Measuring Zero Loss; Measuring Insertion Loss - JDS Uniphase SWS15100 User Manual

Measuring Zero Loss

Before making measurements, the system characteristics, without a DUT, need to be
established. This process is known as zero loss referencing, or simply referencing. Zero loss
references must be performed whenever the fibers to the DUT, or from the DUT to the detector
module, are changed, moved, or cleaned. If the fibers are left essentially undisturbed, a zero loss
reference needs to be done only once a day. The measurement compensates for any optical
losses or wavelength dependence not due to the DUT. System specifications are based on a
reference made directly before device testing.
To make a good zero loss measurement:
1. Set up the fibers as if to test a device. Instead of connecting the DUT, connect the device
input and the channel input using the proper mating sleeve.
A zero loss measurement must be made before any measurement can be made using the
SWS. Occasionally, as in the case of measuring a fiber Bragg grating in reflection, the process
of zero loss referencing becomes more complicated (see the Example Application:
Characterizing Fiber Bragg Gratings in Reflection section).

Measuring Insertion Loss

The IL through all channels in a device can be measured quickly and easily as a function of
wavelength using the SWS. The wavelength ranges covered in C-band and L-band systems are
specified in the Specifications section, as are the measurement accuracy, repeatability, and
dynamic range.
To measure IL:
1. Set the source optics module to the required polarization state.
2. Select insertion loss mode.
3. Select the channels to process.
4. Perform a zero loss reference scan for each of the selected channels.
5. Connect the device.
6. In the SWS application, select the type of analysis to be performed.
7. Acquire a trace.
The insertion loss trace appears on the screen. To manipulate the screen image, zoom in or out,
pan, or select a window on which to zoom in.
92 – Operating and Maintenance Instructions
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