Signality Solutions

Electro-optics

Signality solutions has the knowledge and experience to help you design even the most challenging and innovative products

Expertise in several areas of electro-optical signal processing:

• high speed modulation and power control for Fabry Perot and Distributed Feedback lasers;
• high power pulse laser drivers;
• optical receivers using PIN and Avalanche photodetectors for;
• data and telecoms applications up to 10GBit/s;
• high dynamic range monopulse applications;
• precision optical signal detection and power measurement;
• modelling and simulation of electro-optical components and sub-systems;
• in-house creation of spice macromodels for a wide range of electro-optic devices including laser, PIN photodiode and APD, opto-isolator and opto-triac devices;
• CCD and CMOS imager and video signal processing.

As an example of the use of electro-optical modelling and simulation, the graph below illustrates the simulated performance of a combined precision optical power measurement and threshold detection subsystem. Modelling in this application included the laser driver, laser diode, fibre loss, PIN photodetector diode and associated transimpedance amplifier. 

A variant of this subsystem using an avalanche photodetector included simulation of a specilaised temperature compensated low noise switched mode supply. This also sucessfully implemented a unique solution to a problem of APD non-linearity with increasing input optical power that is poorly documented in literature about APDs.

Requiring only a single point calibration, both subsystems have been deployed right by design, in a number of products by a major networking company.

Another example of the successful use of simulation in electro-optic design was to solve a signal integrity problem where the output of a datacommunications laser exhibited severe ringing on the rising edge and multiple spikes following the falling edge. Simulation of the laser device and driver showed that there was no inherrent reason for this behaviour. However, adding the package parasisitcs for the particular type of laser used in this application clearly demonstrated a resonance between the device leads and the the package capacitance to ground. Splitting an existing damping resistor and moving it to an appropriate location in the simulation schematic showed that the ringing could be effectively damped out. Making this modification to the real circuit showed results in very close agreement with the simulation.

In this example, simulation of the circuit allowed a problem to be investigated - and prevented - that would not have been physically possible without a major undertaking since the resonant node existed inside the laser package and could not be probed externally. The only effect that could be physically observed was by measuring the optical output of the laser wich gave no insight into the underlying cause. 

• Simulation made it possible to look inside the package.

To see how Signality Solutions can help you and to discuss your requirements, just contact us.