Optical Power Meter OPM200 » Artifex Engineering

The optical power meter OPM400 is designed for precise, high speed measurement of optical power in the nW to mW range. The output is a voltage linearly proportional to the input power.

The gain of the OPM400 is controlled via a hard-wire interface on the back panel.

Characteristics

Interfaces: Hard-wire (DB25)
Rise time: 1µs (G≤5×105); 4µs (higher gains)
Bandwidth (-3dB): 350kHz
Noise equivalent power: 0.5nW
Gain control: 16 gain ranges in 1-2-5 pattern or
4 gain ranges in decade spacing

Description

PRINCIPLES OF OPERATION

The OPM400 measures optical power via a photodiode. Photodiodes are useful for power measurement in the visible and near infra-red due to their inherent sensitivity and speed of measurement.

Photodiodes produce a current which is proportional to the incident light power over a wide dynamic range. The disadvantage when compared to calorimetric devices is the wavelength dependance. However, for use with monochromatic sources, the detector can be calibrated and the measured current corrected accordingly.

The current from the photodiode is converted to a voltage through a precise transimpedance amplifier. This amplifier is very linear over the full measurement range of the device.

The OPM400 amplifier employs high quality photodiodes and precision transimpedance input stages to provide for low offset and high linearity throughout the full dynamic range.

FIELDS OF APPLICATION

This optical power monitor is particularly useful for the measurement of fibre coupled sources. The output is a voltage linearly proportional to input power. The fast response time at high signal-noise ratio makes this OPM series particularly useful in systems control feedback loops.

The high sensitivity and large dynamic range allow measurement of a wide range of optical sources such as lasers and LEDs alike.

The OPM400 series is insensitive to electromagnetic interference by design, an important factor when working in “dirty” industrial environments.

These units are provided in a modular 19“ rack mount system.

Specifications

Parameter	Conditions	Si, InGaAs	Ge	Units
Input
Power ranges (full scale)	Maximum range Minimum range	4.5 (typ) 45 (typ)	45 (typ) 450 (typ)	mW nW
Noise equivalent power (NEP_RMS )	Range: 4.5mW Range: 45nW	2.5 (max) 0.5 (max)	25 (typ) 5 (typ)	µW nW
Connectors		FC, SMA or ST	FC, SMA or ST
Output
Function		Linear analogue : V_out = scale x I_in
Output range (full scale)		3.7 (min)	3.7 (min)	V
Output scale with 16 gain range option	Range: Si, InGaAs 4.5mW-45nW Ge 45mW-450nW	1 (typ) 0.1 (typ)	0.1 (typ) 0.01 (typ)	V/mW V/nW
Output scale with 4 gain range option	Range: Si, InGaAs 4.5mW-450nW Ge 45mW-4.5µW	1 (typ) 1 (typ)	0.1 (typ) 0.1 (typ)	V/mW V/µW
Connectors		BNC and DB25	BNC and DB25
Setting time (1%)	Source capacitance < 100pF	2 (max)	2 (typ)
Rise / Fall time (10% – 90%)	Source capacitance < 100pF	1 (max)	1 (typ)	µs
Accuracy		± 1 (min)	± 1 (min)	%
Output impedance		50 (max)	50 (max)	Ω
Logic
Current required for switching	HI=5V LO=0V	– 100 (min) 5 (typ) 100 (max)	– 100 (min) 5 (typ) 100 (max)	nA
Switching time		2 (max)	2 (max)	µs
Power supply
Type		Wall plug (supplied)	Wall plug (supplied)
Dimensions
	1 channel	103 x 106 x 116 (B x H x L)		mm
	4 channel	103 x 106 x 116 (B x H x L)		mm
	19″ rack modules	3U