IEC advances fiber-optic-system testing
BY DR. ANDRE GIRARD
Working Group 1 of the International Electrotechnical Commission's (IEC) SC86C took several steps to advance fiber-system testing at its May 13-14 meeting in London.
In IEC 61282-3, "Fibre optic communication system design guides, calculation of polarization mode dispersion," polarization-mode dispersion (PMD) is calculated for link penalty. Receiver tolerance to PMD is also considered at 40 Gbits/sec since receivers have a lot of internal components such as filters and compensators and consideration needs to be given on how they can be standardized.
In IEC 61280-4-4, "Test procedures for fiber-optic-cable plant and links, polarization-mode dispersion for installed links," new methods are considered. Polarization phase shift uses a modulated tunable laser and a polarization beam splitter for the measurement of the principal states of polarization over a wavelength increment and deduces the corresponding differential group delay. A modification of the Fixed Analyzer method was proposed based on the use of a tunable laser with amplified spontaneous transmission filtering. A new method, the Poincare Sphere Analysis is now under consideration for testing PMD on optical amplifiers. It will complement the Jones Matrix Eigenanalysis method. A technical report will be developed describing the mathematics of different methods and different implementations for different applications. Technical committee TC86 on Fibre Optics has a task force that produced a document describing PMD applications, test methods, and general information.
Test procedures for digital transmission systems were also reviewed during the meeting, such as IEC 61280-2-2, "Optical eye pattern, waveform, and extinction ratio," and 61280-2-8, "Averaged Q factor measurement." The latter does not need to extract the receiver clock information, is bit-rate-transparent, and as such is simpler than the conventional bit-error-rate testing.
A new test method on time-resolved chirp was introduced for transmitters. It reviews different modulation techniques, defines chirp, and describes three test methods: frequency discriminator, frequency-resolved optical gating, and monochromator.
Dr. Andre Girard, who is responsible for international standards at EXFO (Vanier, Quebec), represents the company in ITU-T SG15, IEC SC86B and SC86C, and TIA FO-6.3. He can be reached at tel: 418-683-0211; fax: 418-683-2170; e-mail: firstname.lastname@example.org.