All-fiber acousto-optic devices based on the null fused taper coupler have been successfully demonstrated as frequency shifters, variable splitters, switches and tunable filters. In this paper, the interaction upon which these devices are based has been extensively analyzed under a set of approximations that are valid in most cases. Simple analytical expressions for the important properties are derived, which provide a set of design rules for such devices.

The acousto-optic effect in single-mode fiber tapers and couplers

Si-photonic hybrid ring external cavity wavelength tunable lasers by passive alignment techniques with more than 100-mW fiber-coupled power and linewidth narrower than 15 kHz along the whole C-band are demonstrated. These attractive performances are achieved due to very low loss Si-wire waveguides, of which loss is lower than 0.5 dB/cm. Obtained results show excellent features of Si-photonics toward commercial products.

Silicon Photonic Hybrid Ring-Filter External Cavity Wavelength Tunable Lasers

Coherent detection offers high spectral efficiency and receiver sensitivity, but digital signal processing (DSP)-based coherent receivers may be prohibitively power hungry for data centers even when optimized for short-reach applications, where fiber propagation impairments are less severe. We propose and evaluate low-power DSP-free homodyne coherent receiver architectures for dual-polarization quadrature phase shift keying (DP-QPSK) for inter- and intradata center links. We propose a novel optical polarization demultiplexing technique, for DP-QPSK and higher-order modulation formats, with three cascaded phase shifters driven by marker tone detection circuitry. We consider carrier recovery based on either optical or electrical phase-locked loops (PLLs). We propose a novel multiplier-free phase detector based on XOR gates, which exhibits less than 0.5 dB power penalty relative to a conventional Costas loop phase detector. We also study the relative performance of homodyne DP-differential QPSK, for which carrier phase recovery is unnecessary. Our proposed DSP-free architectures exhibit ∼1 dB power penalty at small chromatic dispersion compared to their DSP-based counterparts. We estimate conservatively that the high-speed analog electronics of an electrical PLL-based coherent receiver consume nearly 4 W for 200 Gbit/s DP-QPSK, assuming a 90-nm complementary metal-oxide semiconductor process.

Design of Low-Power DSP-Free Coherent Receivers for Data Center Links

This paper reviews optical injection locking (OIL) of semiconductor lasers and its application in optical communications and signal processing. Despite complex OIL dynamics, we attempt to explain the operational principle and main features of the OIL in an intuitive way, aiming at a wide understanding of the OIL phenomenon and its associated techniques in the optic and photonic communities. We review and compare different control techniques that enable robust OIL in practical systems. The applications are reviewed with a focus on new developments in the past decade, under the categories of ‘High Speed Directly Modulated Lasers’ and ‘Optical Carrier Recovery’. Finally, we draw our vision for future research directions.

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Optical Injection Locking: From Principle to Applications

Elastic optical networks (EON) have been proposed to meet the network capacity and dynamicity challenges. Hardware and software resource optimization and re-configurability are key enablers for EONs. Recently, innovative multi-carrier transmission techniques have been extensively investigated to realize high capacity (Tb/s) flexible transceivers. In addition to standard telecommunication lasers, optical carrier generators based on optical frequency combs (OFC) have also been considered with expectations of reduced cost and inventory, improved spectral efficiency, and flexibility. A wide range of OFC generation techniques have been proposed in the literature over the past few years. It is imperative to summarize the state of the art, compare and assess these diverse techniques from a practical perspective. In this survey, we identify salient features of optical multicarrier generators, review and compare these techniques both from a physical and network layer perspective. OFC demultiplexing/filtering techniques have also been reviewed. In addition to transmission performance, the impact of such sources on the network performance and real-world deployment strategies with reference to cost, power consumption, and level of flexibility have also been discussed. Field trials, integrated solutions, and flexibility demonstrations are also reported. Finally, open issues and possible future directions that can lead to real network deployment are highlighted.

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A Survey of Optical Carrier Generation Techniques for Terabit Capacity Elastic Optical Networks

We have investigated the suitability of InP-based push-pull modulators to generate flat optical comb spectra. The residual amplitude modulation that was a consequence of driving the modulator well above its design voltage (up to 4V[pi]) is demonstrated to have no adverse effect for the comb generation. We also demonstrate generation of a comb with spacing equal to twice the repetition rate via control of the relative phase of the RF signals.

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Compact optical comb generator using InP tunable laser and push-pull modulator

We report the first demonstration of a 40 MHz four-port all-fiber frequency shifter operating at a wavelength of 1.55 /spl mu/m. The device has a high-conversion efficiency and low-drive power consumption, and is made from standard telecommunications fiber.

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40-MHz all-fiber acoustooptic frequency shifter

We report an InP coherent receiver chip with the highest reported responsivity (0.15A/W) together with excellent RF bandwidth (32GHz) and 4x4 MMI width fabrication control (< ±60nm 90% population) providing a highly manufacturable Rx for CFP2 modules

InP Coherent Receiver Chip with High Performance and Manufacturability for CFP2 Modules

We demonstrate a comb-based tunable transmitter with potential to be integrated on a single InP photonic chip. A Nyquist-shaped polarization-multiplexed 16QAM signal with 7.1 bit/s/Hz spectral efficiency is generated and transmitted over 300-km of SMF-28.

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InP-based optical comb-locked tunable transmitter

Tunable acousto-optic spectral filters based on null couplers have been improved by making the coupler more uniform A new double-pass arrangement further narrows the bandwidth, reduces the sidelobes to -20 dB and doubles the frequency shift

S.G. Farwell

Papers

Compact optical comb generator using InP tunable laser and push-pull modulator

40-MHz all-fiber acoustooptic frequency shifter

InP Coherent Receiver Chip with High Performance and Manufacturability for CFP2 Modules

InP-based optical comb-locked tunable transmitter

All-fibre acousto-optic tunable filter based on a null coupler