  Several photonic microring resonators (MRRs) based analog accelerators have
been proposed to accelerate the inference of integer-quantized CNNs with
remarkably higher throughput and energy efficiency compared to their electronic
counterparts. However, the existing analog photonic accelerators suffer from
three shortcomings: (i) severe hampering of wavelength parallelism due to
various crosstalk effects, (ii) inflexibility of supporting various dataflows
other than the weight-stationary dataflow, and (iii) failure in fully
leveraging the ability of photodetectors to perform in-situ accumulations.
These shortcomings collectively hamper the performance and energy efficiency of
prior accelerators. To tackle these shortcomings, we present a novel Hybrid
timE Amplitude aNalog optical Accelerator, called HEANA. HEANA employs hybrid
time-amplitude analog optical multipliers (TAOMs) that increase the flexibility
of HEANA to support multiple dataflows. A spectrally hitless arrangement of
TAOMs significantly reduces the crosstalk effects, thereby increasing the
wavelength parallelism in HEANA. Moreover, HEANA employs our invented balanced
photo-charge accumulators (BPCAs) that enable buffer-less, in-situ, temporal
accumulations to eliminate the need to use reduction networks in HEANA,
relieving it from related latency and energy overheads. Our evaluation for the
inference of four modern CNNs indicates that HEANA provides improvements of
atleast 66x and 84x in frames-per-second (FPS) and FPS/W (energy-efficiency),
respectively, for equal-area comparisons, on gmean over two MRR-based analog
CNN accelerators from prior work.
