The PDM-IR can be used either in gated or in free-running mode. Both modes of operations can be optimized through the use of several user selectable parameters, all controllable from a computer using either the delivered SDK library or the provided Windows® PC software.

When used in gated mode, the TRIGGER GATE signal, for GATE frequency generation, can be provided either using an INTERNAL TRIGGER or through an external signal fed into the TRIGGER IN input. Complex external trigger patterns can be also fed to the TRIGGER IN input, since it accepts not only periodic but also aperiodic signals. Additionally, it is possible to create even more complex patterns for GATE generation, by combining the auxiliary input AUX IN signal with the INTERNAL TRIGGER or the TRIGGER IN, and by using the provided user-selectable logic. Finally, the GATE signal can be generated either by exactly replicating TRIGGER GATE or by creating a new signal, synchronized with the rising edge of TRIGGER GATE and with a programmable fixed gated-ON width.

When used in free-running mode, the SPAD is always on until a SPAD avalanche is initiated. In this case, the avalanche current is first quenched and then, after a well-defined programmable hold-off time, the detector is immediately enabled.

Concerning the SPAD parameters, hold-off time, excess bias voltage and SPAD temperature, are all user selectable to allow the user to find the best trade-off for his measurement.

Concerning the outputs: PHOTON OUT is the low timing jitter output signal, precisely marking the photon detection time; signals on NIM AUX OUT and TTL AUX OUT can be chosen independently among TRIGGER GATE, INTERNAL TRIGGER, VALID GATE, PHOTON OUT and HOLD OFF signals.

The module has also internal counters, with programmable integration time, which continuously monitor the following signals: TRIGGER IN, AUX IN, INTERNAL TRIGGER, PHOTON OUT and VALID GATE.

All the main signal paths in the PDM-IR have a programmable delay, designed to help the user in synchronizing various signals both internally and with external instruments. This feature is very helpful in many cases, eliminating the need for constant adjustments to external cable lengths.

Fiber versions of PDM-IR are offered in two different mechanical enclosures: Desktop Instrument (DI) and Small Form Factor (SFF) version. To counteract the black body radiation of the SPAD package, which increases the dark counting rate of the detector, the DI version has an additional thermal loop that cools it down. Additionally, the fiber is protected inside the instrument and can be accessed through the FC/PC barrel on the front panel. The SFF version has the fiber pigtail exposed, and does not have the additional thermal loop. For this reason, DCRs in the SFF module depend on case temperature.

At MPD, a technical contact is always available for discussing with customers how to exploit at best the MPD technology in order to obtain the most accurate scientific results from their experimental set-ups.