Features of the EnvCalc toolbox

EnvCalc is a toolbox of routines running under MATLAB® that processes waveforms from a real-time sampling oscilloscope. Starting from saved raw measurement files, it calculates the information bits on the optical signal, together with the bit error rate and Q factor, and can display the signal graphically in a multitude of ways.

The EnvCalc toolbox can be put to use quickly by anyone with moderate knowledge of MATLAB.

· Built-in help text for each routine

Help text includes explanation of the function, plus details of all input and output parameters

· Comprehensive error checking

Error messages and warning messages to catch inadvertent coding mistakes by the user, each providing advice on which parameters to correct.

EnvCalc includes the following functions:

· Calibration of the passive optical mixer

Determines phase angle and path length difference between outputs of hybrid.

· Clock recovery

Finds clock for binary & quaternary formats, including the case when clock frequency is not related to sampling rate by a rational multiplier.

Retimes signal to give a sequence of complex values corresponding to symbol centres.

Processes signal seamlessly in blocks to avoid memory overflow when measurement burst is long.

· Phase estimation

Recovers the optical phase of the signal and applies phase correction.

Phase estimate is near theoretical limit in terms of tolerance to phase noise – works with DFB lasers.

· Match signal values to pseudorandom bit sequence

PRBS recovery works in presence of bit errors & cycle slips.

Support for wide range of pseudorandom sequences, including all standard sequences.

· Count bit errors

Counts errors for binary and quaternary formats.

Separates bit errors from cycle slips, and reports them independently.

· Q-factor

Calculates decision threshold Q-factor or simple (histogram based) Q-factor.

· Adaptive equalisation

Can be used to set filter coefficients to optimise a given parameter, e.g. Q-factor, to obtain best possible receiver frequency response.

without equalisation

with equalisation

· Graphical output

Produces several graphical representations of measured data: phase diagram, eye diagram, etc.

EnvCalc will run on a Macintosh, PC or workstation, provided MATLAB is already installed. For more information click here.