Detectors

This page covers Luna detection modules (a line originally developed under the General Photonics brand) — compact photodetectors and building blocks for detection paths in measurement setups and OEM systems. The core of the offering are the BPD-series balanced detectors, which subtract the signals from two matched photodiodes to suppress the common-mode component (including source intensity noise) and extract weak interferometric signals — hence their use in OCT and coherent detection. The offering is complemented by polarization-diversity detectors, a fast in-line polarimeter and a fiber-optic Mach–Zehnder interferometer serving as an optical frequency discriminator.

Applications

Optical coherence tomography (OCT)
Coherent and heterodyne detection in measurement setups
Fiber-optic sensors and interferometric measurement systems
Monitoring of the state and degree of polarization in optical paths
Laser characterization, including optical frequency change measurements
OEM integration in measurement instruments and industrial systems

Key parameters

Parameter	Value
Module	Description
BPD-002	Laboratory balanced detector in a compact housing; balanced RF output (bandwidth up to 200 MHz) and power monitoring ports
BPD-002-OEM	Miniature AC-coupled balanced detector for OEM integration
BPD-003	Low-noise DC-coupled balanced detector for OEM applications
PBPD-001	Polarization-diverse balanced detector — independent analysis of the two polarization components of the signal
PDD-001	Polarization diversity detector: high-extinction-ratio polarization beam splitter with matched photodetectors
POD-001	Fast in-line polarimeter — simultaneous measurement of degree (DOP) and state of polarization (SOP)
MZI-001	Fiber-optic Mach–Zehnder interferometer for detecting optical frequency changes

Balanced detection in practice

In a balanced detector the optical signal reaches a pair of matched photodiodes, and the output is the difference of their photocurrents. Common-mode components of both channels — including source intensity noise and background — are suppressed, so the circuit achieves a much better signal-to-noise ratio than a single photodiode. This is the standard receiver architecture in interferometry, OCT systems and coherent links. The OEM versions (BPD-002-OEM, BPD-003) simplify embedding the module directly into the end device. Parameters of individual models (bandwidth, responsivity, wavelength range) are provided in the datasheets — ask for documentation.

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