Interferometric switches for transparent networks : development and integration

Magneto-optic devices are a potential enabler of better scaling, transparent networks that are bit-rate, protocol and format insensitive. Transparency is critical given the paradigm shift from connection-oriented communications to IP-centric packet switched data traffic driven by the influx of high bandwidth applications. This is made more urgent by the large and growing optical-electronic bandwidth mismatch as well as the rapid approach of device dimensions to the quantum limit. Fiber-based switches utilizing bismuth-substituted iron garnets as Faraday rotators in Mach-Zehnder and Sagnac interferometer configurations are proposed, analyzed and characterized. The issues and limitations of these switches are investigated and efforts are undertaken to model and optimize the field generating coil impedance parameters. While alleviating the concerns associated with free-space switches and being compatible with contemporary optical networks, the performance of the fiber-based interferometric switches is still below theoretical limits and could be improved. Moreover, the discrete components of a fiber-based implementation engender scalability concerns. In keeping with the spirit of Richard Feynman\u27s lectures, the maturity of planar lithographic techniques that are widely used in microelectronics is leveraged to realize integrated versions of the fiber-based interferometric switches. The design, analysis, fabrication and characterization of these integrated switches are detailed herein, including the selection of a suitable material system, design of the waveguide geometry, creation and calibration of a fabrication process based on direct-write scanning electron-beam lithography as well as determination of the switches\u27 fabrication tolerance. While the larger waveguide cross-section of the microphotonic switches enables efficient coupling to fiber and greatly reduces geometrical birefringence, the weak confinement results in longer device lengths. Moreover, the small but finite birefringence induces some polarization dependence in switch performance. Consequently, compact and nominally non-birefringent nanophotonic versions of the interferometric switches are proposed and analyzed in the interest of further improving switch performance and scalability

Optimization of Magnetooptic Device by Low Switching Field Domains

This paper expounds on the optimization of magnetooptic devices using preferential domains that switch at low field strengths. In particular, an all-optical switch for transparent networks based on theMach-Zehnder interferometer configuration is examined in detail. The switch utilizes bismuth-substituted iron garnets with a specific composition of (Bi1.1Tb1.9)(Fe4.25Ga0.75)O12 as Faraday rotators. It is proposed that switch figures of merit can be improved by preferentially choosing domains which align with applied fields at field strengths much lower than required by the bulk material. Measurement of magnetic domain orientation in the material and Faraday rotation within domains is reported. The domain behavior in low magnetic fields is also investigated to achieve a switch with lower switching times and higher extinction ratios

Improved formulation for Faraday rotation characterization

The analysis of complex structures consisting of fibers, films, birefringent, and magnetic materials is greatly aided by the availability of an analysis structure. Jones calculus is typically utilized in the course of such analyses. However, standard Jones calculus does not account for the effect of reflections. An improved formulation for the characterization of Faraday rotation that alleviates this shortcoming is reported here and is integral for the proper analysis of devices employing magneto-optic effects

Interferometric switches for transparent networks : development and integration

Magneto-optic devices are a potential enabler of better scaling, transparent networks that are bit-rate, protocol and format insensitive. Transparency is critical given the paradigm shift from connection-oriented communications to IP-centric packet switched data traffic driven by the influx of high bandwidth applications. This is made more urgent by the large and growing optical-electronic bandwidth mismatch as well as the rapid approach of device dimensions to the quantum limit. Fiber-based switches utilizing bismuth-substituted iron garnets as Faraday rotators in Mach-Zehnder and Sagnac interferometer configurations are proposed, analyzed and characterized. The issues and limitations of these switches are investigated and efforts are undertaken to model and optimize the field generating coil impedance parameters. While alleviating the concerns associated with free-space switches and being compatible with contemporary optical networks, the performance of the fiber-based interferometric switches is still below theoretical limits and could be improved. Moreover, the discrete components of a fiber-based implementation engender scalability concerns. In keeping with the spirit of Richard Feynman's lectures, the maturity of planar lithographic techniques that are widely used in microelectronics is leveraged to realize integrated versions of the fiber-based interferometric switches. The design, analysis, fabrication and characterization of these integrated switches are detailed herein, including the selection of a suitable material system, design of the waveguide geometry, creation and calibration of a fabrication process based on direct-write scanning electron-beam lithography as well as determination of the switches' fabrication tolerance. While the larger waveguide cross-section of the microphotonic switches enables efficient coupling to fiber and greatly reduces geometrical birefringence, the weak confinement results in longer device lengths. Moreover, the small but finite birefringence induces some polarization dependence in switch performance. Consequently, compact and nominally non-birefringent nanophotonic versions of the interferometric switches are proposed and analyzed in the interest of further improving switch performance and scalability.</p

Magnetically Controlled Switches for Optoelectronics Networking: The Problem, Available Technology, New Implementations

This paper introduces some physical layer requirements of electro-optical as well as all optical networking. Due to the huge volume of data that is transmitted on these networks, there is a need for high-speed switching with effective switching in the nanosecond regime or better. While such switches exist for electronic media, they have been challenging for optical applications. Taking the recent developments in magneto-optical switches into consideration, there is a pressing need for fast switching of highly inductive loads. The state-of-the-art as well as the trends and needs for high speed switching in optical networks are presented. Some of the newest developments in the small-scale high-speed switching for electro-optical and all optical light path applications will also be presented. Experimental results of the newly developed switches at our program are presented and discussed. Based on the results, system requirements are identified and some shortcomings of the initial system are addressed. Possible improvements to the overall light-trail system are proposed and discussed

Optimization of Magnetooptic Device by Low Switching Field Domains

This paper expounds on the optimization of magnetooptic devices using preferential domains that switch at low field strengths. In particular, an all-optical switch for transparent networks based on theMach-Zehnder interferometer configuration is examined in detail. The switch utilizes bismuth-substituted iron garnets with a specific composition of (Bi1.1Tb1.9)(Fe4.25Ga0.75)O12 as Faraday rotators. It is proposed that switch figures of merit can be improved by preferentially choosing domains which align with applied fields at field strengths much lower than required by the bulk material. Measurement of magnetic domain orientation in the material and Faraday rotation within domains is reported. The domain behavior in low magnetic fields is also investigated to achieve a switch with lower switching times and higher extinction ratios.This article is from ISRN Optics 2012: 865794, doi: 10.5402/2012/865794. Posted with permission.</p