Optical Supervisory Channel Research Articles

Mitigating nonlinear penalty induced from a low-speed optical supervisory channel on coherent signals.

With the increasing signal rates of a long-haul backbone dense-wavelength-division-multiplexing (DWDM) transmission system, e.g., from 100 Gb/s to 400 Gb/s and even to 800 Gb/s, optical path impairments simultaneously become more severe. Harmful factors being formerly insignificant become noticeable, e.g., nonlinear phase noise (NPN) on main DWDM channels induced by the cross-phase modulation (XPM) from the low-speed optical supervisory channel (OSC). Field trials show that a greater than 5.13-dB penalty can be observed on the shortest channel of 400G DP-16QAM-PCS over G.654.E links, which greatly degrades the overall transmission performance and limits the maximum reach. In this paper, we propose a dual-OSC structure with opposite signals to compensate for performance degradation caused by OSC-induced NPN. This method involves no extra digital signal processing (DSP), which is not only simple but also applicable for universal signal rates. By experimental demonstration, a 1.32-dB gain in Q (dB) for 200G DP-16QAM transmission over 1618-km G.652.D can be done, almost achieving the same performance as the no OSC case.

Penalty mitigation for OSC-induced XPM in long-haul WDM coherent systems by digital up-conversion coding.

Due to the cross phase modulation (XPM) effect, in long-haul high-speed dense wavelength division multiplexing (DWDM) coherent systems, using a low-speed on-off-keying (OOK) format optical supervisory channel (OSC) will introduce extra nonlinear phase noise, which restricts the transmission distance. In this paper, we propose a simple OSC coding method to mitigate the OSC-induced nonlinear phase noise. According to the split-step solution of the Manakov equation, we up-convert the baseband of the OSC signal out of the pass-band of the walk-off term to reduce the spectrum density of XPM phase noise. Experimental results show that the optical signal to noise ratio (OSNR) budget on the 400 G channel of 1280-km transmission is improved by 0.96 dB, which achieves almost the same performance with the no OSC case.

Optical Layer Impairments and Their Mitigation in C+L+S+E+O Multi-Band Optical Networks With G.652 and Loss-Minimized G.654 Fibers

The combination of multi-band optical transmission and ITU-T G.654 loss-minimized large-effective-area fibers enables superior network performance in the low-loss C+L wavelength bands. As the maximum cut-off wavelength of the G.654 fiber is increased to 1530 nm, from 1260 nm in the commonly used G.652 fiber, the multi-path interference (MPI) resulting from the interplay between the fundamental LP01 mode and the high-order LP11 mode needs to be considered when expanding the multi-band transmission window to cover the S+E+O bands. In this paper, we study optical layer impairments such as the LP01-LP11 mode coupling induced MPI in G.654 fiber, the negative impact of the stimulated Raman scattering (SRS) on the use of optical supervisory channel (OSC) and optical time domain reflectometer (OTDR) in all fiber types, and the four-wave-mixing (FWM) issue in the O-band transmission over G.652 fiber, and discuss the corresponding mitigation techniques. Extensive measurements of G.654.E fibers are made to evaluate the MPI. For impact of MPI, we include it, along with the nonlinear interference, in the generalized Gaussian noise model to accurately assess the link performance, and mitigation strategies are discussed. Additional considerations of diverse optical link conditions on amplification schemes, link distances, and cost constraints are made for provisioning C+L+S+E+O multi-band optical networks with the combined use of both G.652 and G.654 fibers, aiming for the optimal utilization of the multi-band transmission in future ultrahigh-capacity optical networks for a wide variety of applications.

Time transfer through the optical supervisory channel in wavelength division multiplexing systems.

We present an optical fiber time transfer scheme through the optical supervisory channel (OSC) in wavelength division multiplexing (WDM) systems. A sub-band of the standard OSC band is used to transmit time signals by only adding sub-OSC filters in commercial WDM systems. The transmission of the existing communication data service is not affected. The wavelengths of bidirectional time transmission in the same sub-band can be very close, or even the same, to maximize the bidirectional propagation symmetry and improve the precision of time transfer. Combined time, optical supervisory signal, and communication data transmission is experimentally demonstrated along a single 100km optical fiber in a WDM system in laboratory.

Experimental Demonstration of Disaggregated Emergency Optical System for Quick Disaster Recovery

Disaggregation and white-box approaches are useful in expediting disaster recovery of optical transport networks. When an optical network system is damaged by a large disaster, the damaged devices can be replaced by the disaggregated functional devices, while disregarding vendor boundaries. In the light of the disaggregation and white-box approaches, we are developing a prototype of disaggregated portable emergency optical system (EOS) for early and low-cost postdisaster recovery. The EOS is customizable, and different functions can be selected to meet the different requirements in disaster recovery. In addition to replacing the damaged functions of the original optical system with an EOS, we introduce two new disaggregated functions into the EOS for postdisaster recovery. First, we introduce an optical supervisory channel handshake scheme to aid the interconnection of the surviving optical resources. Second, we introduce a scheme to achieve the quick recovery of the damaged control plane with the surviving or first restored wireless access capability. This is highly desired not only for emergency network control, but also for the quick collection of the network damage information. These two new functions have been implemented into the EOS prototype. We experimentally demonstrated the network recovery of the data-plane and the control-plane with the EOS.

Measurements and modeling of multipath interference at wavelengths below cable cut-off in a G.654 optical fiber span.

Transmission below the cable cut-off wavelength may be a concern in some systems, especially for an optical supervisory channel (OSC) operating below the signal transmission band in systems built with G.654 fiber. In this work, we constructed a cabled span of G.654-compliant fiber and measured the multipath interference (MPI) generated during propagation through the span at a range of wavelengths below the cable cut-offs of the constituent fibers. Measurements were made under a range of conditions including different splice losses and the presence or absence of higher order mode filters placed around the splices. MPI levels were found to be sufficiently low at wavelengths far below the average cable cut-off such that OSC transmission was penalty-free. We compare the experimental results to modeling predictions and find very good agreement.

Software defined elastic optical networking in temporal, spectral, and spatial domains

This paper discusses architecture, protocol, technologies, systems, and networking testbed for software-defined elastic optical networking in temporal, spectral, and spatial domains. By exploiting the progress in elastic optical networking (EON) in temporal and spectral domains utilizing dynamic optical arbitrary waveform generation and measurement technologies, and by extending the EON concept into the spatial domain through the new orbital angular momentum-based spatial division multiplexing, we realize EON exploiting elasticity in temporal, spectral, and spatial domains (3D-EON). Routing, spectral, spatial mode, and modulation format assignment with fragmentation awareness as well as hitless defragmentation for high capacity, high quality of service, and resource-efficient networking will be pursued. OpenFlow-based 3D-EON testbed at UC Davis includes optical supervisory channel with optical performance monitoring for software-defined networking with an adaptive observe-analyze-act cycle.

Stimulated Brillouin scattering suppression using cross-phase modulation induced by an optical supervisory channel in WDM links

A stimulated Brillouin scattering (SBS) suppression method is proposed for wavelength-division-multiplexed (WDM) links, based on the cross-phase modulation (XPM) effect induced by an optical supervisory (SV) channel. Since the XPM on each signal channel is induced by the 52-Mb/s optical SV channel, the SBS suppression is nearly insensitive to WDM signal channels. We experimentally demonstrate that the proposed method can increase the SBS threshold and reduce the error floors irrespective of the bit rate, channel power, channel wavelength, and channel spacing of the WDM channels.

All-optical four-fiber bidirectional line-switched ring

An all-optical four-fiber bidirectional line-switched ring (O-4F/BLSR) architecture is proposed. This new physical layer networking protocol uses wavelengths as tributaries and an optical supervisory channel to carry overhead information. Optical channels can be added and dropped from the ring, and virtual wavelength paths can be provisioned. Both node and link failures of a network can be protected through a two layer protection scheme. Protection switching within the optical multiplex section layer (OMS) restores failure caused by loss of optical continuity in a way similar to the SONET 4F/BLSR line switching. Protection switching within the optical channel layer restores single channel failure using 1:N protection. Test results show that the O-4F/BLSR can restore traffic in less than 50 ms. A self-healing, bandwidth efficient, and scalable all-optical transport network evolving from this O-4F/BLSR architecture is possible.