DWDM Based Frequency Channel

DWDM Based SuperChannel

NS Khawaja Waleed IqbalNS Usman ShahidNS Alamgir Nasir

NS Musaub ShaikhGC M. Sami

What is DWDM?• Stands for Dense Wavelength Division Multiplexing• Multiplexing technique in which a number of carrier signals with

different wavelengths are multiplexed onto a single medium.• Used in Optical Fiber (long haul network)• Theoretically, 80 different (virtual)channels are possible in a single

channel.• Dense WDM is a type which multiplexes optical signals within

1550nm band.• Communication is bi-directional with a data rate of 2.5Gbps(approx)

What is DWDM? (cont.)

• Also called Wave Division Multiplexing.• DWDM is the answer of “fiber exhaust”.• Demand for internet services is growing 40% each year.• Lack of network engineers• A few papers were published regarding the capacity and service

provided by it.• These paper provided the physical

and engineering practicality.

Superchannel• An evolution in DWDM.• Several carrier waves are combined to create a composite line side

signal of desired capacity, brought into service in one operational cycle• The advantage, the achievable data rate is 1Tbps.• Increased high spectral efficiency and operational scalability.

Problems addressed by SuperChannel• Scaling bandwidth without scaling operational procedures• Optimizing DWDM capacity and reach• Supporting the next generation of high speed services

The most recent innovation that enables a practical increase in bandwidth with long haul reach is coherent detection

A primer on Modulation• A simple form of modulation called Intensity Modulation Direction

Detection(IMDD).• Encodes single bit in each symbol representing one cycle of a clock.• Optical fiber impairments(attenuation, non-linearity, chromatic

aberration etc) must be factored in network design.

Implementing SuperChannels• No finalized standards of currently exists.• Unresolved issues of number of carriers, data rates, level of

component integration.• Highly dependent on implementation decisions.• Should be able to answer all 3 issues discussed earlier

Transmitting more symbols

Two Drawbacks• First, electronics will also need to operate at 320 Gbaud.• This level of integrated electronics will not be available for next

decade.• Second is that the high symbol rate will encounter significantly higher

implementation penalty with today’s modulation type.

Key point

Both single carrier and super-channel implementations have about the same spectral efficiency, but the super-channel has far better optical

performance and it is possible to build it using technology that will be available in the near future.

Importance of Photonic Integration

The PIC enables hundreds of optical functions to be collapsed into two small chips the size of a fingernail enabling, in this example, 10 x 100 Gb/s in a single line card

Conclusion

Conclusion(cont.)• Technological advances allows an increase data rates to 100 Gb/s• These technologies will soon be close to their practical or theoretical

limits for an individual wavelength• Flexibility will be a key factor in super-channel architectures. A flexible

coherent modulation type is key to optimizing the combination of reach and spectral efficiency• Large scale photonic integration is a critical technology in producing

super-channel