We propose to design and deliver a turn-key photon counting detector module for near-infrared wavelengths, based on large-area InGaAs/InP avalanche photodiodes (APDs) that have been optimized for photon counting. The detector module will incorporate all of the essential photon-counting detector system elements: thermoelectric cooling, high-speed bias gating and avalanche quenching circuits, power supply, control and signal interfaces, optical fiber input, and a large-area APD. Previous near-infrared photon-counting systems have been severely limited by the use of commercially-available telecommunications-grade APDs, designed for linear operation at room temperature and low internal gain. These APDs are far from optimum for single photon counting at reduced temperature and very high internal gain. Work by our company has demonstrated that both quantum efficiency and pulse jitter can be greatly improved using APDs developed specifically for photon counting. During Phase I we will develop and deliver a prototype photon counting detector module optimized for low jitter and high single-photon quantum efficiency at wavelengths between 1.0 and 1.6 microns. During Phase II we will deliver a more advanced detector module having interchangeable APDs individually optimized for photon counting in the 1.0, 1.5, and 1.9 micron wavelength bands.