This tutorial describes the transmission, group delay time and quadratic dispersion properties of the four basic building blocs of optical filters built using ring resonators. These building blocs are single-ring resonators in either two-port (all-pass) or four-port (add/drop filter) configuration. The effect of waveguide and coupler loss is included throughout. Explicit expressions to compute the complex amplitude of the circulating wave in the ring, the Q factor, the finesse and the insertion loss are also given. Attention is drawn to the similarities between the ring resonator the Fabry-Pe/spl acute/rot resonator and the Gires-Tournois interferometer. Material properties and fabrication technology are not reviewed.

Transmission, group delay, and dispersion in single-ring optical resonators and add/drop filters-a tutorial overview

Two practical implementations of endless polarization control are described. The first approach uses polarization maintaining fiber transducer, while the second uses an integrated optic lithium niobate device. In order to characterize the lithium niobate device in detail, a technique for analyzing the birefringence as a function of the applied voltages was developed, and the measured performance of the devices is presented. Fractional-wave controllers for both static and endless control applications are considered, and design rules for maximum wavelength-window and minimum loss fiber-loop polarization adjusters are given. Endless control using various configurations of the three types of transducers is discussed, and it is shown how apparently different schemes are closely related. >

Polarization control for coherent communications

Ultra-High-Q Photonic Double-Heterostructure Nanocavity

An optical apparatus comprises an optical device fabricated on a substrate, an external-transfer optical waveguide fabricated on the substrate and/or on the optical device, and a transmission optical waveguide. The optical device and/or the external-transfer waveguide are adapted for and positioned for transfer of optical power therebetween (end-transfer or transverse-transfer). The external-transfer waveguide and/or the transmission waveguide are adapted for transverse-transfer of optical power therebetween (mode-interference-coupled or adiabatic). The transmission waveguide is initially provided as a component mechanically separate from the substrate, device, and external-transfer waveguide. Assembly of the transmission waveguide with the substrate, device, and/or external-transfer waveguide results in relative positioning of the external-transfer waveguide and the transmission waveguide for enabling transverse-transfer of optical power therebetween. Optical power transfer between the device and the transmission waveguide through the external-transfer waveguide is thereby enabled. The transmission waveguide may preferably comprise a planar waveguide on a waveguide substrate.

Optical junction apparatus and methods employing optical power transverse-transfer

This paper reviews ultrahigh-speed data transmission in optical fibers based on optical time division multiplexing (OTDM) transmission technology. Optical signal processing in the transmitter and receiver as well as the requirements on ultrahigh-speed data transmission over a fiber link are discussed. Finally, results of several OTDM-transmission experiments, including 160-Gb/s transmission over 4320 km, 1.28-Tb/s transmission over 240 km, and 2.56-Tb/s transmission over 160-km fiber link, are described

Ultrahigh-Speed OTDM-Transmission Technology

Experiments on the optical generation and transmission of millimeter-wave radio signals are reported. The millimeter-wave signals are generated by heterodyning the optical spectral lines of a mode-locked laser (MLL) or of two or more semiconductor lasers at an optic/millimeter-wave converter (OMC). 70-, 140-, and 155-Mb/s data transmission experiments have been carried out successfully in optical single-channel and multichannel systems at radio frequencies of 12 GHz and 58-70 GHz. Bit-error-rate measurements yielded error-free transmission and no error floor was observed. A monolithically integrated tunable optical-signal source was developed and used for generating the millimeter-wave signals. This technology promises a high cost-saving potential for applications in radio-over-fiber systems.

Optical microwave generation and transmission experiments in the 12- and 60-GHz region for wireless communications

A racetrack shaped double ring resonator (DRR) filter is demonstrated with radii of 200 µm. The double ring resonator contains two -3 dB multimode interference (MMI) couplers for I/O coupling and a -13 dB codirectional coupler in between the rings. A free spectral range of 50 GHz has been realized. A simulation model has been developed to describe the DRR. As fabrication tolerances do not allow the realization of two identical rings with required nm-circumference accuracy in the resonator, a frequency alignment of the resonator is indispensable. The resonance frequency tuning is performed thermally using platinum resistors which have been placed on top of the waveguides in both rings. An on-off ratio increase has been achieved of more than 3 dB, resulting in a total on-off ratio larger than 18 dB. The frequency alignment is inevitable in the case of multiple coupled micro ring resonators.

https://iopscience.iop.org/article/10.1143/JJAP.41.1186/pdf

Resonance Frequency Tuning of a Double Ring Resonator in GaInAsP/InP: Experiment and Simulation

Beam spread transformers are required for chip-fibre couplings and must be polarisation-independent, show low losses and be economically produced. In a beam spread transformer (1) with an integrated structure having several buffer layers (5) mutually separated by conductive layers (6), an uncladded rib waveguide (7, 8) with a tapering area (9) is arranged on the top buffer layer (5). A section (11) over which the rib (8) extends is located between the interface (2) with the fibre and the tapering area (9). The waveguide layer (7) is completely removed from this section and the exposed buffer layer (5) is reduced to a width w2 which exceeds the width w1 of the continuous rib (8) in a symmetrical manner. The thus obtained additional rib (12) makes it possible for the coupling to be polarisation-independent and to be optimised with the increased heights (d1, d2, d3) thanks to the buffer layers (5).

Integrated optical beam spread transformer

The state of the art in the fabrication of heterodyne receiver photonic integrated circuits (PICs) is described and in particular the results and experiences of the first fabrication of polarization-insensitive heterodyne receiver PICs are emphasized. The fabrication is based on a versatile integration concept with the potential also to fabricate other PIC architectures with different functionalities by only a single fabrication process.

Helmut Heidrich

Papers

Optical microwave generation and transmission experiments in the 12- and 60-GHz region for wireless communications

Resonance Frequency Tuning of a Double Ring Resonator in GaInAsP/InP: Experiment and Simulation

Integrated optical beam spread transformer

Heterodyne receiver PICs as the first monolithically integrated tunable receivers for OFDM system applications

Optoelectronic/Photonic Integrated Circuits on InP between Technological Feasibility and Commercial Success