Fujikura Technical Review

In recent years, the demand for a millimeter-wave radar imaging has increased, therefore, a millimeter-wave radar with higher angular resolution has been highly expected. One of the solutions to achieve the higher angular resolution without increasing the complexity of the radar system is a sparse array radar. Generally, rain conditions are not considered in the verification of the sparse array radar performance, hence, an impact of the rain on the sparse array radar has not been clarified. For this reason, we designed and fabricated an in-house developed sparse array radar and experimentally verified the influence of the rain on the sparse array radar with several tests in a rain chamber.

Intersatellite communication requires transmitters with high data transmission capacities.
Optical communication has emerged as a promising solution to meet these requirements. To establish reliable communication links between low Earth orbit satellites and geostationary orbit satellites, transmitters with optical output power in the 10 W-class are required. Er/Yb co-doped optical fibers have been recognized as suitable candidates for achieving such high optical output power levels. Although radiation-hardened fibers for space applications are commercially
vailable, we present an improved radiation-hardened Er/Yb co-doped optical fiber and dmonstrate its capability to deliver a 10 W-class optical output.

High-power LDs, which are applied as pump sources for industrial fiber laser systems, are required to achieve not only high output and high efficiency operation but also reduced beam divergence suitable for fiber coupling, as well as improved long-term reliability. In this report, we achieved high-power and high-efficiency operation with a light output of 27.9 W and a PCE of 66.5% at a driving current of 27 A and reduced vertical divergence angles by more than 30% by optimizing the waveguide structure. Furthermore, long-term aging tests demonstrated excellent reliability even under severe operation conditions. We aim to contribute to the advancement of next-generation industrial fiber laser systems through the development of these high-performance LDs.

Millimeter-wave based technology, capable of transmitting large amounts of data in real-time with low latency and high speed, is expected to play a significant role in the fifth-generation (5G) mobile communication systems. We are developing a 28 GHz band Phased Array Antenna Module (PAAM) 「FutureAccess™」 for the 5G applications. Compared to previous PAAM, 64-element and 256-element Type-C PAAM have improved the balance between high output power and high-quality millimeter-wave signals. In this paper, we report on the performance evaluation of a 64-element PAAM and a 256-element tiled Type-C PAAM through Over-he-Air (OTA) testing.

To reduce fusion splice cost, there has been an increasing demand for indoor-outdoor (I/O) cables that combine the flame-retardant properties of inside plant (ISP) cables for indoor use and weather-resistant outside plant (OSP) cables for outdoor use. However, I/O cables in general are weaker than OSP cables, which limit the cable installation methods available. By developing Robust I/O (RIO) cables with superior mechanical strength, it has become possible to adopt the jetting installation method, which offers superior workability.

Optical connectors, which are essential components in the construction of optical networks, require cleaning prior to connection as a standard procedure to prevent degradation of communication quality caused by contamination or foreign substances. In recent years, with the growing demand for data centers, damage due to static electricity has become a critical issue in optical transceivers and related devices, electrostatic discharge protected particularly leading to performance deterioration of optical modules and failures in optical links. In response to these challenges, we have developed the "One-Click® Cleaner MPO ESD", the ESD-protective multi-fiber optical connector cleaner designed for use in electrostatic discharge protected areas (EPAs). This paper reports on the features of this product.

In the manufacturing of optical products, precision bonding technology, which mounts optical components with high positional accuracy, is an important fundamental technology. To achieve high positional accuracy, it is essential to comprehend the deformation of the adhesive joint over time during processing. Therefore, a method to analyze the displacement of optical components resulting from the deformation of a cationic polymerization UV curable adhesive was developed. First, the physical properties of the adhesive were formulated. Then equations, governing the adhesive properties, were used to perform finite element method (FEM) simulations to analyze the position of the optical component during curing of the adhesive. Experimental tests on adhesively bonded components were also conducted under conditions identical to those employed in the simulation. The results of the simulation and experiment exhibited a consistent trend, indicating the effectiveness of the modeling and simulation methods employed in this study.

This study demonstrated a transmission test assuming intra-datacenter interconnection using a 400GBASE-FR4 transceiver on a transmission system built using 2 km 4-core multicore fibers, 24 pairs of fan-out devices, and multicore fiber MPO connectors. Error-free transmission was achieved in an environment with inter-core crosstalk, and the results are reported.