The rise of next-generation logistics systems featuring autonomous vehicles and drones has brought to light the severe problem of Global navigation satellite system (GNSS) location data spoofing. While signal-based anti-spoofing techniques have been studied, they can be challenging to apply to current commercial GNSS modules in many cases. In this study, we explore using multiple sensing devices and machine learning techniques such as decision tree classifiers and Long short-term memory (LSTM) networks for detecting GNSS location data spoofing. We acquire sensing data from six trajectories and generate spoofing data based on the Software-defined radio (SDR) behavior for evaluation. We define multiple features using GNSS, beacons, and Inertial measurement unit (IMU) data and develop models to detect spoofing. Our experimental results indicate that LSTM networks using ten-sequential past data exhibit higher performance, with the accuracy F1 scores above 0.92 using appropriate features including beacons and generalization ability for untrained test data. Additionally, our results suggest that distance from beacons is a valuable metric for detecting GNSS spoofing and demonstrate the potential for beacon installation along future drone highways.

Remote control scheme for the ROADMs (Reconfigurable Optical Add/Drop Multilplexers) were designed, and 3 sets of the ROADM were manufactured for use in IP-over-CWDM networks. The control performance was examined, and lightpaths could be reconfigured successfully by the control.

A novel fiber jacket removing system by a CO2 laser has been proposed to realize compact packaging of optical components. It has been clarified experimentally that excess-fiber-free MT connectorization is possible for 4-fiber ribbon.

Friction coefficient between coated optical fibers and a loose-tube was evaluated theoretically and experimentally. Simple method was investigated for direct measurement of frictional force and the measured coefficient by the method has been found to represent frictional characteristics of a long stranded optical cable excellently.

A bit-error-free optical signal switching method from one to another fiber has been proposed for high-bit-rate optical transmission lines. The intensity modulated signal powers of 1.8 Gbit/s, which had been divided by an acousto-optic deflector and propagated through the 2 fibers, were recombined without bit-errors. Optical signals were switched successfully between 25 km long fibers without degradation of bit-error-rate performance.

A novel optical signal splitting method using a holographic transmission grating is proposed for optical communication use. An input beam from a SM-fiber is variably split into two output SM-fibers. Its applicability to the bit-error-free switching of a 1.8 Gbit/s signal is successfully demonstrated.

A new method for evaluating optical fiber strain in a bent cable is proposed. The method is applied to fiber strain measurement in an actual optical cable and is found to be effective.

Optimum conditions of the laser power P and the scan speed V were investigated experimentally so as to burn and remove the jacket of a 4-fiber ribbon completely by a system with a CO2 laser. It has been clarified that the optimum region can be given by 3 lines, which represent 2 lower limits of the laser power, depending on the scan speed, and an upper limit of the laser power to avoid soot from remaining on the fibers at high laser power region. The optimum conditions enable us to remove the jacket effectively by the system to provide excess-fiber-free compact packaging of optical components.

Reducing the time complexity of character matching is critical to the development of efficient Japanese Optical Character Recognition (OCR) systems. To shorten the processing time, recognition is usually split into separate pre-classification and precise recognition stages. For high overall recognition performance, the pre-classification stage must both have very high classification accuracy and return only a small number of putative character categories for further processing. Furthermore, for any practical system, the speed of the pre-classification stage is also critical. The associative matching (AM) method has often been used for fast pre-classification because of its use of a hash table and reliance on just logical bit operations to select categories, both of which make it highly efficient. However, a certain level of redundancy exists in the hash table because it is constructed using only the minimum and maximum values of the data on each axis and therefore does not take account of the distribution of the data. We propose a novel method based on the AM method that satisfies the performance criteria described above but in a fraction of the time by modifying the hash table to reduce the range of each category of training characters. Furthermore, we show that our approach outperforms pre-classification by VQ clustering, ANN, LSH and AM in terms of classification accuracy, reducing the number of candidate categories and total processing time across an evaluation test set comprising 116,528 Japanese character images.

Tensile strength of heavy metal fluoride glass fibers was investigated. The effect of proof testing on the fiber strength was evaluated theoretically and experimentally. It was found that the strength distribution of the fluoride fiber after proof testing can be predicted, based on the slow-crack growth model. This result enables to extend the cable design for silica fibers to that for fluoride fibers to assure long-term reliability.

A high-density cable structure, containing fiber ribbons inserted tightly into slots, is proposed for a high-fiber-count feeder line. This paper describes theoretical and experimental investigations on the residual strain due to inserting ribbons into a helical slot in this cable. The residual strain caused by different insertion methods is clarified and a strain suppression method is discussed. Based on the results, 600-fiber cable is manufactured and the transmission and mechanical performances are confirmed to be excellent.

A stackable reconfigurable optical add/drop multilplexer has been proposed to give wavelength transparency to IP-over-CWDM networks. It was clarified by experiments that the proposed structure was wavelength transparent.

A bidirectional amplification module has been proposed for use in IP-over-CWDM networks. The module is based on a bidirectional erbium-doped fiber amplifier. The loss compensation characteristics of the module obtained in a bidirectional IP transmission experiment confirmed that the losses of the optical node and the transmission fiber in the network can be compensated for effectively by the module making it possible to increase the number of nodes and the total fiber length of the network.

A new optical fan-out adapter is proposed and fabricated by applying the jacket removing system with a CO2 laser. The fan-out adapter has both the multi-fiber connection function and the fiber separating function for single-fiber connections. In order to remove the jacket of a fiber ribbon to connectorize and fabricate the fan-out adapter, the optimum conditions of the laser power P and the scan speed V are clarified for the jacket removing. Based on the optimum conditions, the fan-out adapter was fabricated successfully. Individual fibers could be taken out from the MT connector of the fan-out adapter. The connection losses of the fabricated fan-out adapter were comparable with the values of commercially available MT connectors and SC connectors. The length of the fabricated fan-out adapter was 27 mm, including 2 MT connectors. This result clarifies that the size of the connection with a fan-out can be reduced dramatically by the proposed fan-out adapter.