This paper presents an application of low-coherence interferometry for measurement of mode field diameters (MFDs) of a few-mode fiber and shows its performance compared with another method using a mode multiplexer. We found that the presented method could measure MFDs in a few-mode fiber even without any special mode multiplexers.

To accelerate research on Beyond 5G (B5G) technologies in Japan, we propose an algorithm that designs mesh-type metropolitan area network (MAN) models based on a priori Japanese regional railway information, because ground-truth communication network information is unavailable. Instead, we use the information of regional railways, which is expected to express the necessary geometric structure of our metropolitan cities while remaining strongly correlated with their population densities and demographic variations. We provide an additional compression algorithm for use in reducing a small-scale network model from the original MAN model designed using the proposed algorithm. Two Tokyo MAN models are created, and we provide day and night variants for each while highlighting the number of passengers alighting/boarding at each station and the respective population densities. The validity of the proposed algorithm is verified through comparisons with the Japan Photonic Network model and another model designed using the communication network information, which is not ground-truth. Comparison results show that our proposed algorithm is effective for designing MAN models and that our result provides a valid Tokyo MAN model.

Past disasters, e.g., mega-quakes, tsunamis, have taught us that it is difficult to fully repair heavily damaged network systems in a short time. The only method for quickly restoring core communications is to start by fully utilizing the surviving network resources from different networks. However, as these networks might be built using different vendors' products (which are often incompatible with each other), the interconnection and utilization of these surviving resources are not straightforward. In this paper, we consider an all-optical multi-vendor interconnection method as an efficient reactive approach during disaster recovery. First, we introduce a disaster recovery scenario in which we use the multi-vendor interconnection approach. Second, we present two sub-problems and propose solutions: (1) network planning problem for multi-vendor interconnection-based emergency optical network construction and (2) interconnection problem for multi-vendor optical networks including both the data-plane and the control-and-management-plane. To enable the operation of multi-vendor systems, command translation middleware is developed for individual vendor-specific network control-and-management systems. Simulations are conducted to evaluate our proposal for sub-problem (1). The results reveal that multi-vendor interconnection can lead to minimum-cost network recovery. Additionally, an emergency optical network prototype is implemented on a two-vendor optical network test-bed to address sub-problem (2). Demonstrations of both the data-plane and the control-and-management-plane validate the feasibility of the multi-vendor interconnection approach in disaster recovery.

A translucent wavelength switched optical network (WSON) is a cost-efficient infrastructure between opaque networks and transparent optical networks, which aims at seeking a graceful balance between network cost and service provisioning performance. In this paper, we experimentally present a resilient translucent WSON with the control of an enhanced path computation element (PCE) and extended generalized multi-protocol label switching (GMPLS) controllers. An adaptive routing and wavelength assignment scheme with the consideration of accumulated physical impairments, wavelength availabilities and regenerator allocation is experimentally demonstrated and evaluated for dynamic provisioning of lightpaths. By using two different network scenarios, we experimentally verify the feasibility of the proposed solutions in support of translucent WSON, and quantitatively evaluate the path computation latency, network blocking probability and service disruption time during end-to-end lightpath restoration. We also deeply analyze the experimental results and discuss the synchronization between the PCE and the network status. To the best of our knowledge, the most significant progress and contribution of this paper is that, for the first time, all the proposed methodologies in support of PCE/GMPLS controlled translucent WSON, including protocol extensions and related algorithms, are implemented in a network testbed and experimentally evaluated in detail, which allows verifying their feasibility and effectiveness when being potentially deployed into real translucent WSON.

Large-scale disasters can lead to a severe damage or destruction of optical transport networks including the data-plane (D-plane) and control and management-plane (C/M-plane). In addition to D-plane recovery, quick recovery of the C/M-plane network in modern software-defined networking (SDN)-based fiber optical networks is essential not only for emergency control of surviving optical network resources, but also for quick collection of information related to network damage/survivability to enable the optimal recovery plan to be decided as early as possible. With the advent of the Internet of Things (IoT) technologies, low energy consumption, and low-cost IoT devices have been more common. Corresponding long-distance networking technologies such as low-power wide-area (LPWA) and LPWA-based mesh (LPWA-mesh) networks promise wide coverage sensing and environment data collection capabilities. We are motivated to take an infrastructure-less IoT approach to provide long-distance, low-power and inexpensive wireless connectivity and create an emergency C/M-plane network for early disaster recovery. In this paper, we investigate the feasibility of fiber networks C/M-plane recovery using an IoT-based extremely narrow-band, and lossy links system (FRENLL). For the first time, we demonstrate a field-trial experiment of a long-latency/loss tolerable SDN C/M-plane that can take advantage of widely available IoT resources and easy-to-create wireless mesh networks to enable the timely recovery of the C/M-plane after disaster.

This paper presents a comparative study of the number of pieces of optical transport equipment, network cost and power consumption depending on the transmission reach of the 400-Gb/s-based signal between flexible-bitrate networks using 100-Gb/s and 400-Gb/s signals and 100-Gb/s-based single-line-rate networks. In this study, we use three types of network topologies: a North American network topology, a European network topology and a Japan photonic network topology. As for the transmission reach of the 400-Gb/s-based signal, considering performance margins, different transmission reaches of the 400-Gb/s signal are assumed varying from 300km to 600km with 100-km increments. We show that the 100-Gb/s and 400-Gb/s-based flexible-bitrate networks are effective for cutting the total number of pieces of equipment and could be effective for reducing network cost and power consumption depending on the transmission reach of the 400-Gb/s signal in the case of a relatively small-scale network.

Software defined networking (SDN) and OpenFlow, which enables the abstraction of vendor/technology-specific attributes, improve the control and management flexibility of optical transport networks. In this paper, we present an interoperability demonstration of SDN/OpenFlow-based optical path control for multi-domain/multi-technology optical transport networks. We also summarize the abstraction approaches proposed for multi-technology network integration at SDN controllers.