Optical Channel Setup

Your module may have electrical channels, optical channels, or both. The dialog-box configuration varies depending on the available channel types. This topic provides information on configuring optical channels.

Click Setup > Modules > Channels X to open this dialog.

Click the channel button to display or hide the channel's waveform on the display.

When an 86115D Option 004 module is used, the Channel Setup dialog includes the Input Connector. This field allows you to select either input A or input B for the channel.

Scale sets the channel's sensitivity (Watts-per-division), with vertical expansion and contraction about the second graticule division from the bottom of the display screen.

A waveform's Offset is identified by a ground marker ( ). This marker is located on the display's right side, has the same color as the associated waveform, and identifies the location of 0W. Each channel has its own ground marker. The default marker position is two graticules down from the middle screen for optical channels. During an Auto Scale, an offset is applied to vertically center the signal. The offset changes the vertical position of the waveform on the display screen without modifying the waveform itself. The offset value represents an absolute value on the instrument display. The amount of offset applied is shown on the Channel button. You can also quickly change a waveform's vertical offset by using the pointing device to vertically drag the ground marker ( ) on the display.

 

Reference Filters

Reference Filters are used with optical channels for compliance testing. On some modules, there is a Filter On field that can be used to enable or disable the filter. For example, SONET/SDH, Gigabit Ethernet, and Fibre Channel standards have defined the compliance tests for consistency in standard measurements. These tests must be performed in a specific bandwidth. This bandwidth is achieved using the filters in the optical channels. The compliance tests then verify the performance of the input signal in that bandwidth. These filters concur with specific SONET/SDH, FC, or Gb En symbol rates. The filters available for the optical channels are dependent upon the type of plug-in module used to measure the input waveform.

Reference filter selections in the drop-down list include a value in parenthesis that represents the nominal system bandwidth (O/E amplifiers, samplers, and A/D conversion) for a chosen hardware filter.

Reference Filters and SIRC Data

Select SIRC (System Impulse Response Correction) to apply N1092A, 86105C, 86105D, 86115D, or 86116C module correction data (Option IRC). The correction data compensates for the optical module's specific response and ensures that the eye diagram will look more consistent between different modules.

• To learn about SIRC Data

Reference Filter for TDEC Measurement (86105D and 86115D modules)

For TDEC compliance measurements, the relevant standard calls for a specific reference filter to be used. Select the TDEC (12.6 GHz) filter in the Reference Filter drop-down list. This reference filter is not required unless you are performing a compliance measurement.

Wavelength Setting

Use the Wavelength field to select the calibrated wavelength for measurements. Optical channels use an internal photo detector to receive an optical signal and then convert this signal to an electrical signal. A conversion gain (factor) is used to accurately display the signal in optical power units. For example, 1 mW of optical power yields a 28 mV electrical signal. Optical channels are factory calibrated at a specific Wavelength to provide both accurate display of the received optical waveform in optical power units and measurement of the signal's average power.

• Refer to Optical Calibration to learn the calibrated wavelengths of individual modules. Optical channels have reduced bandwidth settings for improved noise performance.

You can also operate optical channels at a user-defined wavelength. The user-defined wavelengths must be within the wavelength ranges specific to each plug-in module. For example, if you are operating the 86101A module, you can select a user-defined wavelength between 750 nm and 860 nm.

Custom Waveform User Names

Waveforms displayed in tiled, stacked, or zoom tiled views include a waveform label. You can change the waveform's labels to your own more meaningful user name by clicking on the label in this dialog.

• To learn about custom labels

Waveform Color

Click the Color button to display the waveform in one of 16 colors.

External Hardware Scaling

Click External HW to compensate for an external transducer or external attenuator in the test setup. External hardware scaling is available for both electrical and optical channels.

Advanced Settings

Click the Advanced button to select the channel's Sampler Bandwidth, enter Horizontal Software Delay, and to select the signal type.

Optical Wavelength Regions

The following tables show wavelength bands and regions commonly used in the optical communications industry. The band and region ranges are listed for classification purposes, and do not necessarily imply specification of a given range.

Single-Mode Systems

Wavelength Band	Range
region II	1260 nm to 1360 nm
region IIe	1360 nm to 1480 nm
S-band	1440 nm to 1530 nm
C-band	1530 nm to 1565 nm
L-band	1565 nm to 1625 nm
M-band	1625 nm to 1675 nm

Multimode Systems

Wavelength Band	Range
region Im	770 nm to 910 nm
region IIm	1260 nm to 1380 nm

Copy From

Copies channels settings from a source channel. Copied settings include the following:

• Scale
• Offset
• Hardware Skew
• Software Delay
• Signal Type Auto Detect and Type
• External Transducer settings
• External Attenuator settings

The copied settings do not include waveform color or any custom waveform name.