Abhijeet Ardey

A 25 Gb/s Burst-Mode Receiver for Low Latency Photonic Switch Networks

A DC-coupled burst-mode receiver performs optical power calibration in 12.5ns, achieves phase lock in 18.5ns and tracks input data using a CDR. The sensitivity of the 4.4pJ/bit receiver is -10.9dBm (BER <; 10-12) at 25Gb/s.

30-Gb/s Optical Link Combining Heterogeneously Integrated III–V/Si Photonics With 32-nm CMOS Circuits

We present a silicon photonics optical link utilizing heterogeneously integrated photonic devices driven by low-power advanced 32-nm CMOS integrated circuits. The photonic components include a quantum-confined Stark effect electroabsorption modulator and an edge-coupled waveguide photodetector, both made of III-V material wafer bonded on silicon-on-insulator wafers. The photonic devices are wire bonded to the CMOS chips and mounted on a custom PCB card for testing. We demonstrate an error-free operation at data rates up to 30 Gb/s and transmission over 10 km at 25 Gb/s with no measured sensitivity penalty and a timing margin penalty of 0.2 UI.

A Linearized Intensity Modulator for Photonic Analog-to-Digital Conversion Using an Injection-Locked Mode-Locked Laser

A linearized intensity modulator for pulsed light based on an injection-locked mode-locked laser (MLL) is presented here. This has been realized by introducing a monolithic Fabry-Pérot MLL into one of the arms of a conventional Mach-Zehnder interferometer (MZI) and injection-locking it to a MLL which is the input to the interferometer. By modulating the current on the gain section or the voltage of the saturable absorber (SA) section of the injection-locked laser, one can introduce an arcsine phase response on each of the injected longitudinal modes. By combining the modulated optical comb with its unmodulated counterpart one can produce a linearized intensity modulator. The linearity of this modulator is inherent in its design and no pre- or postdistortion linearization scheme is utilized. The results of the two-tone intermodulation experiment are presented here for this modulator and a spur-free dynamic range (SFDR) of ~70 dB·Hz2/3 is achieved by modulating the voltage of the SA. The reported SFDR is limited by the noise of the MLLs. The dynamic range could be further improved by decoupling the phase modulation and amplitude modulation. The proposed and demonstrated configuration as an analog optical link with improved linearity has the potential to increase the performance and resolution of photonic analog-to-digital converters (ADCs).

Optical and RF stability transfer in a monolithic coupled-cavity colliding pulse mode-locked quantum dot laser

We report a novel quantum dot based laser design where a stable high-Q master laser is used to injection lock a passively mode-locked monolithic colliding pulse slave laser. Coupling between the crossed orthogonal laser cavities is achieved through a common monolithically integrated saturable absorber, which results in the locking and hence reduction of the timing jitter as well as the long-term frequency drift of the slave laser. A stable 30 GHz optical pulse train is generated with more than 10 dB reduction in the RF noise level at 20 MHz offset and close to 3 times reduction in the 10 dB average optical linewidth of the slave laser.

22.1 A 25Gb/s burst-mode receiver for rapidly reconfigurable optical networks

Rapidly reconfigurable optical networks that keep the data in the optical domain potentially offer significant advantages in latency, bandwidth and power dissipation. Existing optical switch technologies (e.g., MEMS-based) are limited to millisecond-scale reconfiguration times, severely reducing their application space. The emerging field of silicon photonics enables optical switches operating on a nanosecond scale [1]. However, full utilization of the speed of these switches requires nanosecond-scale burst-mode transceivers, similar to those used in passive optical networks [2]. In this work, we reporta burst-mode receiver for optical links in a dynamically reconfigurable network. Through the introduction of interlocking search algorithms, a robust 25Gb/s burst-mode operation is achieved with 31ns lock time, -10.9dBm sensitivity, and 4.4pJ/b efficiency.

Towards linear interferometric intensity modulator for photonic ADCs using an injection locked AlInGaAs quantum well Fabry-Pérot laser

A monolithic AlInGaAs quantum well Fabry-Pérot laser injection locked to a passively mode-locked monolithic laser is presented here. The FP laser cavity can be used as a true linear interferometric intensity modulator for pulsed light.

Dispersion measurements of a 1.3 μm quantum dot semiconductor optical amplifier over 120 nm of spectral bandwidth

Group delay and higher order dispersion measurements are conducted on a 1.3 μm quantum dot semiconductor optical amplifier at various injection currents. White-light spectral interferometry is performed, along with a wavelet transform to recover the group delay. The group delay, group velocity dispersion, and higher order dispersion terms are quantified. The measurement spans both ground state and first excited state transitions, ranging from 1200 to 1320 nm. The group velocity dispersion, β2, is found to be −6.3×103 fs2 (7.6 fs/nm) at an injection current of 500 mA.

All Optical Stabilization of a Monolithic Quantum Dot Based CPM Laser Via Four-Wave Mixing

We investigate and confirm a four-wave mixing (FWM) process as the primary mechanism responsible for locking and stabilization of a previously reported novel quantum dot based monolithically coupled colliding pulse mode-locked (CPM) laser. In the previous letter, a high-Q passively mode-locked ring laser is used to injection lock an orthogonally coupled passively mode-locked CPM slave laser via FWM in the common saturable absorber. In this letter, we setup an experiment to verify the FWM process, whereby the external ring laser is operated unidirectionally while simultaneously analyzing the amplified spontaneous emission from the other facet of the ring laser. The emission is found to contain CPM light only in the presence of injection locking proving the FWM process. Other linear scattering effects are also investigated and shown to be negligible in the orthogonal waveguide configuration.

High-Q Transfer in Nonlinearly Coupled Mode-Locked Semiconductor Lasers

A novel four-wave mixing-based injection locking method was demonstrated earlier, whereby the optical and RF stability of a mode-locked high-Q ring laser is successfully transferred to an orthogonally coupled colliding pulse mode-locked (CPM) laser. Four-wave mixing in the common monolithically integrated saturable absorber is used to couple the crossed laser cavities, which is confirmed by the reduction in RF noise level and by the optical linewidth reduction of the lasing modes of the slave CPM laser. The four-wave mixing process was then further investigated and experimentally shown to be the primary mechanism responsible for the locking and stabilization of the slave laser. This paper discusses the above four-wave mixing technique in detail and presents an improved design by employing optical subharmonic hybrid mode-locking and by decreasing the losses inside the master ring cavity. The resulting higher stability of the master laser translates into further improvement in the RF and optical linewidths of the injection locked slave CPM laser. These results demonstrate the effectiveness of the novel method for all on-chip stability transfer in the forthcoming all monolithic optical pulse source systems.

A 25 Gb/s burst-mode receiver for low latency photonic switch networks

We report a dc-coupled burst-mode (BM) receiver for optical links in a dynamically reconfigurable network. Through the introduction of interlocking search algorithms, a robust 25 Gb/s BM operation is achieved with 31 ns lock time. At the beginning of the burst, the receiver first performs input dc current offset calibration in 12.5 ns, then achieves phase lock in 18.5 ns, and after that tracks data using a phase interpolator (PI) based bang-bang clock and data recovery (CDR). The sensitivity of the receiver is -10.9 dBm (average power, BER <; 10-12) at 25 Gb/s, tested with a single mode 1550 nm reference optical transmitter. There is no significant sensitivity penalty in the presence of ±100 ppm frequency offset between the transmitter and the receiver. Measured power efficiency of the receiver at 25 Gb/s is 4.4 pJ/bit. The core of the 32 nm SOI CMOS circuit occupies 200 μm × 300 μm.