What is a tunable DWDM Transceiver and how does it work?

by www.fiber-mart.com

We may ask why the tunable transceiver is available only for DWDM systems. That is happening because the frequency separation in CWDM systems is too wide in compared with the narrow band gap of DWDM systems. Dense wavelength division multiplexing (DWDM) refers originally to optical signals multiplexed within the 1550 nm band so as to leverage the capabilities (and cost) of erbium doped fiber amplifiers (EDFAs), which are effective for wavelengths between approximately 1525–1565 nm (C band), or 1570–1610 nm (L band).

 

Wavelength-converting transponders served originally to translate the transmit wavelength of a client-layer signal into one of the DWDM system’s internal wavelengths in the 1,550 nm band. Wavelength converting transponders rapidly took on the additional function of signal regeneration. Signal regeneration in transponders quickly evolved through 1R to 2R to 3R and into overhead-monitoring multi-bitrate 3R regenerators.

 

Around 88 different channels can be set with intervals of 0.4nm, which is the 50 GHz band. These optics usually start from channel 16 up to 61 but this depends on the manufacturer of the Router/Switch and which channels it supports.The wavelength is tuned by changing the filter wavelength.Tuning these optics can be done by us and some intelligent networking devices can do it for you. The transceivers can be used in various types of equipment such as switches, routers and servers from different vendors. These transponders are the spare batch for a given optical transmission system, they can replace a faulty fixed-wavelength transponder being tuned on their frequency by the embedded software and with an external operating software with either a laptop or API application.

 

Wavelength tunable optical transceivers are becoming important as components that enable ROADM  functionality in next-generation networks. These transceivers have the characteristic that their wavelengths can be switched between different DWDM channels while in use in the network. Channel switching capability has resulted in a reduction in the number of components and cost in today’s DWDM systems.

 

 

 

Form factor:

 

Tunable XFP transceivers

Small Form Factor 10Gb/s XFP transceiver complies with the XFP Multi-Source Agreement (MSA) Specification. It supports amplified DWDM 10Gb/s SONET/SDH, 10 Gigabit Ethernet, and 10 Gigabit Fibre Channel applications over 40km of fiber without dispersion compensation. These transceivers are capable of speeds of 10Gbit/s and have up to 80Km reach in a combination of optical components and optical fiber attenuation.Digital diagnostics functions are available via a 2-wire serial interface, as specified in the XFP MSA.

 

 

The SFP+ tunable transceiver

This form factor allows network equipment manufacturers to reduce the size and power consumption for 10G connections while supporting the network operators rapidly increasing capacity needs driven by data-heavy network applications.

 

Tunable SFP+ module is a high performance tunable pluggable transceiver for use in the C-band window covering 1528 nm to 1566 nm. The module supports data rates from 9.95 Gb/s to 11.3 Gb/s and is provided in an SFP+, MSA compliant package. The reach may be up to 80 km link lengths on 9 μm singlemode fiber.

 

One important feature of tunable transponders is the hot-swappable functionality which allows a quick restoration for a faulty fixed transceiver.

 

The next step is to develop a higher-performance tunable transceiver to satisfy the 100G systems. As the core of tunable transceivers, tunable laser requires higher power, a wider tuning range, and lower power consumption. In addition, the package of the next generation tunable transceivers must be more and more compact to meet the aggregation switches.

 

Advantages summary

Flexible network management. A tunable SFP+ transceiver will be remotely configured for a specific wavelength to support bandwidth changes as needed in Enterprise or Metro networks.

Reduced network inventory. One tunable SFP+ transceiver will support more than 80 different wavelengths. It will allow network operators to hold one tunable device code as opposed to 80+ fixed wavelength transceivers.

Reduced power consumption. It will provide a significant reduction in electrical power dissipation compared to other tunable solutions.

Compact and high-density form factor. The new tunable SFP+ transceiver will be about the size of a pack of gum, saving valuable real estate in data centers.

Increased network capacity. The tunable SFP+ will double the number of channels supported in this compact transceiver form factor. Upgrading to 50 GHz channel spacing doubles the capacity potential in Enterprise and Metro networks.