A Zadoff–Chu (ZC) sequence-based low-complexity hitless upstream time synchronization scheme is proposed for an orthogonal frequency division multiple access passive optical network configured cloud radio access network fronthaul. The algorithm is based on gradual loading of the ZC sequences, where the phase discontinuity due to the cyclic prefix is alleviated by a frequency domain phase precoder, eliminating the requirements of guard bands to mitigate intersymbol interference and inter-carrier interference. Simulation results for uncontrolled-wavelength asynchronous transmissions from four concurrent transmitting optical network units are presented to demonstrate the effectiveness of the proposed scheme.
Alamouti space-time coding is modified in the form of polarization-time coding to combat against polarization mode dispersion (PMD) impairments in exploiting a polarization diversity multiplex (PDM) gain with simple intensity modulation and direct detection (IM/DD) in optical transmission systems. A theoretical model for the proposed IM/DD Alamouti polarization-time coding (APTC-IM/DD) using nonreturn-to-zero on-off keying signal can surprisingly eliminate the requirement of channel estimation for decoding in the low PMD regime, when a two-transmitter and two-receiver channel is adopted. Even in the high PMD regime, the proposed APTC-IM/DD still reveals coding gain demonstrating the robustness of APTC-IM/DD. In addition, this scheme can eliminate the requirements for a polarization state controller, a coherent receiver, and a high-speed analog-to-digital converter at a receiver. Simulation results reveal that the proposed APTC scheme is able to reduce the optical signal-to-noise ratio requirement by ∼3 dB and significantly enhance the PMD tolerance of a PDM-based IM/DD system.
Physical layer of high-end network system uses multiple interface arrays. Under the load-balancing perspective, light
load can be distributed to multiple interfaces. However, it can cause energy inefficiency in terms of the number of poor
utilization interfaces. To tackle this energy inefficiency, traffic off-balancing algorithm for traffic adaptive interface
sleep/awake is investigated. As a reference model, 40G/100G Ethernet is investigated. We report that suggested
algorithm can achieve energy efficiency while satisfying traffic transmission requirement.
All-optical OFDM data transmission opens up a new realm of advanced optical transmission at extreme data rates, as
subcarriers are multiplexed and demultiplexed by all optical discrete Fourier transforms (DFT). This paper reviews the
principles of all optical OFDM transmission and its system application techniques, providing the generic ideas and the
practical implementation issues to achieve 100Gbps or higher data rates with a spectral efficiency of 1 bps/Hz or better.
This paper also include discussions on all-optical OFDM implementation variants such as an AWG-based OFDM
multiplexer and demultiplexer, a receiver design without optical sampling, a transmitter design with frequency-locked
cw lasers, an OFDM cyclic prefix designs, and a chromatic dispersion mitigation technique.
Ethernet ring protection (ERP) is a new technology based on OAM (operations, administration, and maintenance) being
standardized by the ITU-T G.8032 working group. In this paper, we present the recent development of Ethernet ring
protection which is called FDB (filtering database) flush scheme and propose a new Ethernet ring protection technique
introducing a managed FDB using APS to deliver information how to fix FDB selectively. We discuss the current
development of the ERP technology at ITU-T and performance comparisons between different proposals.
The Ethernet technoglogy rapidly gains importance as becoming a dominant solution for a converged transport network. Recently added features such as QoS handling and OAM functions in the framework of ITU-T NGN provides a means for performance improvement to meet carrier-class network requirements. In addition, integration with newly developed T-MPLS by ITU-T offers a potential to replace current SDH/SONET-based network infrasctructure.
We propose a cost effective optical packet switching system using shared wavelength converter pool. We also present its cost model and show the overall system cost for the target performance. The benefits of the proposed system is compared with the conventional approaches in terms of blocking performance and overall system cost.
Fully reconfigurable broadcast and select OADMs are compared to conventional designs for ULH networks. The feasibility of an 80 x10.7 Gb/s broadcast and select OADM chain with an unregenerated reach exceeding 4160 km is demonstrated. Key engineering issues for widespread commercial deployment of all-optical ULH networks include ASE noise accumulation, filter concatenation effects, dispersion, fiber non-linearity, and crosstalk impairments.
Advanced optical fibers enable high-capacity transmission for long reach systems and help to retain margin for networking. To do this they must support broadband operation, reduce nonlinear impairments, enable distributed gain and simplify networking. Here we describe fibers that incorporate dispersion management to extend span length and system reach over a broad bandwidth by compensating dispersion slope, reducing nonlinear impairments, and optimizing noise figure.
By use of novel technologies for broadcast and select (B&S) node architecture and a dispersion-managed fiber system, we demonstrate an ultra-long-haul (ULH) network system consisting of 13 optical add/drop multiplexers (OADM) in an optically transparent 4160-km network chain. All 80 channels at a bit rate of 10.7-Gbps, spaced with a 50-GHz wavelength grid, perform >13.6 dBQ, which offer a 2-dBQ optical margin when forward error correction is applied. A dynamic spectral equalizer with 40 dB extinction ratio is used for the B&S OADM, which offers simultaneous blocking and leveling functions for channel drop and power equalization. The cross-talk penalty requirement of an OADM in the ULH system is studied.
In this paper, we propose a single-hop TDMA optical network with throughput of several Tb/s. This high throughput is achieved by combining spectrum encoding and fast demultiplexing. Fast packet switching is accomplished by using a rapidly tunable delay line. The frequency domain DPSK modulation is adopted, which provides 3 dB improvement over FD-OOK. Finally, we discuss a scalable protocol that can be employed in a network with a large number of channels and users.
Embedding of end-tapered, thin-cladding fiber bundles for board- level large bandwidth optical clock distribution is proposed and implemented. Fan-outs of 1 to 64- and 128-nodes on a printed circuit board of area 13 X 9 cm2 are experimentally demonstrated. Dispersion measurement shows a 30 picosecond pulse broadening over 30 cm length of the fiber, thereby indicating multi Gb/s clock delivery capability. Power coupling efficiency of 3 dB with coupling nonuniformity of 4.7 - 5.5 dB is observed.
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