OPM400

PRINCIPLES OF OPERATION The OPM400 measures optical power in the pW to mW range via a photodiode. Precision single ended transimpedance input stages provide for low offset and high linearity throughout the full dynamic range. The OPM400 has optionally 4 or 16 gain ranges. The switch is a semiconduc ...Read more

The transimpedance amplifier OPM400 is
designed for precise measurement of optical
power, from pW to mW. The output is
a voltage linearly proportional to the
input power.

The gain of the OPM400 may be controlled
via USB or the hard-wire interface control.
A graphical user interface is delivered with
the amplifier.

CHARACTERISTICS

Interfaces: USB and hard-wire (DB25)
Rise time: 1µs (G≤5x10^5); 4µs (higher gains)
Noise equivalent power: 500 pW(RMS) 
Gain control: 16 gain ranges in 1-2-5 pattern
or 4 gain ranges in decade spacing



PRINCIPLES OF OPERATION

The OPM400 measures optical power in the pW to mW range via a photodiode.

Precision single ended transimpedance input stages provide for low offset and high linearity throughout the full dynamic range.
The OPM400 has optionally 4 or 16 gain ranges. The switch is a semiconductor device, free from degradation.
The analogue output signal is available at the BNC connector on the front panel an on the appropriate line on the interface port on the back panel.

The voltage generated is then converted to a digital value via a 12 bit A/D converter. This process and all calculations and communication with the PC are controlled by a microcontroller. The measurement process is started via a command over the USB interface (software trigger). Alternatively, a continuous measurement stream can be started which samples at 1.5 kS/s. The measured photocurrent may then be read out from the USB port.

FIELDS OF APPLICATION

These optical power monitors are particularly useful for the linear measurement and monitoring of optical power. The fast response time at high signal-noise-ratio makes the OPM400 series particularly useful in systems control feedback loops, such as in fibre alignment systems. The high sensitivity and wide dynamic range allow measurement of fibre coupled lasers and LEDs alike.

Several options of photodiode material and optical input, make these units useful in a wide range of applications including non-telecom metrology.

These amplifiers have a particularly high sensitivity and large dynamic range. There are 16 gain ranges covering 5 decades of gain in a 1-2-5 pattern. The gain-to-gain accuracy of <1% allows confident measurements of power curves over the full range of sensitivity of the device: 6½ decades of measurement range. Thus even very demanding measurements such as the accurate and high speed, real-time determination of polarization extinction ratio becomes a simple task.

The OPM400 series is insensitive to electromagnetic interference by design, an important factor when working in "dirty" industrial environments. These units are provided in OEM-style enclosures. The case wings provide for mounting on standard 25mm and 1" optical table tops and for OEM applications.


• Detector: UV-Si, Ge, InGaAs, x-InGaAs, V-InGaAs

• Input receptacle: FC-receptacle, SMA-receptacle, free beam

• Number of gains: 4, 16

• Case: gull wing, lab style, 19" rack module

• Number of channels: 1, 2, 3, 4


Manual gain switch dongle for hardwire interface.


What are xInGaAs and V-InGaAs detectors?

These are two variations on the standard InGaAs (Indium-Gallium-Arsenide) photodiode.
The xInGaAs type has extended IR sensitivity out to 2100nm useful wavelength range. The short wavelength cut-off is the same as standard InGaAs.
The V-InGaAs type has extended visible range sensitivity down to 400nm useful wavelength range. The long wavelength cut-off is the same as standard InGaAs.

What is a "free beam" input receptacle?

By "free beam", we mean that the photodiode is openly mounted on the front plate of the unit. This is to allow measurement of free beams (not fibre coupled). This configuration may be inconvenient since the amplifier must be mounted directly in the beam path. If you wish to have a remote detector head then use the TZA500 (transimpedance amplifier) instead to measure the current from the remote photodiode.

What does an output impedance of 50Ω mean?

The output impedance of an amplifier is an important factor when dealing with fast signals. The speed of the OPM400 is fast enough for this parameter to be relevant. Essentially, the output of the amplifier is a 50Ω resistance in series with the output. This allows you to terminate the signal line with a 50Ω resistance to prevent back reflections. The result is a clean signal transient without overshoot. The disadvantage is that the signal voltage is halved by doing this. The amplifier may be used without the 50Ω termination resistance, but then there will be overshoot when amplifying fast transients.

Spezifikationen OPM400