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4-38 Example Programs
Example 5. Measure signal-to-noise ratio of each
WDM channel
This program measures signal-to-noise ratios on a WDM
system. It measures the ratio for each line using com-
mands from the CALCulate3 subsystem.
Refer to the introduction to this section for a descrip-
tion of each subroutine that is contained in this pro-
gram.
COM /Instrument/ @Mwm
ASSIGN @Mwm TO 720
DIM Key$[1]
ON ERROR GOTO Error_msg,
Set_ese
PRINT USING "37A,33A";"Multi-Wavelength Meter Identity is :
";FNIdentity$
ON TIMEOUT 7,5 CALL Err_mngmt
Cmd_opc("*RST")
OUTPUT @Mwm;":MEAS:ARR:POW:WAV?"
ENTER @Mwm USING "#,K";Nb_pt
ALLOCATE Current_wl(1:Nb_pt)
ENTER @Mwm USING "#,K";Current_wl(*)
OUTPUT @Mwm;":FETC:ARR:POW?"
ENTER @Mwm USING "#,K";Nb_pt
ALLOCATE Current_pwr(1:Nb_pt)
ENTER @Mwm USING "#,K";Current_pwr(*)
! Turn signal-to-noise ratio on
Cmd_opc(":CALC3:SNR:STAT ON")
Err_mngmt(":CALC3:SNR:STAT ON")
! Set first wavelength as noise reference
Cmd_opc(":CALC3:SNR:REF:WAV MIN")
Err_mngmt(":CALC3:SNR:REF:WAV MIN")
! Query number of data points
OUTPUT @Mwm;":CALC3:POIN?"
ENTER @Mwm USING "#,K";Nb_pt
ALLOCATE Snr_pwr(1:Nb_pt)
! Query signal-to-noise values
OUTPUT @Mwm;":CALC3:DATA? POW"
ENTER @Mwm;Snr_pwr(*)
OFF TIMEOUT
FOR I=1 TO Nb_pt
PRINT USING "7A,2D,17A,M4D.3D,25A,S2D.2D,22A,2D.2D,3A";"Line
: ";I;" wavelength is : ";Current_wl(I)/1.0E-9;" nm, absolute level is :
";Current_pwr(I);" dBm, with a SNR of : ";Snr_pwr(I);" dB"
NEXT I
STOP
Error_msg: !
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