Language Reference

INSTMODE

limited in order to select wide bandwidth and fast settling characteristics. One example of using this mode is measuring the signal-to-noise ratio (SNR) of EDFA systems by measuring the ampli￿ed spontaneous emission (ASE) level immediately (10 ￿s) after the modulation is turned o￿.

W A R N I N G

In PRESEL, SR, and PD modes, the input signal passes through the

monochromator and is emitted from the front-panel's MONOCHROMATOR

 

 

OUTPUT connector. The power at the MONOCHROMATOR OUTPUT

 

may be attenuated very little from the power being applied at the

 

MONOCHROMATOR INPUT.

 

 

￿

PRESEL (Preselector). The front-panel's MONOCHROMATOR INPUT and

 

 

MONOCHROMATOR OUTPUT connectors are enabled. Monochromator

 

 

and diode ￿atness correction data only are used. Since in this mode a

 

 

complete sweep is ￿rst taken in OSA mode to place a trace on the screen

 

 

that represents the expected output power, both monochromator and

 

 

photodiode correction data is used. In this mode, the optical spectrum

 

 

analyzer's monochromator can be used to preselect the input optical signal.

 

￿

SR (Stimulus-Response). The front-panel's PHOTODETECTOR INPUT

 

 

and MONOCHROMATOR OUTPUT connectors are enabled. Only

 

 

monochromator and photodiode ￿atness correction data are used.

 

￿

PD (Photo-diode Test). The front-panel's MONOCHROMATOR INPUT,

 

 

MONOCHROMATOR OUTPUT, and PHOTODETECTOR INPUT connectors

are enabled. In PD mode, a normalization sweep is ￿rst taken using correction data for the internal photodiode only. Measurements are then made without correction data being applied. Refer to the following information when making a PD test:

1. Connect a jumper between the MONOCHROMATOR OUTPUT and the

PHOTODETECTOR INPUT.

2. Send the STORREF THRU command to store the light source ￿atness value in trace B.

3. Connect the MONOCHROMATOR OUTPUT to the device-under-test and the diode output to the rear-panel TRANS-Z INPUT.

4. Send the PDMEAS ON command to subtract the light source ￿atness (trace B) from the detected signal in trace A.

5. The normalized trace results are the diode responsivity where 0 dBm = 1 A/watt.

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