Improved Performance Robustness of DSP-Enabled Flexible ROADMs Free from Optical Filters and O-E-O Conversions

Abstract

Utilizing Hilbert-pair-based digital filtering, intensity modulation and passive optical coupling, DSP-enabled flexible ROADMs are reported, which are free from both optical filters and O-E-O conversions and also offer excellent flexibility, colorlessness, gridlessness, contentionlessness, adaptability and transparency to physical-layer network characteristics. In this paper, the ROADM performance robustness against variations in numerous network design aspects is, for the first time, extensively explored in IMDD-based optical network nodes. Numerical results show that DSPs not only enable the ROADMs to dynamically and flexibly perform add/drop operations at wavelength, subwavelength and spectrally overlapped orthogonal sub-bands levels, but also considerably improve the ROADM performance robustness against variations in modulation formats, transmission system characteristics/impairments, as well as terminal equipment configurations. Index Terms-Digital filtering, digital signal processing (DSP), intensity modulation, reconfigurable optical add/drop multiplexer (ROADM), performance robustness.

Real-time experimental demonstration of DSP-enabled soft-ROADMs with multi-level flexible add/drop functions for cloud access networks

“…Furthermore, as the contentionless feature is controlled by the SDN control plane, it is thus feasible to implement soft-ROADMs with colorless, directionless and contentionless (CDC) functionality. To dynamically configure the required network interconnectivity, a centralized SDN controller communicates, via a protocol such as extended OpenFlow, with embedded DSP controllers in the soft-ROADMs and the TETs using an approach presented in [13][14]. The required signaling channel could be implemented as an optical supervisory channel (OSC) carried by a dedicated wavelength outside the WDM wavelength band, as is the case in conventional ROADM technologies.…”

“…To address such an unprecedented technical challenge, we have recently proposed lowcost digital signal processing (DSP)-enabled optical-domain ROADMs, termed here soft-ROADMs [12][13][14]. The proposed soft-ROADM operations are independent of the underlying signal and channel characteristics, so the soft-ROADMs are highly versatile in their applications in CANs.…”

“…The proposed soft-ROADM operations are independent of the underlying signal and channel characteristics, so the soft-ROADMs are highly versatile in their applications in CANs. The soft-ROADMs have very simple architectures comprising of passive optical coupler-based add elements and intensity modulation (IM)-based drop elements without incorporating either costly narrowband optical tunable band pass-filters (OTBPFs) or opticalelectrical-optical (O-E-O) signal conversions [12][13][14]. Enabled by DSP, the soft-ROADM provides SDN-controllable, dynamic and flexible optical switching at wavelength, subwavelength and spectrally-overlapped orthogonal sub-band levels, in intensity modulation and direct detection (IMDD)-based networks incorporating embedded Hilbert-pair-based digital orthogonal filters in terminal equipment transceivers (TETs), whilst still maintaining excellent transparency to various network features.…”

“…Enabled by DSP, the soft-ROADM provides SDN-controllable, dynamic and flexible optical switching at wavelength, subwavelength and spectrally-overlapped orthogonal sub-band levels, in intensity modulation and direct detection (IMDD)-based networks incorporating embedded Hilbert-pair-based digital orthogonal filters in terminal equipment transceivers (TETs), whilst still maintaining excellent transparency to various network features. The performance of the soft-ROADM has been comprehensively investigated using numerical simulations [12][13][14] and its drop operation has also been experimentally demonstrated using an off-line DSP receiver [15]. More recently the basic technical feasibility of both the add and drop functions at sub-band level have been demonstrated in an experimental system employing a real-time soft-ROADM [16].…”

Impact Study and Evaluation of Higher Modulation Schemes on Physical Layer of Upcoming Wireless Mobile Networks

“…To accommodate the developed schemes of modulation format in the physical layer (PHY) of wireless mobile networks, the current waveform Orthogonal Frequency Division Multiplexing (OFDM) is utilized due to its high resistance against the Inter-Symbol Interference (ISI), better BW efficiency, and improved bit rate of transmission [9]. Thus, the newly examined formats of modulation (128 QAM & 256 QAM) are explored employing the most popular transmission air interface OFDM.…”