Optical device

Abstract

The present disclosure provides an optical device in which an optical transmitter including a plurality of optical modulators and an optical receiver including a plurality of photodetectors are integrated on a chip substrate, the transmitter and the receiver being arranged in series in the optical axis direction of the optical modulators. This configuration eliminates the space formed on the side of the optical receiver where optical circuit elements are not mounted, resulting in a smaller chip size and improved mounting efficiency of the optical device.

Description

Optical Devices

[0001] The present invention relates to an optical device, and more particularly to an optical device having an optical transmitter including a plurality of optical modulators and an optical receiver including a plurality of photodetectors.

[0002] Ethernet (registered trademark), a connection standard using optical fiber, specifies the transmission method for a transmission speed of 100 Gb / s and a transmission distance of 500 m as follows: The baud rate is 26.5 Gbaud, the modulation method is NRZ (Non Return Zero), and optical signals are transmitted using four parallel SMFs (Single Mode Fibers). Meanwhile, the 800 Gb / s Ethernet standard currently being formulated by the IEEE for a transmission distance of 500 m specifies a baud rate of 53 Gbaud, the modulation method is PAM4 (Pulse Amplitude Modulation 4), and optical signals are transmitted using eight parallel SMFs. Thus, optical transceivers are becoming faster, i.e., using higher baud rates and multilevel coding, and their capacity is increasing, i.e., the number of parallel connections is increasing.

[0003] Figure 1 shows the configuration of a conventional optical transceiver. This is an example of an optical transceiver 10 that transmits and receives optical signals using four parallel SMFs (see, for example, Non-Patent Document 1). On the transmitting side, continuous wave (CW) light output from a laser diode (LD) 13 is modulated in an optical modulator in an optical transmitter (TX) 14 using an electrical signal supplied via a driver circuit 12 from a DSP chip 11 that processes signals. The transmitted optical signal is then supplied to a connector 15 connected to the SMF. On the receiving side, the received optical signal from the SMF is received by an optical receiver (RX) 16, converted into an electrical signal, amplified by an amplifier (TIA) 17, and supplied to the DSP chip 11. In the conventional optical transceiver 10, the TX 14 and RX 16, which are optical devices in the optical system, are integrated into a photonic integrated circuit (PIC) 20 called a PE (Photonic Engine).

[0004] FIG. 2 shows the configuration of a PIC in a conventional optical transceiver. This is an example of an optical transceiver 10 that transmits and receives optical signals using four parallel SMFs. Only the main components of the optical components constituting the optical transmitter 14 and optical receiver 16 in the PIC 20 are illustrated. The optical transmitter 14 in the PIC 20 has four optical modulators (Mod) 21a-21d arranged in parallel. Continuous wave (CW) light output from the LD 13 is branched into four paths and supplied to the four Mods 21a-21d. The CW light is modulated by an electrical signal supplied from the driver circuit 12 and output as a transmitted optical signal. Meanwhile, the optical receiver 16 has four photodetectors (PD) 22a-22d arranged in parallel. The received optical signal from the SMF is photoelectrically converted by the PD 22 (hereinafter, the sub-numbers of the reference numerals in the drawings will be omitted as appropriate).

[0005] As shown in FIG. 1 , the SMF is connected via a connector 15, and thus, along with the input of CW light from the LD 13, the input and output of optical signals are performed via one side of the chip substrate of the PIC 20. The length of the Modulator 21 in the optical axis direction from the input end where the CW light is input to the output end where the transmitted optical signal is output is much longer than the length of the optical receiver 16 including the PD 22. This is particularly noticeable when a Mach-Zehnder interferometer (MZI) type modulator utilizing the electro-optic effect is used. For example, while the length of the MZI type modulator in the optical axis direction is several millimeters, the length of the optical receiver 16 including the PD 22 is at most several tens to hundreds of micrometers. In conventional optical transceivers, the optical transmitter 14 including four parallel Modulators 21 and the optical receiver 16 including four parallel PDs 22 are arranged in parallel so that the input and output of optical signals are concentrated on one side of the chip substrate of the PIC 20. Therefore, the length of the PIC 20 in the optical axis direction depends on the length of the optical transmitter 14, i.e., the length of the modulator, and as the chip size of the PIC 20 increases, there is space on the optical receiver 16 side where no optical circuit elements are mounted, resulting in a problem of poor mounting efficiency of the optical device.

[0006] Chongjin Xie, et al, “Real-Time Demonstration of Silicon-Photonics-Based QSFP-DD 400GBASE-DR4 Transceivers for Datacenter Applications,” T3H.5, OFC2020.

[0007] One embodiment of the present invention is an optical device in which an optical transmitter including a plurality of optical modulators and an optical receiver including a plurality of photodetectors are integrated on a chip substrate, and is characterized in that the transmitter and receiver are arranged in series in the optical axis direction of the optical modulator.

[0008] The input and output of optical signals to the optical transmitter and the input of optical signals to the optical receiver can be concentrated on one side of the chip substrate.

[0009] This configuration eliminates the space on the optical receiver side where no optical circuit elements are mounted, reducing the chip size and improving the mounting efficiency of optical devices.

[0010] FIG. 1 is a diagram showing the configuration of a conventional optical transceiver, FIG. 2 is a diagram showing the configuration of a PIC in a conventional optical transceiver, FIG. 3 is a diagram showing the configuration of a PIC in an optical transceiver according to a first embodiment, FIG. 4 is a diagram showing the configuration of a PIC in an optical transceiver according to a second embodiment, FIG. 5 is a diagram showing the configuration of a PIC in an optical transceiver according to a third embodiment, and FIG. 6 is a diagram showing the configuration of a PIC in an optical transceiver according to a fourth embodiment.

[0011] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, an optical transceiver that transmits and receives optical signals using four parallel SMFs will be described as an example, but there is no limit to the number of parallel SMFs, and this embodiment can be applied regardless of the modulation method.

[0012] FIG. 3 shows the configuration of a PIC in an optical transceiver according to a first embodiment. This is an example of an optical transceiver 10 that transmits and receives optical signals using four parallel SMFs. In the PIC 30, an optical transmitter TX and an optical receiver RX, which are optical devices in the optical system, are arranged in series along the optical axis of an optical modulator (Mod) 31a. Continuous wave light output from an LD 13 is branched into four paths by the optical transmitter TX and supplied to four Modulators 31. The continuous wave light is modulated by an electrical signal supplied from a driver circuit 12 and output as a transmission optical signal.

[0013] As with conventional optical transceivers, the input and output of optical signals are concentrated on one side of the chip substrate of the PIC 30. Therefore, received optical signals from the SMF are input to the optical receiver RX via an optical waveguide formed in the optical transmitter TX. The received optical signals are photoelectrically converted by the photodetector (PD) 32a.

[0014] This configuration eliminates the space where no optical circuit elements are mounted, which was previously formed on the side of the optical receiver RX, thereby reducing the chip size of the PIC 30 and improving mounting efficiency.

[0015] FIG. 4 shows the configuration of a PIC in an optical transceiver according to a second embodiment. This is an example of an optical transceiver 10 that transmits and receives optical signals using four parallel SMFs. In the PIC 40, an optical transmitter TX and an optical receiver RX, which are optical devices in the optical system, are arranged in series along the optical axis of an optical modulator (Mod) 41a. The input and output of optical signals are concentrated on one side of the chip substrate of the PIC 40. The CW light output from the LD 13 bypasses the optical transmitter TX and is input to an optical waveguide formed in the optical receiver RX. The CW light is then branched into four paths in the optical transmitter RX and supplied to the four Modulators 41 of the optical transmitter TX. The CW light is modulated by an electrical signal supplied from a driver circuit 12 and output as a transmission optical signal.

[0016] On the other hand, the received optical signal from the SMF is input to the optical receiver RX via an optical waveguide formed in the optical transmitter TX, as in Example 1. The received optical signal is photoelectrically converted by a photodetector (PD) 42a.

[0017] This configuration eliminates the space where no optical circuit elements are mounted, which was previously formed on the side of the optical receiver RX, thereby reducing the chip size of the PIC 40 and improving mounting efficiency.

[0018] Furthermore, the optical waveguide from the input port of the CW light to the input end of the Modulator 41 and the optical waveguide from the input port of the received optical signal to the input end of the PD 42 are arranged so as not to cross each other. Therefore, compared to the first embodiment, a received optical signal with a low optical power can be input to the optical receiver RX with low loss.

[0019] FIG. 5 shows the configuration of a PIC in an optical transceiver according to a third embodiment. This is an example of an optical transceiver 10 that transmits and receives optical signals using four parallel SMFs. In the PIC 50, an optical transmitter TX and an optical receiver RX, which are optical devices in the optical system, are arranged in series along the optical axis of an optical modulator (Mod) 51a. The CW light output from the LD 13 is branched into four paths in the optical transmitter TX and supplied to the four Mods 51. The CW light is modulated by an electrical signal supplied from the driver circuit 12 and output as a transmission optical signal.

[0020] The input and output of optical signals are concentrated on one side of the chip substrate of the PIC 50. Therefore, received optical signals from the SMF are input to the optical receiver RX via an optical waveguide formed to bypass the optical transmitter TX. Specifically, the optical waveguide is disposed on the outside of one side (bottom side) of the optical integrated circuit that constitutes the optical transmitter TX. The received optical signal is photoelectrically converted by a photodetector (PD) 52a.

[0021] This configuration eliminates the space that was previously formed on the optical receiver RX side where no optical circuit elements were mounted, thereby reducing the chip size of the PIC 50 and improving mounting efficiency.

[0022] Furthermore, the optical waveguide from the input port of the CW light to the input end of the Modulator 51 and the optical waveguide from the input port of the received optical signal to the input end of the PD 52 are arranged so as not to cross each other. Therefore, compared to the first embodiment, a received optical signal with a low optical power can be input to the optical receiver RX with low loss.

[0023] Furthermore, four parallel SMFs for transmission and four parallel SMFs for reception can be grouped together and connected between the PIC 50 and the connector 15 .

[0024] FIG. 6 shows the configuration of a PIC in an optical transceiver according to a fourth embodiment. This is an example of an optical transceiver 10 that transmits and receives optical signals using four parallel SMFs. In the PIC 60, an optical transmitter TX and an optical receiver RX, which are optical devices in the optical system, are arranged in series along the optical axis of an optical modulator (Mod) 61a. Continuous wave light output from the LD 13 is branched into four paths in the optical transmitter TX and supplied to the four Mods 61. The continuous wave light is modulated by an electrical signal supplied from a driver circuit 12 and output as a transmission optical signal.

[0025] The input and output of optical signals are concentrated on one side of the chip substrate of the PIC 60. Therefore, received optical signals from the SMF are input to the optical receiver RX via an optical waveguide formed to bypass the optical transmitter TX. Specifically, optical waveguides are arranged on the outside of two sides (top and bottom sides) of the optical integrated circuit that constitutes the optical transmitter TX. The received optical signals are photoelectrically converted by a photodetector (PD) 62a.

[0026] This configuration eliminates the space that was previously formed on the side of the optical receiver RX where no optical circuit elements were mounted, thereby reducing the chip size of the PIC 60 and improving mounting efficiency.

[0027] Furthermore, the optical waveguide from the input port of the CW light to the input end of the Modulator 61 and the optical waveguide from the input port of the received optical signal to the input end of the PD 62 are arranged so as not to cross each other. Therefore, compared to the first embodiment, a received optical signal with a low optical power can be input to the optical receiver RX with low loss.

[0028] Furthermore, by arranging the optical path through which CW light enters the optical transmitter TX at the center of the parallel-arranged Mod61, the two parallel SMFs for transmission and the two parallel SMFs for reception can be grouped together and arranged symmetrically around the optical path through which CW light enters.

[0029] 10 Optical transceiver 11 DSP chip 12 Driver circuit 13 Laser diode (LD) 14 Optical transmitter (TX) 15 Connector 16 Optical receiver (RX) 17 Amplifier (TIA) 20, 30, 40, 50, 60 Optical integrated circuit (PIC) 21, 31, 41, 51, 61 Optical modulator (Mod) 22, 32, 42, 52, 62 Photodetector (PD)

Claims

1. An optical device in which an optical transmitter including multiple optical modulators and an optical receiver including multiple photodetectors are integrated on a chip substrate, characterized in that the optical transmitter and the optical receiver are arranged in series in the optical axis direction of the optical modulator.

2. The optical device according to claim 1, wherein the input and output of optical signals to said optical transmitter and the input of optical signals to said optical receiver are concentrated on one side of said chip substrate.

3. An optical device as described in claim 1 or 2, characterized in that the optical waveguide from the input port of CW light to the optical transmitter to the optical modulator and the optical waveguide for inputting an optical signal to the optical receiver are arranged so as not to intersect.

4. An optical device according to claim 1 or 2, characterized in that an optical waveguide for inputting an optical signal to said optical receiver is arranged from one side of said chip substrate so as to bypass said optical transmitter.

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