JDSU COSA-4055 CWDM Spectrum Analyzer Module For T-BERD 2000 COSA4055

JDSU COSA-4055 CWDM Optical Spectrum Analyzer
The Viavi Solutions® COSA-4055 module offers a new generation of coarse wavelength division multiplexer (CWDM) analyzers. Until now, large and expensive optical spectrum analyzers (OSA) were used to precisely test wavelength and power levels in CWDM networks, and optical channel checkers were used to verify optical channel presence. The Viavi COSA-4055 module offers the functionality and speed of an OSA in a handheld form factor at a fraction of the price.

Testing CWDM Networks with a COSA-4055 Module

CWDM Multivendor Compatibility
The ITU-T G.695 recommendation promotes vendor interoperability by specifying transmitter/multiplexer characteristics at one end of the CWDM link and the demultiplexer/receiver at the other end. ITU-T G694.2 recommendation specifies the spectral grid for CWDM applications with 18 channels from 1271 to 1611 nm, with a 20 nm channel spacing. To guarantee multivendor compatibility it is important to verify the optical interface parameters according to these recommendations. The COSA-4055 is the ideal tool for checking the critical parameters such as Tx output power and Rx input power and the central wavelengths when installing, commissioning, and troubleshooting CWDM networks as well as for ensuring interface compatibility with different vendors.

Transmitter Wavelength and Output Power
In CWDM networks, transmitter lasers are not equipped with a cooling system, thus temperature variations can cause a drift of the central wavelength and the power level. Every channel wavelength must be checked to verify possible wavelength shifts or power loss. The COSA-4055 module can determine the compliance to the CWDM system specifications.

Mux/Demux/OADM
Transmitters with a wavelength offset can create additional attenuation in the multiplexers and demultiplexers. When test access points are available, technicians can check a wavelength’s presence and its associated power level to verify that all transmitted wavelengths have been correctly multiplexed without excess power loss on one of the channels.

Receiver Wavelength and Input Power
Similar tests like those conducted at the mux/demux must be performed to verify channel wavelengths and power levels. A wavelength drift in the transmitter can also create power drift which can cause bit errors; therefore, it is important to monitor the evolution of channel power and wavelength over time.

Continuity
The pluggable SFP transceivers in the COSA can be used to test the link between the headend and the end customer, when a system transceiver is unavailable. It is important to verify the link loss per wavelength and guarantee the continuity of the connection over multiplexers, demultiplexers, and optical add-drop multiplexers (OADMs).

OSNR Testing
CWDM networks are for shorter-distance applications that do not require amplified links, thus enabling the use of a wider transmission window between 1270 and 1610 nm where amplifiers are unavailable. In non-amplified passive CWDM links, the OSNR remains unchanged on both the transmitter and receiver sides, eliminating the need to measure OSNR.

Ease of Use
One-button auto-testing guarantees that technician needs no special training to carry out a CWDM test, making Viavi’s instrument suitable for both novice and expert technicians. An Auto-Test mode automatically identifies WDM channels, selects the appropriate wavelength range, and provides auto scaling and system qualification according to pre-defined parameters.

Flexible Measurement Capability
In-depth analysis, featuring statistical, continue or single evaluation with automatic storage capabilities, is provided. Different measurement functions such as automatic channel detection, and pass/fail analysis against user-settable limits are available on the COSA-4055.

Furthermore, its tunable channel grid allows not only to measure according to the ITU-T G.694.2 CWDM wavelengths but also to use your own customized grid.

High Performance CWDM Testing
Full wavelength range 1260 to 1625 nm (Full band CWDM tester) Fast scanning speed (<4 s) Real spectral measurements with:

• Complete spectral trace
• Tabular results of power and wavelength
• Zoom and marker functions

Drift Measurement for Wavelength and Power
For optical performance monitoring it is essential to measure the key parameters over time. The built-in drift test application provides the result of power and wavelength over a customer definable time in a graphical and numerical format. Drift measurements are important in CWDM networks with uncooled laser, which have a typical wavelength drift of 0.1 nm/°C.

SFP Slot for CWDM Transceivers
The COSA-4055 provides an integrated SFP slot to host up to 2 SFP CWDM transceivers. The transceivers can be used to simulate CWDM transmitters for testing insertion loss per wavelength, and end-to-end continuity of a link in CWDM networks with mux/demux and OADMs.

Specifications