Performing Measurement Scans
50
CT440
Performing Line Wavelength Measurements
Performing Line Wavelength Measurements
Line wavelength measurement is only available for CT440 SMF models with two or more
TLS inputs.
CT440 featuring two or more TLS inputs include a powerful heterodyne detection system: it
detects precisely when the source of an input port crosses the wavelength of the source
connected to the next input.
Multiple Lines Measurement
The CT440 benefits from the heterodyne detector to allow the detection of multiple spectral
lines on one port.
The
Line detection
tab provides the list of all spectral lines detected during the scan in a
table. This allows you to use the CT440 as a multi-source wavemeter. It is possible to detect
up to 16 spectral lines.
Single Line Measurement
The heterodyne detection is useful if two or more TLS are used to perform a scan.
In that case, the sources are connected to two adjacent ports. Both sources are active.
While one source is sweeping, the second source waits until the wavelength of the
sweeping source coincides with the wavelength of the idle source before taking over the
sweeping. At this moment a signal is detected.
It provides a very accurate way to know precisely the wavelength at which a sweeping
source crosses the wavelength of the idle source.
This allows to verify how well referenced the TLS sources are and to correct the
measurement if one of the sources does not fulfill the performance specifications.
Limitations
The heterodyne detection is provided here as a powerful tool to enhance the
applications of the CT440. Nevertheless, the input optical ports are not specified here in
term of polarization whereas the heterodyne signal comes from the interference
pattern of two independent signals from two adjacent input ports. This interference
signal is optimal if the two sources arrive in the detector with the same polarization but
could be not detected if the two polarizations are orthogonal.
If the power of both sources (line power) is over 0.2 mW, the detection occurs in most
configurations.
If this tool is strongly required in your application, it is recommended to check first that
the spectral lines are well detected at the required power level and then leave the
inputs setup unaffected during all the measurement period.
Summary of Contents for CT440 Series
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