Acterna provides jitter-free reference transmitter
November 23, 2004 Germantown, MD -- Test and measurement equipment provider Acterna today announced it has designed and manufactured a reference transmitter according to ITU-T O.172 Appendix VII, which exceeds the minimum accuracy requirements set by the International Telecommunications Union-Technology Standardization Sector (ITU-T).
November 23, 2004 Germantown, MD -- Test and measurement equipment provider Acterna today announced it has designed and manufactured a reference transmitter according to ITU-T O.172 Appendix VII, which exceeds the minimum accuracy requirements set by the International Telecommunications Union-Technology Standardization Sector (ITU-T). The Acterna reference transmitter generates a reference signal virtually free of pattern-dependent jitter and enables Acterna to provide standardized jitter receiver calibration and verification in the manufacturing process, resulting in increased receiver-to-receiver consistency and absolute accuracy, say company representatives.
Acterna and other test instrument vendors are working to develop consistency between their different instruments so that they do not report different jitter measurement results from the same device under test (See "Jitter gives ITU-T the shakes,"Lightwave, October 2004.) This consistency can only be guaranteed by a well defined, worldwide standard jitter source and an accepted standard jitter calibration method. To that end, Acterna is an active member of the ITU-T and has participated in the development of the ITU-T measurement recommendations since 1968. Acterna actively participates in several ITU-T Study Groups, including Study Group 4, which has been tasked with standardizing the performance of jitter measurement equipment.
Acterna's Appendix VII reference transmitter solution
Recently, the ITU-T proposed a new "Method for Verification of Measurement Result Accuracy and Intrinsic Fixed Error." This method will be formalized in the new ITU-T O.172 Appendix VII beginning 2005, and utilizes a high-quality optical data signal with the capability of adding pulse transient sinusoidal modulation. Acterna contends it is one of the first test instrument manufacturers to implement Appendix VII in both development and manufacturing. The existing ITU-T O.172 recommendation for jitter test sets defines fixed intrinsic error limits for jitter measurement receivers; however, this recommendation does not describe a method for verifying receiver accuracy. The only way to compare different jitter receivers is to compare them to a well-known jitter reference--a reference transmitter. As a result, Acterna will make a reference transmitter available to customers by way of its ONT-512 Optical Network Tester.
The reference transmitter in the ONT-512 will allow customers to verify jitter receiver equipment to a known source, resulting in greater consistency of jitter measurements from different test sets. The reference transmitter may also be used as a jitter-free reference data signal for DUTs. The pattern-dependent jitter of this reference transmitter is negligible, with a total jitter of less than 10 mUIpp (peak-to-peak) measured in bandwidth f1-f4. The new method, using a reference transmitter, will enable both test equipment vendors and users to accurately characterize jitter measurement equipment.
Appendix VII also defines recommended test parameters to ensure that a jitter receiver can measure all types of jitter, including transient and continuous jitter. The test parameters generate an accuracy map that defines the performance of an individual jitter receiver. The accuracy map makes it possible to compare jitter characteristics of different instruments and normalize the results, helping solve the problem of different jitter test sets giving different measurement results.
The reference transmitter is key to the O.172 Appendix VII recommendation. This reference source is used for jitter receiver calibration and verification of Acterna's ONT jitter products. Acterna will begin to offer an accuracy map option, providing jitter accuracy profiles plotted for each individual jitter receiver.
Acterna's Appendix VIII phase analysis solution
In addition to the reference transmitter, Acterna characterizes and verifies jitter transmitter accuracy using the newly adopted phase analysis method recommended in the ITU-T O.172 Appendix VIII draft and will offer a special transmitter option that will guarantee the jitter generation values of the transmitter on Acterna's ONT jitter products. Acterna will certify the intrinsic jitter of the ONT transmitter as a characterized known value.
Acterna's ONT-506/512 Optical Network Tester
Acterna's ONT-506/512 has the ability to measure the performance of thousands of VT/TU channels simultaneously, minimizing the performance risk associated with relying on a single test channel. The platform addresses the challenges of testing next-generation SONET/SDH grooming and switching performance, and its multiple ports allow the user to load/analyze line interfaces simultaneously. This elevated coverage helps achieve higher-quality results, as potential line card dependencies are identified.
The ONT-506/512, with its multiple channel and port test application as well as jitter and wander testing capabilities, meets the research and development requirements of both network manufacturers and operators by addressing all phases of the development of new network components, say company representatives.