Abstract
Directly modulated long-wavelength vertical cavity surface emitting lasers (VCSELs) are considered for the implementation of sliceable bandwidth/bitrate variable transceivers for very high capacity transmission (higher than 50 Gb/s per wavelength) in metropolitan area systems characterized by reduced cost, power consumption, and footprint. The impact of the frequency chirp measured for InP VCSELs with different kinds of design (high-bandwidth very short cavity and widely-tunable with micro electro-mechanical systems (MEMS) top mirror) is analyzed in case of discrete multitone (DMT) direct modulation in combination with 25-GHz wavelength selective switch (WSS) filtering. The maximum transmitted capacity for both dual side- and single side-band DMT modulation is evaluated as a function of the number of crossed nodes in a mesh metro network, comparing VCSEL based transmitters performance also with the case of external electro-absorption modulator use. Finally, the maximum reach achieved based on the received optical signal to noise ratio (OSNR) and the fiber span length is discussed. The results confirm the possibility to use directly-modulated long-wavelength VCSELs for the realization of sliceable bandwidth/bitrate variable transmitters targeting 50-Gb/s capacity per polarization, also in the presence of 5 crossed WSSs for reaches of hundreds of kilometers in multi-span Erbium-doped fiber amplified (EDFA) metro links supported by coherent detection.
Highlights
In recent years, we have witnessed continuous growth of bandwidth demand in the access and metropolitan area networks (MANs), as traffic remains almost confined to where it was generated.MANs must evolve toward more efficient and agile architectures which are able to address multi-Tb/s transmission and routing over variable distances and topologies, supporting any kind of services such as 5G, Mobile Edge Computing, ultra-high density TV, etc. [1]
We propose the use of directly-modulated long-wavelength vertical cavity surface emitting lasers (VCSELs) to implement sliceable bandwidth/bitrate variable transceiver (S-BVT) for capacity transmission higher than 50 Gb/s per wavelength in metropolitan area systems characterized by reduced cost, power consumption, and footprint
The most significative drawback of the direct modulation of VCSELs is frequency chirp, in particular when associated to optical filtering as in the network nodes
Summary
We have witnessed continuous growth of bandwidth demand in the access and metropolitan area networks (MANs), as traffic remains almost confined to where it was generated. Photonics 2018, 5, 51 enhanced modulation schemes or, as an alternative, coherent transmission solutions, which today are used mainly for long haul transmission, and are characterized by high cost and high-power consumption With these approaches, the expected performance enhancement in terms of throughput is limited to a factor ×2–×4, which seems to be inadequate to support 5G-and-beyond network requirements. Long-wavelength VCSEL sources are employed to realize multi-Tb/s transceivers for MAN applications; in particular, we focus the analysis on VCSEL sources emitting in the C-band, taking into account realistic optical sources and network filters. VCSELs chirp are compared; simulations of transmission employing DMT DM VCSELs and COH-D demonstrate reach distances of hundreds of kms typical of MANs. The considered OSNR are typical of MAN applications, ranging from 30 to 40 dB, which are able to support hundreds-kms-long SSMF propagations.
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