It is used to connect optical fiber or optical fiber butt pigtail, which is equivalent to making a joint (fiber butt pigtail refers to the butt joint of the fiber core of the optical fiber and the pigtail instead of the pigtail head mentioned in the former), and is used for. It is used to connect optical fiber or optical fiber butt pigtail, which is equivalent to making a joint (fiber butt pigtail refers to the butt joint of the fiber core of the optical fiber and the pigtail instead of the pigtail head mentioned in the former), and is used for. School of Physics and Microelectronics, Zhengzhou University, Zhengzhou 450052, China Department of Electrical and Electronic Engineering, College of Engineering, Southern University of Science and Technology, Shenzhen 518055, China Author to whom correspondence should be addressed. The rapid. There, one has to numerically calculate the back-reflection, e. It is interesting to consider some more details. For example, does it matter for the losses from which fiber the input light comes, if the mode sizes are. Fiber optics technology has revolutionized communication systems with its high-speed data transmission capabilities. A critical aspect of fiber optics is the joining of optical fibers, ensuring efficient light transfer from one fiber to another. There are many different types of FORJs. Examples include a single-channel FORJ, multi-channel FORJ and hybrid FORJ. This paper is based on our invited talk(2) in a symposium on SDM held at the annual meeting of the Laser Society of Japan (Jan 24-Jan 26, 2018) and provides further information describing MCF-specific design parameters and the efforts made for MCF R&D at Sumitomo Electric Industries, Ltd.