**4. Need for elastic optical node in optical fiber communication**

Recent developments in optical networking have enabled elastic allocation of spectral resources in a gridless manner in order to accommodate high-speed and variable-bitrate signals and achieve high spectral efficiency [41]. For instance, in [42] the spectrum sliced elastic optical path network centered on OFDM, alters signal bandwidths by changing the number of sub-carriers in the transmitted OFDM channel. Other elastic networks based on single carrier (SC) adapt the transmission modulation format in order to mitigate losses or transmit at higher data-rates by exploiting the high OSNR margin [8] with a tradeoff between transmission range and spectral efficiency (SE). Such demonstration requires optical communication infrastructure with the suitable functionality in order to operate [8], frequency/time/space multiplexing, spectrum defragmentation, wavelength conversion, multicasting, format conversion, etc. However, it would be costprohibitive to deploy a complete set of technologies and infrastructure to fulfill the requirements for all possible signals and traffic profiles. Instead, emerging technologies need to co-exist with existing ones and provide a smooth migration path where old technology can be gradually replaced. Also, in the context of dynamic optical networks the required services functionalities might change overtime as channels with specific transport and switching requirements are setup and terminated. Providing efficient support for this combination of dynamic requirements with static optical node architectures is a major challenge, which may not be achievable or cost effective [8]. Thus, a new type of flexible and evolvable optical infrastructure needs to be developed in order to enable flexible allocation of resources, and provide any switching and processing capability on demand.

The network scenario considered herewith takes into account the potential applicability of all-optical processing techniques in the network domain. **Figure 5** depicts a case within this framework which consists of four stages which can be placed in diverse geographical sites, i.e. arbitrary input traffic 12.5/42.7/170.8/Gb/s transmitters (WDM domain), an all-optical processing node, field transmission (dark fiber) and receiver. Upon entering the all-optical processing node and to

*DOI: http://dx.doi.org/10.5772/intechopen.88354 All Optical Signal Processing Technologies in Optical Fiber Communication*

**Figure 5.**

*Network scenario and switching node architecture. Four network sections are highlighted: transmission, all-optical processing in flexible architecture adaptable node (FC, format conversion; WC, wavelength conversion; WS, WaveShaper; MC, multicasting; OXC, optical cross connect), dark fiber, receiver [7].*

deliver the optical routing function, all the WDM signals are routed through the 96 × 96 3D-microelectromechanical systems. The optical cross connect architecture consist of subsystems such as Quad Semiconductor Optical Amplifier-Mach-Zehnder interferometer, 200 ms LCoS based SSS [43], wavelength/waveband AWG, (De)-Multiplexer, optical power couplers/splitters and EDFA are interconnected using a 96 × 96 3D-microelectromechanical systems optical switch. The grooming node delivers required real time all-optical processing [44] functionalities, arbitrary spectrum switching and time-domain sub-wavelength switching [45]. It also considerably improves the efficiency and elasticity of the optical node and offers support for current and future data-rates with transparent facilities with low power consumption. All the traffic after node is routed over a dark fiber link, and performances are evaluated by means of BER measurements [7].
