Multi-parameter, multi-channel testing


ECOC 2002 preview

Optical component manufacturing can be simplified with a modular, multi-parameter swept-wavelength test system that measures all channels in parallel.

By Dan Daly, Business Development Manager PerkinElmer Optoelectronics

As the number of channels in DWDM components increases but revenues drop, optical component manufacturers are having to review their measurement strategies and evaluate all opportunities for removing cost from the production process.

PerkinElmer Optoelectronics have been producing telecoms test equipment for over 15 years and is now addressing component testing with a new system, the OCT8000. This instrument can simultaneously measure group delay, chromatic dispersion, differential group delay (polarisation mode dispersion), polarisation dependent loss and insertion loss in up to 256 channels of an optical component. This range of measurements addresses not only current needs but also the parameters becoming more important as 10 and 40Gbit/s systems lead to dispersion performance being a major concern. Return loss is also an option.

Not only can multi-channel devices such as arrayed waveguide gratings (AWGs) be fully characterised but also many single-channel components can be measured in parallel. This is particularly important where many measurements must be repeated at different temperatures.

This functionality is achieved with a new measurement method that is a variation on the well proven Modulation Phase Shift (MPS) technique. The optical intensity of the probe beam is modulated and the state of polarisation manipulated to give a range of states during the measurement, as in MPS.

The detection system and data processing techniques are new, however, and allow the required measurement parameters to be obtained together in one fast laser sweep. A major benefit is that the extra measurement channels do not add to the measurement time.

For future-proofing, the system uses a modular architecture that enables measurement channels to be added as required. A basic two-channel system can therefore be used initially, then more channels added. This could be because the channel count in the component has increased or the production volumes have grown and it is necessary to measure more components in parallel. Expandability delivers cost savings in the form of reduced requirements for further system integration and employee training.

Measurement is fast: just 3.5ms for each measurement point, and a full set of measurements covering the C and L bands in seconds. If required, there is the option to trade measurement speed for increased wavelength or measurement resolution.

To achieve the wavelength accuracy required when evaluating narrow-band DWDM components or broadband components with lots of structure, the OCT8000 has a built-in fast wavemeter with a wavelength accuracy of 1.5pm even in fast scanning mode. The inclusion of NIST traceable gas cells means that sub-picometer resolution is possible.

The user can select from a range of external laser sources, depending on the requirements of the application. If a laser is available there may be no need for additional lasers to be purchased.

Control can be performed either from the system itself (via the built-in computer with touch screen interface) or from a remote computer (via GPIB, LAN or RS232 connectors). Results can be presented in a variety of formats, including a simple pass/fail notice for use in production environments or a full set of graphical plots designed for experienced R&D users.

The OCT8000 is the first modular, multi-parameter, multi-channel swept-wavelength test system that addresses the measurement needs of optical component manufacturers.

Not only does its design enable components to be fully characterised in one sweep but its modular architecture offers a simple growth path as requirements change.

Dan Daly
Business Development Manager

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