1.6 Tb/s optical engine is enabled through vertical integration of a 2-channel monolithic InP PIC with SiGe electronics and a real-time DSP ASIC operating at 100 Gbaud for 800 Gb/s transmission.

We present a 1.6Tbps coherent transceiver delivering 800Gbps/wave transmission using integrated Tx/Rx functions with 50GHz bandwidth and 50kHz linewidth tunable lasers on a single 2-channel InP PIC, paired with a SiGe Driver and TIA ASIC.

This paper reports the effectiveness of a variety of single- and dual-loop optical feedback arrangements on stability of self-mode-locked two-section quantum dash lasers emitting at approximate to 1.55 mu m and operating at 21 GHz repetition rate. We describe reduction of RF linewidth and timing jitter using five distinct schemes, including single and dual loops with symmetric and asymmetric lengths, and with balanced and unbalanced feedback ratios. All feedback schemes described are effective in stabilizing the pulse trains from SML QDash lasers, but some require precisely tuned resonance between loop delay and laser cavity. We show balanced asymmetric dual-loop optical feedback is the most robust, cost-effective and low-noise method to stabilize and control pulses from mode-locked lasers and optoelectronic oscillators.

Feedback stabilization of high repetition-rate optical pulses from semiconductor mode-locked lasers (MLLs) with low noise performance is of special interest for optical clock recovery, lidar, optical frequency combs, high-speed data sampling, and optical time division multiplexing [1, 2], among other applications. It is highly desirable for feedback-based stabilization to achieve reduced sensitivity to drift of the optical phase/delay in the feedback loop, caused by aging, manufacturing tolerances or environmental changes. We have demonstrated reduced sensitivity of semiconductor MLLs to drift in optical delay using various dual-loop optical feedback schemes [3-5].

A novel asymmetric dual-loop configuration suppresses parasitic noise-resonances when single- and dual-loop optical feedback is used to stabilize mode-locked quantum-dash lasers at 1550 nm. Conditions for optimum suppression are determined and compared with published theory.

In this paper, we report stabilization of self-mode-locked two-section quantum-dash lasers on the widest range of delay using simultaneous optical injection and optical feedback. With continuous-wave optical injection, various wavelengths spanning a range from 1568 to 1578 nm were investigated and optimum wavelengths (1571.210 to 1572.710) yielding the narrowest RF linewidth and reduced timing jitter of slave laser were identified. In addition, the dependence of RF linewidth and pulse repetition rate on injected wavelength was further explored. Our results indicate that simultaneous optical feedback and optical injection significantly improves the RF linewidth across the widest delay range compared to optical feedback alone. Under fully resonant feedback and optimum injection parameters, a minimum RF linewidth of 1 kHz (instrument limited) was achieved with simultaneous optical injection plus optical feedback, which was >2x lower than optical feedback alone and more than 100x lower than free-running. This stabilization technique is implemented in an all-optical arrangement without optical/electrical conversion, which is ideal for high-repetition-rate devices and photonic integration. (C) 2018 Optical Society of America

We report experimental studies of the influence of symmetric dual-loop optical feedback on the RF linewidth and timing jitter of self-mode-locked two-section quantum dash lasers emitting at 1550 nm. Various feedback schemes were investigated and optimum levels determined for narrowest RF linewidth and low timing jitter, for single-loop and symmetric dual-loop feedback. Two symmetric dual-loop configurations, with balanced and unbalanced feedback ratios, were studied. We demonstrate that unbalanced symmetric dual loop feedback, with the inner cavity resonant and fine delay tuning of the outer loop, gives the narrowest RF linewidth and reduced timing jitter over a wide range of delay, unlike single and balanced symmetric dual-loop configurations. This configuration with feedback lengths of 80 and 140 m narrows the RF linewidth by ∼ 4-67x and ∼ 10-100x, respectively, across the widest delay range, compared to free-running. For symmetric dual-loop feedback, the influence of different power split ratios through the feedback loops was determined. Our results show that symmetric dual-loop feedback is markedly more effective than single-loop feedback in reducing RF linewidth and timing jitter, and is much less sensitive to delay phase, making this technique ideal for applications where robustness and alignment tolerance are essential.

We demonstrate a novel dual-loop scheme to suppress external cavity side-bands and modal overlaps induced in spectrum of self-mode-locked laser resulting from conventional single loop feedback and dual loop feedback configurations.

We have experimentally investigated the RF linewidth and timing jitter in self-mode-locked two-section quantum dash lasers emitting at ~1.55 μm and operating at ~21 GHz repetition rate, subjected to single and dual loop optical feedback into the gain section, over a wide range of feedback delay. Various feedback conditions are investigated and optimum levels determined for narrowest linewidth and reduced timing jitter for both single and dual-loop configurations. We demonstrate that dual-loop feedback with the shorter feedback cavity tuned to be fully resonant, followed by fine tuning of the phase of the longer feedback cavity, gives stable narrow RF spectra across the widest delay range, 10 - 50× better than single-loop feedback. In addition, for dual-loop configurations, under fully resonant conditions, phase noise is reduced to 295 fs [10 kHz - 100 MHz], the RF linewidth narrows to <; 1 kHz, with more than 30 dB fundamental side-mode suppression. We show that dual-loop optical feedback with separate fine tuning of both external cavities is far superior to single-loop feedback, with increased system tolerance against phase delay mismatch, making it a robust and cost-effective technique for developing practical, reliable and low-noise mode-locked lasers, optoelectronic oscillators and pulsed photonic circuits.

We propose a novel self-homodyne optical-electrical-optical clock recovery technique for binary phase-shift keying (BPSK) signals using commercial optical and electrical components. We present the principle of operation as well as a proof-of-concept experiment for a 10.7 Gb/s BPSK signal clock recovery transmitted over a dispersion-compensated link of 20 km of single-mode fiber. Suppression of pattern-related frequency noise at the output of the recovered clock is shown. The timing jitter of the recovered clock at 10.7 GHz was measured to be ∼450  fs (integration range: 100 Hz-10 MHz).

We numerically demonstrate the effect of optical injection induced modulation of the phase-amplitude coupling (factor α) on power spectra and optical characteristics in mutually coupled lasers system with finite delay. We observed the signature of tunable phase locked laser emission (coherent In-phase and Anti-phase) by directly controlling the nonlinearity via manipulating phase-amplitude coupling. In addition, we predict the occurrence of frequency discretization and multistability near the phase transitions regimes, which could be useful in guiding the design of both experimental setup and compact photonic integrated practical devices for the generation of higher power laser system with the aid of optical phase control.

We experimentally investigate the RF linewidth and timing jitter over a wide range of delay tuning in a self-mode-locked two-section quantum dash lasers emitting at ~ 1.55μm and operating at ~ 21 GHz repetition rate subject to single and dual optical feedback into gain section. Various feedback conditions are investigated and optimum levels determined for narrowest linewidth and reduced timing jitter for both single and dual loop configurations. We demonstrate that dual loop feedback, with the shorter feedback cavity tuned to be fully resonant, followed by fine tuning of the phase of the longer feedback cavity, gives stable narrow RF spectra across the widest delay range, unlike single loop feedback. In addition, for dual loop configurations, under fully resonant conditions, integrated timing jitter is reduced from 3.9 ps to 295 fs [10 kHz-100 MHz], the RF linewidth narrows from 100 kHz to < 1 kHz, with more than 30 dB fundamental side-mode suppression. We show that dual loop optical feedback with separate fine tuning of both external cavities is far superior to single loop feedback, with increased system tolerance against phase delay mismatch, making it a robust and cost-effective technique for developing practical, reliable and low-noise mode-locked lasers, optoelectronic oscillators and pulsed photonic circuits.

We demonstrate a symmetric dual loop feedback scheme, insensitive to delay phase tuning, for a self-mode-locked quantum dash laser emitting at ~ 1.55 μm and operating at ~ 21 GHz repetition rate. These lasers are subjected to single and dual loop optical feedback into the gain section. Various feedback conditions are studied and optimum levels determined for narrowest linewidth and reduced timing jitter for both single and symmetric dual loop configurations. We demonstrate that symmetric dual loop with the inner cavity fully resonant and the outer one slightly offset, produces narrowed RF spectra across the widest delay range. In general, symmetric dual loop feedback is far more effective than single loop feedback in reducing RF linewidth and timing jitter, across a much wider range of delay phase. Resonant conditions for dual loop feedback are nearly independent of delay, making it ideal for practical applications where robustness and tolerance to misalignment are essential.

We report effects of varying feedback ratios and phases in dual-loop external optical feedback on phase-noise characteristics of passively mode-locked two-section quantum-dash lasers. Optimal feedback yields ~100× reductions in RF-linewidth.

We report a unidirectional frequency dissemination scheme for high-fidelity optical carriers deployable over telecommunication networks. For the first time, a 10 Gb/s Binary Phase Shift Keying (BPSK) signal from an ultra-narrow linewidth laser was transmitted through a field-installed optical fibre with round-trip length of 124 km between Cork City and town of Clonakilty, without inline optical amplification. At the receiver, using coherent communication techniques and optical injection-locking the carrier was recovered with noise suppression. The beat signal between the original carrier at the transmitter and recovered carrier at the receiver shows a linewidth of 2.8 kHz. Long term stability measurements revealed fractional instabilities (True Allan deviation) of 3.3 × 10(-14) for 1 s averaging time, prior to phase noise cancellation.

We report for the first time an ultra-stable optical-carrier dissemination technique for transmission over a 20 km unidirectional fibre link. The optical-linewidth of the recovered carrier matches closely that of the original carrier.

We introduce a novel scheme for the simultaneous reduction of time-bandwidth product (TBP) and RF linewidth of quantum-dash two-section mode-locked lasers using optical injection-locking and filtered optical feedback. The optical injection-locked laser, double-locked with optical feedback showed 2x TBP reduction and RF linewidth reduction by two orders of magnitude. This stabilization technique is implemented in an all-optical arrangement without optical/electrical conversion which is ideal for high-repetition-rate devices and photonic integration.

We demonstrate narrow pulses with low RF linewidth from two-section InP quantum-dash mode-locked lasers. Simultaneous CW injection-locking and selective optical feedback lead to ≃50 times RF linewidth and 1.5 times time-bandwidth product reduction.