An object is to provide an optical communication system and an optical communication method that are capable of, when assigning wavelengths on a per-service basis and providing services on a per-area basis, preventing degradation of signal quality due to linear crosstalk and preventing an increase in cost and size. An optical communication system according to the present invention includes an optical splitter 300 connecting N first ports and M second ports by a combination of 2×2 fiber optical splitters, N and M each being an integer of two or more, where wavelengths of optical signals to be received are limited for each group of optical receivers 106, by using a correlation between a fused extension length of at least one 2×2 fiber optical splitter directly connected to the first port, among the 2×2 fiber optical splitters, and wavelength output characteristics of the second port of the optical splitter 300.

An object is to provide an optical communication system capable of controlling the output ratio by port and by wavelength for incident light of different wavelengths, a method of determining the split ratio of an uneven-split optical splitter for controlling the output ratio by port and by wavelength, and a transmission range determination method for the optical communication system. The split ratio determination method for an uneven-split optical splitter according to the present invention uses the melt-draw distance to adjust the split ratio of each fiber-optic splitter included in the uneven-split optical splitter such that the light output from the farthest ONUs among each of the ports connected under the ports B to M of the uneven-split optical splitter arrives with the minimum reception sensitivity at OLT receivers in a PON system.

An object is to provide an optical communication system capable of controlling the output ratio by port and by wavelength for incident light of different wavelengths, a method of determining the split ratio of an uneven-split optical splitter for controlling the output ratio by port and by wavelength, and a transmission range determination method for the optical communication system. The split ratio determination method for an uneven-split optical splitter according to the present invention uses the melt-draw distance to adjust the split ratio of each fiber-optic splitter included in the uneven-split optical splitter such that the light output from the farthest ONUs among each of the ports connected under the ports B to M of the uneven-split optical splitter arrives with the minimum reception sensitivity at OLT receivers in a PON system.

A compounded light-focusing optical element is configured to focus light, and the compounded light-focusing optical element includes a body having a first, flat, end face and a second, curved end face, the second, curved end face being opposite to the first, flat end face, and plural optical fibers extending through the body, from the first, flat end face to the second, curved end face. The plural optical fibers are fused to each other to form the body, and end faces of the plural optical fibers, corresponding to the second, curved end face, are pointing in different directions.

An optical combiner includes: an optical fiber bundle formed by a plurality of first optical fibers; and a second optical fiber including an end surface joined to an end surface of the optical fiber bundle by fusion-splicing. The plurality of first optical fibers includes a predetermined first optical fiber and other first optical fibers. The predetermined first optical fiber is composed of one or more materials having higher softening temperatures than one or more materials of the other first optical fibers.

An optical combiner includes: an optical fiber bundle formed by a plurality of first optical fibers; and a second optical fiber including an end surface joined to an end surface of the optical fiber bundle by fusion-splicing. The plurality of first optical fibers includes a predetermined first optical fiber and other first optical fibers. The predetermined first optical fiber is composed of one or more materials having higher softening temperatures than one or more materials of the other first optical fibers.

An optical fiber sensor extends coaxially with a controllable heater to provide high-resolution axial measurement of thermal properties such as thermal convection of the surrounding, Heat removal by either conduction or convection may be used to deduce material height in a tank, or velocity of flow when coupled with localized heating, or other aspects of the material based on thermal conductivity.

An optical fiber sensor extends coaxially with a controllable heater to provide high-resolution axial measurement of thermal properties such as thermal convection of the surrounding, Heat removal by either conduction or convection may be used to deduce material height in a tank, or velocity of flow when coupled with localized heating, or other aspects of the material based on thermal conductivity.

Provided is an optical device which can control a beam quality of outgoing light. An optical device (10) includes an entrance fiber bundle (12), an exit fiber (13), and a reduced diameter part (11). The reduced diameter part (11) has (i) an entrance end surface (11a) and (ii) an exit end surface (11b) which is narrower in area than the entrance end surface (11a). In a case where the entrance end surface (11a) is viewed from a normal direction of the entrance end surface (11a), a center (C2) of the exit end surface (11b) deviates from a center (C1) of the entrance end surface (11a).

Provided is an optical device which can control a beam quality of outgoing light. An optical device (10) includes an entrance fiber bundle (12), an exit fiber (13), and a reduced diameter part (11). The reduced diameter part (11) has (i) an entrance end surface (11a) and (ii) an exit end surface (11b) which is narrower in area than the entrance end surface (11a). In a case where the entrance end surface (11a) is viewed from a normal direction of the entrance end surface (11a), a center (C2) of the exit end surface (11b) deviates from a center (C1) of the entrance end surface (11a).