Interleavers

The chapter describes principles, analysis, design, properties, and implementations of optical frequency (or wavelength) interleavers. The emphasis is on finite impulse response devices based on cascaded Mach-Zehnder-type filter elements with carefully designed coupling ratios, the so-called resonant couplers. Another important class that is discussed is the infinite impulse response type, based on e.g. Fabry-Perot, Gires-Tournois, or ring resonators

Architectures for ku-band broadband airborne satellite communication antennas

This paper describes different architectures for a broadband antenna for satellite communication on aircraft. The antenna is a steerable (conformal) phased array antenna in Ku-band (receive-only). First the requirements for such a system are addressed. Subsequently a number of potential architectures are discussed in detail: a) an architecture with only optical true time delays, b) an architecture with optical phase shifters and optical true time delays and c) an architecture with optical true time delays and RF phase\ud shifters (or RF true time delays). The last two architectures use sub-arrays to reduce complexity of the antenna system. The advantages and disadvantages of the different architectures are evaluated and an optimal architecture is selected

Design and application of compact and highly tolerant polarization-independent waveguides

In this paper, the design, fabrication, and application of a highly tolerant polarization-independent optical-waveguide structure suited for operation in the third communication window is presented. The waveguide structure has been optimized toward minimized sensitivity to technological tolerances and low fabrication complexity. The tolerance analysis has been based on the typical processing tolerances of the widely applied silicon-oxynitride technology, being +/- $3 x 10^{-4}$ in refractive index, +/- 1% in thickness, and +/- 0.1 micron in channel width. The optimized waveguide design fulfills the criterion of a channel birefringence within $5 x 10^{-5}$, including processing tolerance. It also enables a fiber-to-chip coupling loss below 1 dB/facet and is suited for the realization of low-loss bends with a radius down to 600 micron. Based on this waveguide design, a passband-flattened optical wavelength filter with 50-GHz free spectral range has been realized and tested. The measured TE–TM shift of 0.03 nm confirms the polarization dependence of the optical waveguides being as low as $3 x 10^{-5}$

Novel ring resonator-based integrated photonic beamformer for broadband phased array receive antennas - part I: design and performance analysis

A novel optical beamformer concept is introduced that can be used for seamless control of the reception angle in broadband wireless receivers employing a large phased array antenna (PAA). The core of this beamformer is an optical beamforming network (OBFN), using ring resonator-based broadband delays, and coherent optical combining. The electro-optical conversion is performed by means of single-sideband suppressed carrier modulation, employing a common laser, Mach-Zehnder modulators, and a common optical sideband filter after the OBFN. The unmodulated laser signal is then re-injected in order to perform balanced coherent optical detection, for the opto-electrical conversion. This scheme minimizes the requirements on the complexity of the OBFN, and has potential for compact realization by means of full integration on chip. The impact of the optical beamformer concept on the performance of the full receiver system is analyzed, by modeling the combination of the PAA and the beamformer as an equivalent two-port RF system. The results are illustrated by a numerical example of a PAA receiver for satellite TV reception, showing that—when properly designed—the beamformer hardly affects the sensitivity of the receiver

Narrow linewidth hybrid InP-TriPleX photonic integrated tunable laser based on silicon nitride micro-ring resonators

Detailed characterization of a hybrid integrated tunable laser based on micro-ring resonators shows a tuning range of 50 nm with ~40 kHz linewidth. The device demonstrates performance comparable with commercial external cavity lasers in 16QAM coherent system

A novel polarization-independent wavelength-division-multiplexing filter based on cylindrical microresonators

A novel polarization-independent wavelength-division-multiplexing (WDM) filter, which exploits the strong polarization dependence of cylindrical microresonators by using them as wavelength-selective polarization splitters is presented. Detailed analysis of the polarization dependence of the filter shows that the filter is indeed virtually polarization-independent and has a wavelength response similar to the wavelength response of a microresonator coupled to two waveguides for a single polarization

A broadband high dynamic range analog photonic link using push-pull directly-modulated semiconductor lasers

We demonstrate an analog photonic link with a high multioctave spurious-free dynamic range (SFDR) of 119 dBHz2/3. The link consists of a pair of semiconductor DFB lasers modulated in a push-pull manner and a balanced photodetector. With precise amplitude and phase matchings, a signal enhancement of 4.5 dB and a second-order intermodulation distortion suppression of 40 dB relative to the case of a single arm optical link with one laser can be achieved. To our knowledge, the measured SFDR is one of the highest broadband value ever achieved with directly modulated lasers. Index Terms—Intermodulation distortion, laser noise, optical modulation, semiconductor laser

High-Selectivity On-Chip Optical Bandpass Filter With Sub-100-MHz Flat-Top and Under-2 Shape Factor

We demonstrate a fully tunable microwave photonic bandpass filter fabricated with Si3N4/SiO2 waveguides on a chip. The filter is based on coupled resonator optical waveguide architecture comprising a chain of eight coupled ring resonators, each with an optical roundtrip length of 21 cm (free spectral range of 1.4 GHz), with an adjustable resonance frequency, and with adjustable power coupling. The passband shows a 3-dB bandwidth of 72 MHz with at least 51-dB out-of-band rejection and features simultaneously a flat-top, a shape factor of 1.9, and a group delay variation smaller than 2 ns