Optical eigenvalue transmission based on inverse scattering transform (IST) has been studied for one of approaches to overcome the Kerr nonlinearity limit in fiber optic communications. In the recent decade, several multilevel modulation schemes that are based on IST, such as 16-ary and 64-ary signals using on-off encoding and b-modulation of multieigenvalues, have been proposed. To increase the transmission capacity and extend the transmission distance, applications of machine learning-based approaches to IST-based transmission have been proposed and demonstrated. Another prospective approach to increase the transmission capacity and extend the transmission distance in fiber optic communication involves the application of soft-decision forward error correction (SD-FEC). However, the applicability of SD-FEC to eigenvalue-modulated signals has not yet been investigated in detail because the distribution of the received signal is complicated for IST-based transmissions. In this paper, we describe in detail the theory of optical eigenvalue transmission, including the design of multilevel eigenvalue-modulated signals and the effects of noise and scaring parameters (coefficients for normalization of the nonlinear Schrödinger equation). We explain why neural network (NN) demodulators are advantageous for eigenvalue transmission systems. Consequently, we propose a combination of NN-based demodulators and SD-FEC decoding. A multilabel NN-based demodulator is employed to compute the L-value from the received eigenvalue pattern at the receiver. For a 16-ary eigenvalue-modulated signal, the proposed method outperformed a combination of the Gaussian approximation and SD-FEC in the simulation. Moreover, the experimental results show successful operation with error-free transmission through a 3000-km optical fiber line. In addition, we experimentally demonstrate the applicability of SD-FEC to a 4096-ary eigenvalue-modulated signal. The experimental results indicate that an achievable transmission distance can be extended to 1200 km using the NN demodulator and SD-FEC.

A new functional split mobile base station (MBS) has been getting attention for 5G and beyond 5G(BSG) to reduce an optical bandwidth. The MBS is split into three components: a central unit (CU), a distributed unit (DU), and a radio unit (RU). The link between a DU and a RU is connected by an optical fiber and well known as fronthaul. In particular, RUs will be densely deployed in antenna site to increase the mobile data rate. There is inefficiency in the bandwidth usage in the fronthaul link because all the RUs are not always in activated state. Therefore, a mobile operator needs a cost-effective fronthaul network. Employing the wireless multihop system has been studied to construct 5G/B5G fronthaul network. Both optical and wireless links should be employed since it is challenging to replace all of the optical link to the wireless link. However, the method of the deployment of the DU site to reduce the optical fiber cost has not been considered. This paper proposes a novel efficient deployment design of DU site incorporating wireless multihop connection in order to satisfactory reduce optical fiber deployment cost.

We analyze the throughput of fixed-length, variable-capacity (FL-VC) packet technology in OPS MANs with lengths up to several tens of kilometers. Compared to conventional OPS networks using fixed-bit-rate packets, FL-VC often offers throughput increases of ≃50% to TCP flows, and of ≃100% to UDP flows, under realistic traffic patterns. Throughput also increases with respect to equivalent topologies where switches have random-access buffers.

Mode division multiplexing (MDM) over wavelength division multiplexing (WDM) network is studied, particularly focusing on low differential mode group delay (DMGD) two-mode fiber (TMF) link in a wide spectral range. Here, the DMGD is defined as the group delay between the two guided modes, LP01and LP11modes. For the starter, We will revisit an invention of the original TMF in late 70's, followed by the DMGD-compensated TMF link and crosstalk between two mode channels due to the mode coupling effect. Next, in order to explore the feasibility of "real-time" digital signal processing (DSP) for multiple-input multiple-output (MIMO) transmission system for equalizing the mode channel crosstalk, the computational complexity of MIMO DSP will be evaluated. As a consequence, a criterion of the DMGD value to enable the realtime MIMO DSP is derived. Finally, against a backdrop of 560% predicted traffic surge of metro area network (MAN) by 2017, a deployment scenario of MDM over WDM MAN is presented as the solution, and the MDM node architecture will be discussed.

A dynamic routing and wavelength allocation technique with interplay between physical and network layer parameters encompassing four-wave mixing (FWM) awareness and the teletraffic performance of wavelength-routed optical networks has been proposed under a distributed approach. In this paper we present an online RWA encompassing FWM-induced crosstalk based upon an impairment-constraint-based routing (ICBR) called FWM-aware dynamic RWA. Our model design assumes a realistic scenario and leads to better network performance comparing to previous work approaches. A fast computational scheme in order to minimize the time of establishing a lightpath dynamically, is also evaluated, for this purpose a precomputed matrix of FWM crosstalk products is proposed and introduced into the mxFWM-aware RWA. The approach is validated through simulations showing improvement up to 30-50 percent on the provisioning time of lightpaths for different network topologies compared to a full on-line computational scheme or FWM-aware RWA.