CWDM

Traditionally, each data service – including digital telephony – implemented in organizations has involved the deployment of specific new transport infrastructure. Most times, this new infrastructure involves significant expenses for renting optical fiber, drawing out the cycles needed to generate a return on the investment.

Technologies like DWDM and CWDM, through optical multiplexing, allow different data channels to be integrated on a single fiber-optic pair.  This means that a single fiber can transport multiple services. CWDM (Coarse Wave Division Multiplexing, G.694.2 of the ITU-T) defines 18 wavelengths separated by 20nm in the O, E, S, C, and L optical bands. Each one of the optical carriers offers an independent optical channel over which any service can be carried: SDH, TDM, ATM, Gigabit, 10Gigabit, FiberChannel, and FICON, among others. This gives it a high level of flexibility and security in the development of campus, metropolitan, and regional optical networks.

Currently, to make efficient use of conventional G.652 single-mode fiber, most CWDM products work on the 8 carriers in the S, C, and L bands (1470nm, 1490nm, 1510nm, 1530nm, 1550nm, 1570nm, 1590, and 1610nm).

TELNET’s CWDM Solution: MetroSAE

The MetroSAE chassis is the central element in TELNET’s CWDM solution. This chassis supports two multiplexers and 12 optical adapters. The optical adapters are responsible for situating a particular service, which the user delivers to the MetroSAE, on a CWDM wavelength, later entering the optical multiplexer.

TELNET’s extensive catalog of optical adapters includes the following services:

• E1
• E3
• Gigabit Ethernet
• 10GbE
• SDH in STM-1, STM-4, STM-16, and STM-64 hierarchies,
• FiberChannel 1G, 2G, 4G, and 10G
• ESCON
• FICON
• DVB-ASI digital video

TELNET’s CWDM solution is completely modular, allowing all components to be hot-swapped in and out. Thanks to the use of standard GBIC, SFP, and XFP modules, this level of modularity extends to all of the laser optics used. This flexibility provides significant benefits in maintenance tasks and in the costs associated with spare parts.

The MetroSAE’s advanced architecture offers powerful tools and utilities to carry out preventive maintenance tasks. The unit monitors parameters in real time, including the temperature of each laser, polarization currents, and optical power transmitted and received.  This way, the technical team in charge of management can identify operational anomalies and even predict future malfunctions 

TELNET’s different CWDM solutions can be managed remotely via IP and SNMP. Using the management console, it is possible to get detailed information on the status of all of the elements in the chassis. Among other possibilities, this tool allows access and management of alarms, event logs, realistic display of equipment status and simultaneous configuration of a particular number of units with other consoles like HP OpenView SA, Orchestream, etc. 

Differences between CWDM and DWDM

CWDM and DWDM share the same technological concepts of optical multiplexing. The only difference is in the number of lambdas that are used in DWDM and the separation between them. In CWDM, lambda separation is 20nm, in DWDM this separation varies between 0.8nm and 1.6nm, depending on the operating band. This requires the DWDM laser to be stable, and to maintain this precision, it has to operate within a particular range of temperatures so that the transmission frequency does not vary.

TELNET’s solution makes hybrid CWDM-DWDM configurations possible. In these solutions, a CWDM and DWDM coexist in the same optical node. The DWDM multiplexer would operate on spectrum reserved for the C and L bands, situating 8 DWDM channels per CWDM channel. These hybrid configurations permit migration towards DWDM. This evolution protects part of the initial investment, since the chassis, power supply system, management, and all of the optical adapter modules are maintained. Only the multiplexer and CWDM optics based on standard GBIC, SFP, and XFP need to be replaced.