a chip

The need for tunable optical transmitters in optical networking is growing at a rapid rate. A tunable optical transmitter is the combination of a tunable laser, an isolator, and a modulator. Although today lasers and modulators could be integrated together on a single chip, an integrated component of this type would not be useful because the absence of an isolator between the two elements would cause optical reflections to reach the laser, leading to a high level of frequency chirp and relaxation oscillations. Therefore discrete external modulators are used, and lasers are coupled to them through discrete optical isolators. We report on recent developments in integrated active, thermo-optic, magneto-optic and electro-optic technologies that enable the production of a fully integrated tunable transmitter. This transmitter consists of a planar polymer waveguide circuit that is built on a silicon chip and in which films of a variety of materials are embedded. This subsystem on a chip includes a laser chip coupled to a thermo-optically tunable planar polymeric filter resulting in a tunable external cavity laser; an integrated magneto-optic isolator consisting of a planar polymer waveguide with inserted thin films of yttrium iron garnet for Faraday rotation, crystal ion sliced LiNbO3 for half-wave retardation, and polarizers; and an electro-optic modulator consisting of a crystal ion sliced LiNbO3 thin film patterned with a Mach-Zehnder interferometer and grafted into the polymer circuit, capable of operating with less than 5 Volts at modulation speeds up to 40 Ghz.

Ultra-Low-Power Compact PLC-Based 40-Channel ROADM Subsystem

We propose a 40-channel ROADM subsystem based on polymer and silica planar lightwave circuits. It exhibits ultra-low power consumption and compact size, while meeting the requirements for high optical performance, high reliability, and low cost.