Tarek Al Abbas

A SPAD-Based Visible Light Communications Receiver Employing Higher Order Modulation

This paper studies complex modulation schemes, including orthogonal frequency-division multiplexing (OFDM), received by a single photon avalanche diode (SPAD) array integrated circuit (IC). A SPAD operates in the Geiger mode, and is able to detect single photons. This feature enables order of magnitude receiver sensitivity in intensity modulation (IM) / direct detection (DD) Visible Light Communication (VLC) systems. The tradeoff between received power and bit error ratio (BER) using both pulse-amplitude modulation (PAM) and OFDM is shown. A first order model of the noise in a digital SPAD receiver is derived. The noise in the experimental receiver chip approaches the predicted noise in our model, and we achieve receiver sensitivity of

4-PAM visible light communications with a XOR-tree digital silicon photomultiplier

-

High Dynamic Range Imaging at the Quantum Limit with Single Photon Avalanche Diode-Based Image Sensors

64 dBm with a 100 kbit/s signal at a BER of 10^-5. It is concluded that future improvements in SPAD VLC receiver architecture will allow sensitivity to approach the quantum limit.

Advances in CMOS SPAD sensors for LIDAR applications

We show reception of a higher order modulation scheme using a novel high-fill-factor XOR-tree based digital silicon photomultiplier array. We also demonstrate and model even-order XOR cancellation and nonlinear saturation resulting from this design.

Hypervelocity time-of-flight characterisation of a 14GS/s histogramming CMOS SPAD sensor

This paper examines methods to best exploit the High Dynamic Range (HDR) of the single photon avalanche diode (SPAD) in a high fill-factor HDR photon counting pixel that is scalable to megapixel arrays. The proposed method combines multi-exposure HDR with temporal oversampling in-pixel. We present a silicon demonstration IC with 96 × 40 array of 8.25 µm pitch 66% fill-factor SPAD-based pixels achieving >100 dB dynamic range with 3 back-to-back exposures (short, mid, long). Each pixel sums 15 bit-planes or binary field images internally to constitute one frame providing 3.75× data compression, hence the 1k frames per second (FPS) output off-chip represents 45,000 individual field images per second on chip. Two future projections of this work are described: scaling SPAD-based image sensors to HDR 1 MPixel formats and shrinking the pixel pitch to 1–3 µm.

Object Tracking and Reconstruction with a Quanta Image Sensor

Single-Photon Avalanche Diode (SPAD) sensors are one of the detectors of choice in LIDAR applications, due to their high sensitivity and time resolution. Traditionally, single-point SPAD detectors have been used, necessitating optical scanning, and hence leading to slower acquisition times. However, recent advances in SPAD technology have yielded high pixel count imagers. In these sensors, high sensitivity is ensured by maximising the photo-sensitive area of the device, whilst time-resolved capability is offered by the time stamping of photon detections and/or a programmable timegate synced to the laser source. The resulting sensors show an exciting promise for LIDAR, especially in challenging, low-light, high-speed applications.

Invited Paper - Single-Photon-Capable Detector Arrays in CMOS: Exploring a New Tool for Display Metrology

We present Time-of-Flight (TOF) distance, velocity and acceleration characterisation of a multi-event Time-to-Digital- Converter (TDC) optical sensor featuring a 32x32 Single Photon Avalanche Diode (SPAD) array, a 14 GS/s TDC and on-chip histogram generation. Events are continuously recorded on-chip in 264 70 ps-wide histogram bins. High TDC throughput enables the device to be operated in Doppler mode with pulse-trains moving at hypervelocity speeds relative to the operational sensor frequency. Electrical frequency-detuned signals of 50 kHz are resolved by the TDC module. Optical frequency-detuned signals of 1 kHz are resolved, corresponding to a TOF velocity resolution of 15.8 km/s. Linear, sine-wave, and chirp frequency modulation techniques are used to demonstrate these characteristics.