US-12625329-B2 - Optical device, optical module, and optical transmission and reception apparatus

US12625329B2US 12625329 B2US12625329 B2US 12625329B2US-12625329-B2

Abstract

An optical device has a waveguide circuit, a transmitter that transmits transmitted light to the waveguide circuit, and a receiver that receives received light from the waveguide circuit. The waveguide circuit has an optical waveguide, a wavelength combiner and splitter, and a mode filter. The optical waveguide includes a first port where the transmitted light output from the transmitter is input to and a second port where the transmitted light is output from, guides the transmitted light, and guides the received light input from the second port. The wavelength combiner and splitter is arranged in the optical waveguide between the first port and the second port. The mode filter removes a higher-order mode of the received light input by use of the wavelength combiner and splitter and includes a third port that outputs the received light having the higher-order mode removed from the received light, to the receiver.

Inventors

Hirohiko Sonoda

Assignees

FUJITSU OPTICAL COMPONENTS LIMITED

Dates

Publication Date: 20260512
Application Date: 20231120
Priority Date: 20230206

Claims (8)

1 . An optical device comprising an optical waveguide circuit, an optical transmitter that transmits transmitted light to the optical waveguide circuit, and an optical receiver that receives received light from the optical waveguide circuit, wherein the optical waveguide circuit includes: an optical waveguide that includes a first port where the transmitted light output from the optical transmitter is input to and a second port where the transmitted light is output from, guides the transmitted light, and guides the received light input from the second port; a wavelength combiner and splitter arranged in the optical waveguide between the first port and the second port; and a mode filter that removes a higher-order mode of the received light input by use of the wavelength combiner and splitter and includes a third port that outputs the received light having the higher-order mode removed from the received light, to the optical receiver, wherein the mode filter is a curved waveguide having a curvature that allows the higher-order mode to be removed.
2 . The optical device according to claim 1 , wherein the optical transmitter further includes a light emitting element that emits the transmitted light that is in a single mode.
3 . The optical device according to claim 1 , wherein the mode filter has a first core and a second core that is arranged in parallel with the first core and that causes transition of the higher-order mode of the received light guided through the first core.
4 . The optical device according to claim 1 , wherein the transmitted light or the received light has a wavelength band of a cutoff wavelength of an optical fiber that is a single mode fiber (SMF) or shorter.
5 . The optical device according to claim 1 , further includes: a first optical component that optically couples between the optical transmitter and the first port; and a second optical component that optically couples between the optical receiver and the third port, wherein the first optical component includes: a first condenser lens that condenses the transmitted light from the optical transmitter; and a first optical path conversion prism that optically couples the transmitted light condensed by the first condenser lens to the first port, and the second optical component includes: a second condenser lens that condenses the received light onto the optical receiver; and a second optical path conversion prism that optically couples the received light input from the third port to the second condenser lens.
6 . The optical device according to claim 1 , further including: a first photonic wire bond that optically couples between the optical transmitter and the first port; and a second photonic wire bond that optically couples between the optical receiver and the third port.
7 . An optical module, comprising: an optical transmitter that outputs transmitted light; an optical receiver that receives received light; and an optical waveguide circuit that guides the transmitted light from the optical transmitter and guides the received light to the optical receiver, wherein the optical waveguide circuit includes: an optical waveguide that includes a first port where the transmitted light output from the optical transmitter is input to and a second port where the transmitted light is output from, guides the transmitted light, and guides the received light input from the second port; a wavelength combiner and splitter arranged in the optical waveguide between the first port and the second port; and a mode filter that removes a higher-order mode of the received light input by use of the wavelength combiner and splitter and includes a third port that outputs the received light having the higher-order mode removed from the received light, to the optical receiver, wherein the mode filter is a curved waveguide having a curvature that allows the higher-order mode to be removed.
8 . An optical transmission and reception apparatus comprising an optical transmitter that outputs transmitted light based on an electric signal according to transmitted data, an optical receiver that outputs an electric signal according to received data from received light that has been received, an optical waveguide circuit that guides the transmitted light from the optical transmitter and guides the received light to the optical receiver, and a processor that executes signal processing of the electric signals, wherein the optical waveguide circuit includes: an optical waveguide that includes a first port where the transmitted light output from the optical transmitter is input to and a second port where the transmitted light is output from, guides the transmitted light, and guides the received light input from the second port; a wavelength combiner and splitter arranged in the optical waveguide between the first port and the second port; and a mode filter that removes a higher-order mode of the received light input by use of the wavelength combiner and splitter and includes a third port that outputs the received light having the higher-order mode removed from the received light, to the optical receiver, wherein the mode filter is a curved waveguide having a curvature that allows the higher-order mode to be removed.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2023-016394, filed on Feb. 6, 2023, the entire contents of which are incorporated herein by reference. FIELD The embodiments discussed herein are related to optical devices, optical modules, and optical transmission and reception apparatuses. BACKGROUND Traffic volumes in large scale data centers are dramatically increasing with the advancement of the Internet, for example. For example, building a data-driven society is hoped for, the data-driven society utilizing artificial intelligence (AI), advancement of machine learning, the Internet of Things (IoT) connected to an enormous number of various sensors and terminals, and autonomous driving technologies. With the advancement of introduction of 5G mobile communication systems, the traffic volumes are increasing acceleratingly. For 5G, for example, about 100 antenna base stations are needed in a cell having a radius of two kilometers. For 6G, higher radio frequencies and smaller cell radii are expected, and for example, about 10,000 antenna base stations are thus needed in a 6G cell having a radius of two kilometers. For 6G, communication of one terabit per second (Tbps) or faster, which is even faster than 100 gigabits per second (Gbps), is expected. Conventional 3G and 4G base stations are installed in or near buildings of communication service providers and these base stations are connected to networks. For 5G and 6G base stations, more of so-called optical fronthaul is also being introduced. This so-called optical fronthaul has optical fibers extending from a 3G or 4G base station or an office of a communication service provider, the office having a base station installed therein. Therefore, there is a demand for development of an optical transceiver having a single-fiber bidirectional optical device installed therein, in years to come, for example, by 2030, the single-fiber bidirectional optical device using a single mode fiber for a distance less than ten kilometers and being 100 Gpbs-class. FIG. 9 is a diagram illustrating an example of an optical device 100. The optical device 100 illustrated in FIG. 9 is a single-fiber bidirectional optical device. The optical device 100 has an optical transmission terminal portion 110, an optical receiving terminal portion 120, a device body 130, and an optical fiber connecting portion 140. The optical transmission terminal portion 110 has a light emitting element 111 and a condenser lens 112. The light emitting element 111 is a laser diode (LD) that emits transmitted light. The condenser lens 112 is a lens that condenses the transmitted light from the light emitting element 111. The optical receiving terminal portion 120 has a condenser lens 121, a preamplifier 122, and a light receiving element 123. The condenser lens 121 is a lens that condenses received light. The preamplifier 122 is an optical amplifier that optically amplifies the received light condensed by the condenser lens 121. The light receiving element 123 is a photodiode (PD) that implements electric conversion of the received light that has been optically amplified by the preamplifier 122. The device body 130 has an optical waveguide 131 and a wavelength filter 132. The optical waveguide 131 is a waveguide where the transmitted light and the received light are guided through. The optical waveguide 131 has an optical input port 131A optically coupled to the optical transmission terminal portion 110, an optical output port 131B optically coupled to the optical receiving terminal portion 120, and a transmission line port 131C optically coupled to the optical fiber connecting portion 140. The optical fiber connecting portion 140 is a connecting portion connected to an optical fiber 200. The wavelength filter 132 is arranged in the optical waveguide 131, transmits the transmitted light from the optical input port 131A therethrough, outputs the transmitted light that has been transmitted therethrough, to the transmission line port 131C, and reflects the received light from the transmission line port 131C to the optical output port 131B. However, a higher-order mode is generated in the optical device 100 by influence of, for example, reflection in the transmission line on the received light in the fundamental mode guided through the optical fiber 200. Therefore, a function of removing the higher-order mode is needed for the optical device 100 to be adapted, in particular, to long distance transmission and high bit rate transmission. In a known method, a mode filter to remove the higher-order mode is thus arranged on the transmission line of the optical fiber 200. FIG. 10 is a diagram illustrating an example of a configuration having the optical device 100 and a mode filter 300 connected to each other. A system configuration illustrated in FIG. 10 includes the optical device 100, the mode filter 300, a first op