The Current Trends in Fiber Optic Communication Systems

The current phase of fiber optic communication system is considered to be the fifth generation system. In the current development phase is marked by multiple directions in the evolution of fiber optics. Researches to increase the capacity of optical fibers is going on in one side. Today, there was a news that the university of Illinois researchers reported their success and a record in fiber optic data transmission by delivering 57Gbps of error-free data at room temperature.

By transmitting more and more channels through the Dense Wavelength Division Multiplexing technique in the C-band and by reducing the channel spacing, commercial terrestrial fiber optic systems with the capacity in terabits per second are available today.

There is a trend to deploy the optical channels not only in the C-band, but also in the short wavelength S-band (1 460-1 530 nm) and in the long wavelength L-band (1 565-1 625 nm). Use of these multiple windows combined with the transmission using Dense wavelength division multiplexing opens the door for huge data transmission over optical fibers. The Raman amplification technique could be used for signals in all three wavelength bands.

Low water peak fiber complying with ITU-T G.652.D recommendations is available that can be used for transmission from 1260 nm to 1625nm. The whole range of the spectrum can be used since this fiber offers lower attenuation at the water peak region, which is at 1383nm. Availability of such fibres and new amplification schemes may lead to lightwave systems with a larger number of WDM channels on a single optical fiber. Coarse Wavelength Division Multiplexing technology make use of Low water peak fibers. More than 90 percent of the singlemode fibers used in optical fiber cabling are said to belong to the Low water peak fiber category.

Many experiments used channels operating at 40 Gbit/s in 2000. The trend had shifted to 100Gbps in 2006. The coherent technology introduced to deliver 100Gbps discards the problem of Polarization mode dispersion. PMD has been an issue on current systems but coherent technolgoy overcomes this issue. Experiments have been progressing to reduce the number of expensive optical/electrical/optical conversions within the optical transport networks (OTN).

There are two main reasons for the reduction in the number of optical/electrical/optical conversions. First, the DWDM systems are becoming more and more capable of carrying light signals for thousands of kilometers without electrical regeneration and that photonic cross-connect (PXCs). Second, the optical add-Drop multiplexers (OADMs) are available with the capacity, space requirements, power consumption, reliability and cost, suitable for their use in the telecommunication networks.

The use of multiple Optical/Electrical/Optical regenerators at a cost comparable to that of an optical amplifier is also a trend in the current fiber optic communication systems. Demonstrations of 400Gpbs and 800Gpbs transmission are becoming common these days. The Optical/Electrical/Optical regenerators could be put practically in all the nodes of the network. The additional cost could compensate the technical problems related to the implementation of an AON (impairments accumulation, network planning rules, optical monitoring, etc.)

Another trend is in the Access network region. ITU-T had approved recommendations in the next generation passive optical networks to deliver 10Gbps to the subscribers. The NG-PON2 standard is aimed to deliver 40Gbps speed from the central office and a speed of 10Gbps to the individual subscriber.

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Author: Prakash

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