CN113917621B

CN113917621B - PIC chip, optical module and optical network equipment

Info

Publication number: CN113917621B
Application number: CN202010648388.1A
Authority: CN
Inventors: 锁靖; 罗曼·布雷诺; 陈文君
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-07-07
Filing date: 2020-07-07
Publication date: 2023-04-18
Anticipated expiration: 2040-07-07
Also published as: WO2022007585A1; CN113917621A

Abstract

The invention is suitable for the technical field of communication and provides an optical integrated PIC chip. The PIC chip is applied to a single-fiber bidirectional optical component and comprises two optical waveguides. The first end of one of the optical waveguides is used for receiving a transmitting-end optical signal input by the laser LD; the other end of the optical waveguide is used for emitting the light signal at the transmitting end through the optical fiber and receiving the light signal at the receiving end input by the optical fiber, or one end of the other optical waveguide is used for emitting the light signal at the transmitting end through the optical fiber and receiving the light signal at the receiving end input by the optical fiber; the two optical waveguides are partially coupled, and the length of the partial coupling enables the receiving optical signal to be emitted from the other end of the other optical waveguide. The PIC chip coupling part provided by the invention can realize polarization state processing and filtering simultaneously, thereby simplifying the structure of the optical transceiving component and reducing the loss of optical signals.

Description

PIC chip, optical module and optical network equipment

Technical Field

The invention relates to the technical field of optical communication, in particular to a PIC chip, an optical module and optical network equipment.

Background

At present, mature Passive Optical Network (PON) systems such as Ethernet Passive Optical Network (EPON) and Gigabit Passive Optical Network (GPON) have started large-scale deployment worldwide, and fiber to the home is realized. The downlink rate of the GPON/EPON is 2.5Gbps or 1.25Gbps, and the uplink rate is 1.25Gbps. However, with the development of services such as high definition video and network cloud disk, the demand of users for higher bandwidth is increasing, and the deployment of XG (S) -PON, i.e., PON network with 10Gbps downlink speed, has been proposed.

Fig. 1 shows a general structure of a PON system. Generally, a Passive Optical Network system includes an Optical Line Terminal (OLT) located at a central office, a Passive Optical Splitter (POS) for branching/coupling, and a plurality of Optical Network Units (ONUs), and all Optical fiber links from the OLT to the ONUs are called Optical Distribution Networks (ODNs). The direction from OLT to ONU is called the downstream direction, and a 1490nm center wavelength is adopted in the G/EPON network, and a 1577nm center wavelength is adopted in the XG (S) -PON. The direction from the ONU to the OLT is called the upstream direction, and a 1310nm center wavelength is used in the G/EPON network, and a 1270nm center wavelength is used in the XG (S) -PON.

At present, an OLT side Optical component accessed to a PON network is mainly based on a Bi-Directional Optical Sub-Assembly (BOSA) structure. As shown in fig. 2, a Laser Diode (LD) is packaged at a transmitting end into an optical transmission module 1 in fig. 2 by using a Transistor Outline-Can (TO-Can) mode, an amplified Photodetector (PD) is packaged at a receiving end into an optical receiving module 2, and a fiber is coupled and aligned with a Wavelength Division multiplexing filter (WDM) 3 through a fiber ferrule 4. WDM transmits a transmit optical signal from LD to fiber and a receive optical signal from fiber to PD. All the components in fig. 2 are fixed by a case and assembled to form a BOSA. The BOSA contains more components, and the packaging process flow is complex.

Disclosure of Invention

The embodiment of the invention provides a PIC chip, an optical module and optical network equipment, and aims to solve the problems of more BOSA components and complex structure in the prior art.

In a first aspect, the present application provides an optical integrated PIC chip, which is applied to a single-fiber bidirectional optical component, and includes a first optical waveguide and a second optical waveguide, wherein a first end of the first optical waveguide is used for receiving a first optical signal input by a laser LD, and a first end of the second optical waveguide is connected to an optical detector PD; the second end of the first optical waveguide is used for outputting the first optical signal to the optical fiber and receiving a second optical signal input by the optical fiber, or the second end of the second optical waveguide is used for emitting the first optical signal through the optical fiber and receiving the second optical signal input by the optical fiber; the first optical waveguide and the second optical waveguide are partially coupled, the length of the partial coupling enabling the second optical signal to exit from the first end of the second optical waveguide.

According to the scheme, the transmitting end optical signal and the receiving end optical signal can be emitted from different waveguides by specially designing the length of partial coupling between the optical waveguides, and different polarization states of the receiving end optical signal can be processed simultaneously, so that the single-fiber bidirectional of the optical transceiving component is realized, the number of devices can be reduced, and the structure of the optical transceiving component is simplified. Meanwhile, single-ended reception at the PD side can be realized, and optical signal loss is reduced.

With reference to the first aspect, in some possible implementation manners, after the second optical signal enters the first optical waveguide or the second optical waveguide, a third optical signal and a fourth optical signal with different polarization states are separated, and when the second end of the first optical waveguide is used to emit the first optical signal through the optical fiber and receive the second optical signal input by the optical fiber, the length of partial coupling is N times of a coupling period of the first optical signal, M +0.5 times of a coupling period of the third optical signal, and T +0.5 times of a coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1. With this embodiment, the first optical signal is coupled multiple times before exiting the second end of the first optical waveguide, which receives the second optical signal from the optical fiber. Therefore, different polarization states of the second optical signal are coupled for multiple times and then are emitted from the first end of the second optical waveguide, meanwhile, because the length of the coupling part does not meet the multiple relation of the coupling period, interference signals from the optical fiber are filtered, and polarization state processing and filtering effects are achieved.

With reference to the first aspect, in other possible implementation manners, when the second end of the second optical waveguide is configured to exit the first optical signal through the optical fiber and receive the second optical signal input by the optical fiber, the length of the partial coupling is N +0.5 times of a coupling period of the first optical signal, M times of a coupling period of the third optical signal, and T times of a coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1. Through the implementation mode, the second end of the second optical waveguide emits the first optical signal through the optical fiber and receives the second optical signal from the optical fiber, and the second optical signal is still emitted from the first end of the second optical waveguide after being coupled for multiple times. Therefore, the first optical signal and the second optical signal can ensure single-fiber bidirectional, and meanwhile, interference signals of other wavelengths can be filtered out, so that processing of different polarization states of the second optical signal is realized.

It should be noted that, in the present application, the integer multiple and the integer +0.5 times of the coupling period are both theoretical values or optimal values, that is, theoretically, a first optical signal with full power can be emitted from the right side of the first optical waveguide, and a second optical signal with full power can be received from the left side of the second optical waveguide. In practical operation, some errors are allowed, for example, the length of the coupling region is actually 6.99 times of the coupling period of the first optical signal, 5+0.49 times of the coupling period of the third optical signal, and 4+0.49 times of the coupling period of the fourth optical signal, which can still be achieved. It should be understood that the present embodiment is not limited thereto, as long as the coupling region length is designed to simultaneously implement polarization state processing and wavelength division multiplexing within the acceptable range of the optical performance loss.

With reference to the third aspect, in some possible implementations, the first optical waveguide and the second optical waveguide adopt a single-layer structure, that is, the first optical waveguide and the second optical waveguide are located on the same horizontal plane, so that the two waveguides adopt the same manufacturing material, and the manufacturing process is simpler.

With reference to the first aspect, in some possible implementation manners, a double-layer substrate is disposed in the PIC chip, the first optical waveguide is formed on an upper substrate of the double-layer substrate, the second optical waveguide is formed on a lower substrate of the double-layer substrate, and a cross section of the first optical waveguide is square. Therefore, the polarization state of the second optical signal can not be distinguished after the second optical signal enters the first optical waveguide, and the second optical signal is uniformly processed.

With reference to the first aspect, in other possible implementation manners, the partial coupling between the first optical waveguide and the second optical waveguide means that a gap is formed between partial waveguides of the first optical waveguide and the second optical waveguide, and the gap is used for enabling optical mode fields of the first optical waveguide and the second optical waveguide to generate an evanescent coupling effect. The first optical waveguide and the second optical waveguide are provided with a gap, and the design of the gap ensures that the optical signals can generate mutual evanescent coupling effect between the two waveguides. Thus, the optical signal can be continuously coupled between the two waveguides and output from the predetermined optical waveguide port.

With reference to the first aspect, in some possible implementations, the first optical waveguide and the second optical waveguide are both silicon waveguides with a width of 500nm and a thickness of 220nm, and a gap between a part of the waveguides of the first optical waveguide and the second optical waveguide is 100 to 500nm. The gap between the first optical waveguide and the second optical waveguide is related to the waveguide material and the cross-sectional structure, and when the two waveguides are made of silicon waveguide material, the gap can be designed to be any value between 100 nm and 500nm.

With reference to the first aspect, in some possible implementations, the thickness of the silicon waveguide substrate is greater than 220nm, so that the optical signal is limited more and the power loss of the optical signal is reduced.

With reference to the first aspect, in some possible implementations, the first optical waveguide is a silicon nitride waveguide, and/or the second optical waveguide is a silicon waveguide. It should be understood that reference herein to waveguide material is to the core material of the waveguide. In other possible implementations, the first optical waveguide and the second optical waveguide are both silicon waveguides. Different waveguide materials are designed to match with different waveguide widths and thicknesses, so that a better coupling effect is achieved.

With reference to the first aspect, in other possible implementations, the first optical signal wavelength is 1310nm or 1270nm; the wavelength of the second optical signal is 1490nm or 1577nm.

With reference to the first aspect, in some possible implementations, the PIC chip further includes: a laser LD connected to a first end of the first optical waveguide for generating a first optical signal; the optical detector PD is connected with the first end of the second optical waveguide and is used for receiving a second optical signal output by the second optical waveguide; a first mode field converter (SSC) between the LD and the first optical waveguide; a second SSC between the optical fiber and the first optical waveguide or between the optical fiber and the second optical waveguide for matching an optical mode field of the optical waveguide with an optical mode field of the optical fiber; and the trans-impedance amplifier TIA is connected with the PD through a circuit and is used for amplifying the electrical signal after the optical signal conversion. Therefore, the PIC chip integrates the light emitting component and the light receiving component at the same time, and can be used as a complete light receiving and transmitting component to be applied to an optical module.

With reference to the first aspect, in another possible implementation manner, a pillar is etched on an LD side of the waveguide substrate to support a laser chip, and a height of the pillar is selected to align a light exit of the laser with a center height of a port of the first optical waveguide. In this way, the optical signal exiting the laser can enter the first optical waveguide with a greater power.

In a second aspect, the present application provides optical transceiver components, including the PIC chip as described in the first aspect and any possible implementation manner thereof, and further including a laser LD connected to a first end of the first optical waveguide for generating a first optical signal; the optical detector PD is connected with the first end of the second optical waveguide and is used for receiving a second optical signal output by the second optical waveguide; a first mode field converter (SSC) between the LD and the first optical waveguide; a second SSC between the optical fiber and the first optical waveguide or between the optical fiber and the second optical waveguide for matching an optical mode field of the optical waveguide with an optical mode field of the optical fiber; and the trans-impedance amplifier TIA is connected with the PD through a circuit and is used for amplifying the electrical signal after the optical signal conversion. In this way, the PIC chip is used as a chip of the integrated optical waveguide, and is only used as a part of the optical transceiver module, and constitutes a complete optical transceiver module together with other modules.

In a third aspect, the present application provides methods for transceiving optical signals, where a first optical signal input by a laser LD is received through a first end of a first optical waveguide, and a second optical signal received from an optical fiber is output to a photodetector PD through a first end of a second optical waveguide; outputting the first optical signal to an optical fiber through a second end of the first optical waveguide and receiving a second optical signal input by the optical fiber, or emitting the first optical signal out of the optical fiber through a second end of the second optical waveguide and receiving the second optical signal input by the optical fiber; the first optical waveguide and the second optical waveguide are partially coupled to cause the second optical signal to exit from the first end of the second optical waveguide.

With reference to the third aspect, in some possible implementation manners, after a second optical signal enters the first optical waveguide or the second optical waveguide, the third optical signal and the fourth optical signal having different polarization states are separated, and the second optical signal is emitted from the first end of the second optical waveguide through partial coupling between the first optical waveguide and the second optical waveguide, including:

when the first optical signal is emitted from the optical fiber through the second end of the first optical waveguide and the second optical signal input by the optical fiber is received, the length of the partial coupling is N times of the coupling period of the first optical signal, M +0.5 times of the coupling period of the third optical signal, and T +0.5 times of the coupling period of the fourth optical signal, wherein N, M, and T are integers greater than or equal to 1.

With this embodiment, the first optical signal is coupled multiple times before exiting the second end of the first optical waveguide, which receives the second optical signal from the optical fiber. Therefore, different polarization states of the second optical signal are coupled for multiple times and then are emitted from the first end of the second optical waveguide, meanwhile, because the length of the coupling part does not meet the multiple relation of the coupling period, interference signals from the optical fiber are filtered, and polarization state processing and filtering effects can be achieved simultaneously.

With reference to the third aspect, in other possible implementation manners, when the first optical signal is emitted from an optical fiber through the second end of the second optical waveguide and the second optical signal input by the optical fiber is received, the length of the partial coupling is N +0.5 times of a coupling period of the first optical signal, M times of a coupling period of the third optical signal, and T times of a coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1.

Through the implementation mode, the second end of the second optical waveguide emits the first optical signal through the optical fiber and receives the second optical signal from the optical fiber, and the second optical signal is still emitted from the first end of the second optical waveguide after being coupled for multiple times. Therefore, the first optical signal and the second optical signal can ensure single-fiber bidirectional, and meanwhile, interference signals of other wavelengths can be filtered out, so that processing of different polarization states of the second optical signal is realized.

With reference to the third aspect, in some possible implementations, the partial coupling between the first optical waveguide and the second optical waveguide means that a gap is formed between partial waveguides of the first optical waveguide and the second optical waveguide, and the gap is used for enabling optical mode fields of the first optical waveguide and the second optical waveguide to generate an evanescent coupling interaction. The first optical waveguide and the second optical waveguide are provided with a gap, and the design of the gap ensures that the optical signals can generate mutual evanescent coupling effect between the two waveguides. Thus, the optical signal can be continuously coupled between the two waveguides to be output from the predetermined optical waveguide port.

With reference to the third aspect, in another possible implementation manner, both the first optical waveguide and the second optical waveguide are silicon waveguides, and a gap between a part of the waveguides of the first optical waveguide and the second optical waveguide is 100 to 500nm. Thus, the optical signal can be continuously coupled between the two waveguides and finally output from the preset port.

In a fourth aspect, the present application provides some optical modules, including a housing structure, a light source driver, a PIC chip as described in any one of the first aspect and any one of the possible implementations thereof, and a signal processor, wherein the light source driver is configured to drive a laser LD to generate a light beam with a specific wavelength; and the signal processor is used for processing the optical signals received by the PIC chip, and the light source driver, the PIC chip and the signal processor are packaged in the shell structure.

In a fifth aspect, the present application provides some optical network devices, including the optical module in the fourth aspect, and further including a communication port, configured to be inserted into the optical module, and send an optical signal of the optical network device to another network device through the optical module, and/or receive an optical signal sent by the another network device.

In a sixth aspect, the present application provides some passive optical network systems, including the optical network device according to the fifth aspect, and further including an optical distribution network, where the optical distribution network is connected to the optical network device; and a plurality of optical network units, which receive the downlink optical signal sent by the optical network equipment through an optical distribution network; and/or sending an upstream optical signal to the optical network device.

The PIC chip, the optical module, the related equipment and the system provided by the application can enable the transmitting end optical signal and the receiving end optical signal to be emitted from different waveguides by specially designing the length of partial coupling between the optical waveguides, filter out interference signals, and simultaneously process different polarization states of the receiving end optical signal, thereby not only realizing single-fiber bidirectional and filtering of the optical transceiving component, but also reducing the number of devices and simplifying the structure of the optical transceiving component. Meanwhile, single-ended reception at the PD side can be realized, and optical signal loss is reduced.

Drawings

Fig. 1 is a schematic diagram of a structure of a PON network system;

FIG. 2 is a schematic diagram of a package structure of a BOSA in the prior art;

fig. 3 is a schematic structural diagram of an optical circuit integrated chip PIC provided in an embodiment of the present application;

FIG. 4 is a schematic optical path diagram of a waveguide coupling region provided in an embodiment of the present application;

FIG. 5 is a schematic optical path diagram of another waveguide coupling region provided in embodiments of the present application;

fig. 6A is a top view of a PIC chip provided in an embodiment of the present application;

FIG. 6B is a right side cross-sectional view of the coupling region in the PIC chip shown in FIG. 6A;

fig. 7A is a top view of another PIC chip provided in an embodiment of the present application;

FIG. 7B is a front view of the PIC chip shown in FIG. 7A;

fig. 7C is a waveguide cross-sectional view of the PIC chip of fig. 7A and 7B;

FIG. 8 is a schematic optical path diagram of another waveguide coupling region provided in an embodiment of the present application;

FIG. 9 is a cross-sectional view of yet another optical waveguide provided in accordance with an embodiment of the present application;

fig. 10 is a flowchart of an optical signal processing method according to an embodiment of the present disclosure;

fig. 11 is a flowchart of another optical signal processing method according to an embodiment of the present disclosure;

fig. 12 is a schematic structural diagram of an optical module according to an embodiment of the present application;

fig. 13 is a schematic structural diagram of an optical network device according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

One of the core elements of fiber optic communications is the conversion of optical to electrical signals. The optical fiber communication uses the optical signal carrying information to transmit in the optical fiber, and the information transmission with low cost and low loss can be realized by using the passive transmission characteristic of the light in the optical fiber. The information processing devices such as computers use electrical signals, which require the interconversion between electrical signals and optical signals during the signal transmission process. The optical module realizes the photoelectric conversion function in the technical field of optical fiber communication, and the interconversion of optical signals and electric signals is the core function of the optical module. In the architecture of the existing optical network, in order to save optical fiber resources, photoelectric devices all adopt a single-fiber bidirectional structure, that is, a transmitting component and a receiving component are packaged in the same device, that is, a single-fiber bidirectional device, such as a single-fiber bidirectional optical module.

The single-fiber bidirectional optical module realizes the transmission of bidirectional information in one optical fiber by using a wavelength division multiplexing technology, and is increasingly adopted in a PON system due to the fact that optical fiber resources can be saved. The BOSA is a core component for integrating light emission and reception in the BOSA.

In order to reduce the process complexity of the optical module and improve the coupling efficiency of the device, a Photonic Integrated Circuit (PIC) may be introduced into the optical transceiver module. By using the optical circuit integration technology of the PIC chip, the assembly and coupling processes faced by discrete optical elements can be avoided, and the miniaturization of the equipment can be realized. However, the space advantage of the optical component with a three-dimensional structure is not available, and the cross section of the waveguide of the on-chip integrated optical waveguide structure is generally rectangular, so that the optical signal can be excited to generate two polarization states after entering the waveguide, and therefore, compared with the conventional optical component, the on-chip integrated optical waveguide chip needs to additionally solve the problem of the polarization state generated when the receiving-end optical signal enters the chip. The asymmetry of the vibration direction of the wave to the propagation direction is called polarization, the light wave is an electromagnetic wave, and the propagation direction of the light wave is the propagation direction of the electromagnetic wave; in the propagation process of light waves, an Electric vibration vector E and a Magnetic vibration vector H are generated, and a polarization state of the Electric vibration vector E perpendicular to the propagation direction of electromagnetic waves is generally called a Transverse Electric wave (TE), and a polarization state of the Magnetic vibration vector H perpendicular to the propagation direction of electromagnetic waves is generally called a Transverse Magnetic wave (TM).

At present, because the waveguide section of the integrated chip PIC is generally rectangular, an optical signal entering the waveguide can excite and generate two polarization states of TE and TM, wherein the loss of TE during transmission in the waveguide is small, the loss of TM during transmission in the waveguide is large, and the refractive indexes of the waveguides corresponding to TE and TM are also different. An optical signal entering a waveguide from an optical fiber needs to pass through a Polarization beam Splitter and Rotator (PSR) to separate light components of TE and TM Polarization states, and then convert the light component of the TM Polarization state into light of the TE Polarization state through a process. Two beams of light need to be filtered through two wavelength division multiplexing filters WDM respectively, wherein one of the two beams of light is used for separating an optical signal component with a wavelength at a receiving side and then is transmitted to a Photo Detector (PD) with two ends receiving light; and the other is used for separating the optical signal component with the wavelength of the receiving side, and simultaneously coupling and sending the optical signal wavelength emitted by a Laser Diode (LD) to the outlet side of the optical fiber. It follows that in order to handle both polarisation states and wavelength splitting, at least three processing devices are typically required, including one PSR and two WDM's. It should be appreciated that more devices result in greater optical power loss; meanwhile, the two WDM should keep consistent in optical signal processing, which is difficult to implement; furthermore, the performance of a double-ended reception PD is slightly worse than that of a single-ended reception PD. The above problems need to be solved by a new structural design of the optical integrated circuit.

Fig. 3 is a schematic structural diagram of an optical circuit integrated chip PIC according to an embodiment of the present application. As shown in fig. 3, the PIC chip includes a first optical waveguide and a second optical waveguide. One end of the first optical waveguide is connected to the LD310 and is configured to couple a first optical signal emitted by the LD 310. The other end of the first optical waveguide is connected with the optical fiber and used for emitting the first optical signal through the optical fiber and receiving the second optical signal from the optical fiber. One end of the second optical waveguide is connected to the PD 320 for feeding the second optical signal into the PD. The first optical waveguide and the second optical waveguide of the PIC chip coupling region are partially coupled, the coupled portion being labeled 350. The coupling region 350 represents in this embodiment that portion of the optical waveguide between the first optical waveguide and the second optical waveguide that is parallel and has the smallest gap. The gap between the two optical waveguides is small enough, so that the optical mode fields of the two optical waveguides can generate mutual evanescent coupling effect; and the length of the coupling region is designed to satisfy a certain condition, so that the first optical signal from the LD side can be emitted from the other end of the first optical waveguide, and the second optical signal (no matter in TE state or TM state) received from the optical fiber can be emitted from the PD end of the second optical waveguide.

As an example, the LD310 and the first optical waveguide are connected through the SSC 330, and the SSC 430 may match an optical mode field of the LD310 with an optical mode field of the first optical waveguide, so as to achieve the best coupling effect, and a first optical signal emitted by the LD310 may enter the first optical waveguide with the maximum power.

As another example, the first optical waveguide is coupled to the optical fiber via an SSC 340, where the SSC 340 may match the optical mode field of the first optical waveguide to the optical mode field of the optical fiber to achieve the best coupling, the first optical signal is emitted through the optical fiber with maximum power, and the second optical signal is received with maximum power.

As an example, the PIC chip further includes a trans-impedance amplifier (TIA) 360 disposed after the PD 320 for power amplifying the received optical signal.

It should be noted that the other end of the second optical waveguide may also be connected to an optical fiber, as long as it is ensured that both the reception and the transmission of the optical signal pass through the same port, which is not limited in this application.

It should be further noted that the PD 320, SSC 330, SSC 340 in this embodiment may be integrated directly on the PIC chip. Other components including the LD310, the optical fiber, and the TIA360 may be hybrid integrated by means of external mounting.

In this embodiment, by setting partial coupling between two waveguides in the PIC chip, PD is changed from double-ended reception to single-ended reception, which not only can simultaneously implement polarization processing and filtering, but also can simplify the structure of the optical transceiver module and reduce the optical signal loss.

Fig. 4 is a schematic optical path diagram of a waveguide coupling region according to an embodiment of the present disclosure. As shown in fig. 4, the coupling region is formed by two parallel optical waveguides, the upper optical waveguide being referred to as the first optical waveguide and the lower optical waveguide being referred to as the second optical waveguide. It should be understood that the first optical waveguide and the second optical waveguide in this embodiment refer to only the coupling region 350 of two optical waveguides in the PIC chip shown in fig. 3. The first optical waveguide and the second optical waveguide have a gap therebetween that is small enough such that the optical mode fields of the two optical waveguides produce mutual evanescent coupling. The coupling period of the optical beam is directly related to its refractive index in the optical waveguide. The coupling period is the waveguide length required for a light beam with the wavelength lambda to be completely coupled from the first optical waveguide to the second optical waveguide and then to be re-coupled back to the first optical waveguide; conversely, it is also possible to have the required waveguide length for the light beam with wavelength λ to be completely coupled from the second optical waveguide to the first optical waveguide and then to be recoupled back to the second optical waveguide. Therefore, the refractive index of the optical signals with different wavelengths and the refractive index of the optical signals with the same wavelength and different polarization states are different when the optical signals with the same wavelength and different polarization states are transmitted in the coupling region, and the coupling period is also different.

The laser LD emits light with a wavelength of lambda ₁ Is coupled into the first optical waveguide, and excites a first optical signal in a TE polarization state; the other end of the first optical waveguide transmits the first optical signal through the optical fiber and receives the first optical signal from the optical fiber with the wavelength of lambda ₂ And the polarization state of the second optical signal is randomly distributed when the second optical signal is propagated in the optical fiber, and after the second optical signal is coupled into the first optical waveguide, a third optical signal with the polarization state of TE and a fourth optical signal with the polarization state of TM are excited.

In this embodiment, the length of the coupling region is designed to be N times of the coupling period of the first optical signal, M +0.5 times of the third optical signal, and T +0.5 times of the fourth optical signal. At this time, since the length of the coupling region is an integral multiple of the coupling period of the first optical signal, it can be finally emitted from the first optical waveguide; since the length of the coupling region is +0.5 times the integer of the third optical signal and the fourth optical signal, both the third optical signal and the fourth optical signal can be emitted from the other side of the second optical waveguide, as shown in fig. 4. And then the third optical signal and the fourth optical signal enter the PD to be converted into electric signals, and the transmission process of the receiving side light is completed. Because other interference information from the optical fiber does not satisfy the multiple relation (no matter the multiple or the integer is plus 0.5 times) of the coupling period, the interference information cannot be emitted from the left side of the second optical waveguide and enters the PD, and therefore filtering is achieved. Wherein N, M and T are integers which are more than or equal to 1.

It should be noted that the design value of the gap between the first optical waveguide and the second optical waveguide is related to the waveguide material and the cross-sectional structure. This is not limited in this application.

Fig. 5 is a schematic optical path diagram of another waveguide coupling region provided in the embodiments of the present application. The coupling region is still formed by two parallel optical waveguides, as in fig. 4, the laser LD emitting light with a wavelength λ ₁ Is coupled directly into the first optical waveguide to excite the first optical signal in the TE polarization state. Unlike fig. 4, in this embodiment, the first optical signal is transmitted through the optical fiber via the other end of the second optical waveguide, and is received from the optical fiber at the wavelength λ ₂ The second optical signal of (1). When the second optical signal is propagated in the optical fiber, the polarization state is randomly distributed, and after the second optical signal is coupled into the second optical waveguide, a third optical signal with the polarization state being TE and a fourth optical signal with the polarization state being TM are excited. Accordingly, the length of the coupling region is designed to be N +0.5 times the coupling period of the first optical signal, M times the coupling period of the third optical signal, and T times the coupling period of the fourth optical signal. At this time, since the length of the coupling region is +0.5 times of the integral of the coupling period of the first optical signal, it can be finally emitted from the second optical waveguide; since the length of the coupling region is an integral multiple of the third optical signal and the fourth optical signal, both the third optical signal and the fourth optical signal can be emitted from the other side of the second optical waveguide, as shown in fig. 5. Then the third optical signal and the fourth optical signal enter the PD to be converted into electric signals, and the reception is finishedAnd (4) transmitting side light. Wherein N, M and T are integers which are more than or equal to 1.

As an example, λ ₁ Is 1310nm, lambda ₂ Is 1490nm, or λ ₁ Is 1270nm, lambda ₂ Is 1577nm.

The waveguide is made of at least two different materials, wherein the material with a higher refractive index is used as a waveguide core layer, most optical signals are limited in the core layer in the transmission process, and a cladding made of a low-refractive-index material is arranged around the core layer. Typical optical waveguide core materials include silicon, silicon nitride, silicon carbide, silicon oxynitride, silicon oxycarbide, and the like. Fig. 6A shows a top view of a PIC chip provided in an embodiment of the present application. As shown in fig. 6A, the PIC chip has a single-layer waveguide structure, and may be implemented based on a Silicon On Insulator (SOI) technology, where SOI is used as a processing substrate of the PIC chip, and the first optical waveguide 610 and the second optical waveguide 620 are both Silicon waveguides. The first optical waveguide 610 and the second optical waveguide 620 are disposed on the same horizontal plane of the SOI, wherein one end of the first optical waveguide 610 is connected to the LD 630, and the other end is connected to the optical fiber; one end of the second optical waveguide 620 is connected to the PD 640. There is a coupling region 650 between the two waveguides, and the length of the coupling region is designed to be N times of the coupling period of the first optical signal, M +0.5 times of the third optical signal, and T +0.5 times of the fourth optical signal, at this time, the first optical signal is emitted from the right side of the first optical waveguide, and the third optical signal and the fourth optical signal are emitted from the left side of the second optical waveguide, and the coupling process can refer to fig. 4. It should be understood that an optical fiber may also be connected to the other end of the second optical waveguide for transmitting the first optical signal and receiving the second optical signal from the optical fiber, and the coupling process of the first optical signal and the second optical signal may be as shown in fig. 6.

In this embodiment, the transmitting end side of the SOI 600 may be hollowed to etch a pillar for supporting the LD chip, where the height of the pillar makes the light exit of the LD exactly aligned with the cross-sectional center of the first optical waveguide; the integrated PD is connected to a left side end of the second optical waveguide.

Fig. 6B is a right cross-sectional view of the optical waveguide coupling region shown in fig. 6A. The first optical waveguide 610 and the second optical waveguide 620 are integrated into the SOI 600, as shown in fig. 6B, both waveguides have a geometry, width d, and thickness h. The effective refractive index of an optical waveguide is a function of the refractive indices of the waveguide core and cladding, as well as the thickness and width of the waveguide. In PIC chip fabrication techniques, the refractive index of the planar waveguide is generally uniform and difficult to vary along the optical path propagation direction. Therefore, we can generally consider changing the geometrical dimensions of the optical waveguide, for example changing the width d, or changing the thickness h of the waveguide by increasing the substrate thickness. As the waveguide height or width increases, the effective refractive index of the optical signal propagating from the optical fluctuation increases. It should be understood that the widths of the two waveguides may be different, and this embodiment is not limited thereto.

Illustratively, the first optical waveguide and the second optical waveguide are both silicon waveguides 500nm wide and 220nm thick, and the gap between the two waveguides is designed to be any value in the range of 100 to 500nm.

Fig. 7A is a top view of another PIC chip according to an embodiment of the present disclosure. As shown in fig. 7A, the PIC chip has a double-layer waveguide structure, and the double-layer waveguide may be made of different materials, for example, the upper layer waveguide material is Silicon nitride (SiN), and the lower layer waveguide material is SOI. Due to different manufacturing materials, the upper layer optical waveguide and the lower layer optical waveguide have different refractive indexes for transmitted optical signals, and therefore the coupling period of the optical signals is also changed compared with that of a single-layer optical waveguide. Fig. 7A shows a top view of the PIC die, where the first optical waveguide 710 is located on the upper layer of the PIC die and the second optical waveguide 720 is located on the lower layer of the PIC die, as shown in fig. 7A. Illustratively, the first optical waveguide is straight and has no bend in the chip, and the second optical waveguide comprises three portions, 721, 722 and 723 respectively. Part 721 is connected to PD 750 on the left side, and the whole part is located in front of and below the first optical waveguide; the 722 part is connected with the 721 part and the 723 part and is used for separating the first optical waveguide and the second optical waveguide, so that the left sides of the first optical waveguide and the second optical waveguide are provided with sufficient space for integrating the LD 740 and the PD 750; portion 723 forms a coupling region 730 with a corresponding portion of the first optical waveguide for processing the polarization state of the optical signal while achieving wavelength division multiplexing. It should be noted that only the 721, 722 parts of the first waveguide and the second waveguide can be seen in fig. 7A, and the 723 part cannot be seen, because the 723 part is blocked by the corresponding part of the first optical waveguide. Fig. 7B is a front view of the PIC chip, and in fig. 7B, the distance between the first optical waveguide and the second optical waveguide is the coupling distance between the two waveguides, but it should be understood that, in fact, the two waveguides are staggered back and forth except for the coupling region, which is actually much greater than the illustrated distance.

Fig. 7C shows a cross-sectional view of the waveguide within the PIC chip of fig. 7A and 7B. Because the first optical waveguide core layer is made of SiN, the refractive index of optical signals transmitted in the first optical waveguide core layer is smaller than that of silicon materials, and in order to ensure that the optical signals reach the ideal effective refractive index, the thickness of the first optical waveguide is correspondingly increased. For example, the thickness H of the first optical waveguide is 400nm, and the thickness H of the second optical waveguide is still 220nm. The first and second optical waveguides may both have a width d.

In the present embodiment, the length of the coupling region 730 is designed to be N times the coupling period of the first optical signal emitted from the transmitting LD, and simultaneously to be the TE polarization state of the second optical signal received from the optical fiber, i.e., M +0.5 times the coupling period of the third optical signal, and simultaneously to be the TM polarization state of the second optical signal, i.e., T +0.5 times the coupling period of the fourth optical signal. At this time, the wavelength is λ ₁ The first optical signal is incident from the left side of the first optical waveguide, and coupling occurs at the coupling region 730, and the coupling process can be referred to fig. 4, and the first optical signal is emitted from the right side of the first optical waveguide after being coupled for a plurality of times. Wavelength of λ ₂ The second optical signal enters from the right side of the first optical waveguide, a third optical signal with a TE polarization state and a fourth optical signal with a TM polarization state are excited, and the two optical signals are coupled for multiple times between the two waveguides and then are emitted from the left side of the second optical waveguide.

It should be noted that, in the present embodiment, the integral multiple and the integral +0.5 times of the coupling period are both theoretical values or optimal values, that is, theoretically, a first optical signal with full power can be emitted from the right side of the first optical waveguide, and a second optical signal with full power can be received from the left side of the second optical waveguide. In practical operation, certain errors are allowed, for example, the length of the coupling region is actually 6.99 times of the coupling period of the first optical signal, 5+0.49 times of the coupling period of the third optical signal, and 4+0.49 times of the coupling period of the fourth optical signal. It should be understood that the present embodiment is not limited thereto, as long as the coupling region length is designed to simultaneously implement polarization state processing and wavelength division multiplexing within the acceptable range of the optical performance loss.

As an example, the length of the coupling region 730 can also be designed to be N +0.5 times the coupling period of the first optical signal, M times the coupling period of the third optical signal, and T times the coupling period of the fourth optical signal. At this time, referring to fig. 5, the first optical signal is coupled between the two waveguides for multiple times and then exits from the right side of the second optical waveguide, and the TE polarization state and the TM polarization state of the second optical signal are both coupled between the two waveguides for multiple times and then exits from the left side of the second optical waveguide and enters the PD.

Fig. 8 is a schematic optical path diagram of another waveguide coupling region provided in an embodiment of the present application. The waveguide structure is realized based on a double-layer waveguide structure shown in fig. 7A and 7B, in which the upper layer waveguide material is still SiN and the lower layer waveguide material is still SOI. However, in this embodiment, the cross section of the first optical waveguide 810 located at the upper layer is square, that is, the width and the thickness of the first optical waveguide are the same, and are both d, as shown in fig. 9, so the TE polarization state and the TM polarization state are the same, and no distinction treatment is needed. The length of the coupling region is designed to be N times of the coupling period of the first optical signal and is designed to be M +0.5 times of the coupling period of the second optical signal. A first optical signal enters from the left side of the first optical waveguide 810, and exits from the right side of the first optical waveguide 810 after being coupled for an integer number of times between the two waveguides; a second optical signal enters from the right side of the first optical waveguide 810, exits from the left side of the second optical waveguide 820 after being coupled an integer number of times and a half number of times between the two waveguides, and enters the PD.

Illustratively, the width and thickness d of the first optical waveguide is 800nm, the width of the second optical waveguide is 800nm, and the thickness is 220nm.

Exemplarily λ ₁ Is 1310nm, lambda ₂ Is 1490nm, or λ ₁ Is 1270nm, lambda ₂ Is 1577nm.

Fig. 10 is a flowchart of an optical signal processing method according to an embodiment of the present disclosure. As shown in fig. 10, the method includes the following steps.

S1001: the first optical signal input by the laser LD is received through the first end of the first optical waveguide, and the second optical signal received from the optical fiber is output to the photodetector LD through the first end of the second optical waveguide.

For example, the wavelength of the first optical signal is 1310nm, and the wavelength of the second optical signal is 1490nm; for another example, the first optical signal has a wavelength of 1270nm and the second optical signal has a wavelength of 1577nm.

S1002: and outputting the first optical signal to the optical fiber through the second end of the first optical waveguide, and receiving a second optical signal input by the optical fiber.

S1003: the second optical signal is emitted from the first end of the second optical waveguide by partial coupling between the first optical waveguide and the second optical waveguide.

When the first optical signal is output to the optical fiber through the second end of the first optical waveguide and the second optical signal input by the optical fiber is received, the length of the coupling part of the two waveguides is designed to be N times of the coupling period of the first optical signal, M +0.5 times of the coupling period of the third optical signal and T +0.5 times of the coupling period of the fourth optical signal. The third optical signal and the fourth optical signal are different polarization states of the second optical signal. Wherein N, M and T are integers which are more than or equal to 1. In this way, the second optical signal can exit from the first end of the second optical waveguide.

Fig. 11 is a flowchart of another optical signal processing method according to an embodiment of the present disclosure. Different from fig. 10, in this embodiment, the first optical signal is output to the optical fiber through the second end of the second optical waveguide, and the second optical signal input by the optical fiber is received, so that the lengths of the coupling portions of the two waveguides are respectively designed to be N +0.5 times of the coupling period of the first optical signal, M times of the coupling period of the third optical signal, and T times of the coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1.

Fig. 12 is a schematic structural diagram of an optical module according to an embodiment of the present application. The optical module comprises a PIC chip 3 shown in fig. 3, a light source driver 1 and a signal processor 2. The light source driver 1 is connected with a sending end LD310 of the optical module and used for providing power supply for the sending end LD 310; the signal processor 2 is connected to the output of the receiving side for processing the received optical signal. The specific structure of the PIC chip 3 can refer to fig. 3, and details thereof are not repeated here.

Fig. 13 is a schematic structural diagram of an optical network device according to an embodiment of the present application. As shown in fig. 13, the network device includes an optical module 1 and a data processing module 2, where the optical module may be the optical module shown in fig. 12, and the data processing module is configured to process an optical signal received by the optical module from another network device, and send the optical signal processed by the network device out through the optical module.

As an example, the network device may be an OLT device of a PON network system, and the data processing unit 2 of the network device may be configured to process an upstream optical signal from another optical network unit, and/or send an optical signal in an optical fiber received by the OLT to the other optical network unit after being processed by the data processing unit 2.

The embodiment of the present application also protects a PON network system, which can refer to fig. 1, and includes at least one OLT, a plurality of optical splitters, and a plurality of optical network units ONU. Wherein the OLT may be an optical network device shown in fig. 13. .

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the present invention. The terms "first," "second," and the like in the description and claims of the present invention and in the preceding drawings are not used to describe a particular order or sequence. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments described herein are capable of operation in other sequences than described or illustrated herein. Furthermore, the terms "comprises" or "comprising," and any variations thereof, are intended to cover non-exclusive items, for example, items or devices that comprise a list of elements are not necessarily limited to those elements explicitly listed, but may include other elements not explicitly listed that are inherent to such items or devices. As an example, the schematic structure diagram of the PIC chip shown in fig. 4 in the embodiment of the present invention includes, in addition to the LD310, PD 320, SSC 330, SSC 340, coupling area 350 and TIA360 specifically listed in the embodiment, other components that are not explicitly listed but are inherent to the PIC chip, such as electrical traces and the like. The term "and/or" means either of the two cases of front and back connection, such as A and/or B, including A, B, A and B.

While the present application has been described in connection with various embodiments, other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed application, from a review of the drawings, the disclosure, and the appended claims. In the claims, a single hardware or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. An optical integrated PIC chip, the PIC chip is applied to a single-fiber bidirectional optical component, and is characterized by comprising a first optical waveguide and a second optical waveguide, wherein:

the first end of the first optical waveguide is used for receiving a first optical signal input by a laser LD, and the first end of the second optical waveguide is connected with a photodetector PD;

the second end of the first optical waveguide is used for outputting the first optical signal to an optical fiber and receiving a second optical signal input by the optical fiber, or the second end of the second optical waveguide is used for emitting the first optical signal through the optical fiber and receiving the second optical signal input by the optical fiber;

the first optical waveguide and the second optical waveguide are partially coupled, and the length of the partial coupling enables the second optical signal to be emitted from the first end of the second optical waveguide;

when the cross section of the first optical waveguide is square, the length of partial coupling is designed to be N times of the coupling period of the first optical signal and to be M +0.5 times of the coupling period of the second optical signal.

2. The PIC chip of claim 1, wherein when the second optical signal enters the first optical waveguide or the second optical waveguide, a third optical signal and a fourth optical signal with different polarization states are separated, and when the second end of the first optical waveguide is configured to emit the first optical signal through an optical fiber and receive the second optical signal input by the optical fiber, the length of the partial coupling is N times of a coupling period of the first optical signal, M +0.5 times of the coupling period of the third optical signal, and T +0.5 times of the coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1.

3. The PIC chip of claim 1, wherein when the second optical signal enters the first optical waveguide or the second optical waveguide and is split into a third optical signal and a fourth optical signal with different polarization states, when the second end of the second optical waveguide is used to emit the first optical signal through the optical fiber and receive the second optical signal input by the optical fiber, the length of the partial coupling is N +0.5 times of a coupling period of the first optical signal, M times of the coupling period of the third optical signal, and T times of the coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1.

4. The PIC chip of any one of claims 1-3, wherein the first optical waveguide and the second optical waveguide are both silicon waveguides with a width of 500nm and a thickness of 220nm, and a gap between part of the first optical waveguide and the second optical waveguide is 100-500nm.

5. The PIC chip of any one of claims 1 to 3, wherein the partial coupling between the first optical waveguide and the second optical waveguide is:

and a gap is arranged between the first optical waveguide and a part of the second optical waveguide, and the gap is used for generating evanescent coupling effect on optical mode fields of the first optical waveguide and the second optical waveguide.

6. The PIC chip of any one of claims 1 to 3, wherein the first optical waveguide is a silicon nitride waveguide and/or the second optical waveguide is a silicon waveguide.

7. The PIC chip of any one of claims 1 to 3, wherein the first optical signal wavelength is 1310nm or 1270nm; the wavelength of the second optical signal is 1490nm or 1577nm.

8. The PIC chip of any one of claims 1 to 3, further comprising:

a laser LD connected to the first end of the first optical waveguide for generating the first optical signal;

the optical detector PD is connected with the first end of the second optical waveguide and is used for receiving the second optical signal output by the second optical waveguide;

a first mode field converter (SSC) between the LD and the first optical waveguide;

a second SSC located between the optical fiber and the first optical waveguide or between the optical fiber and the second optical waveguide, for matching an optical mode field of the optical waveguide with an optical mode field of the optical fiber;

and the trans-impedance amplifier TIA is connected with the PD through a circuit and is used for amplifying the electrical signal after the optical signal conversion.

9. A method for transmitting and receiving an optical signal, the method comprising:

receiving a first optical signal input by a laser LD through a first end of a first optical waveguide of an optical integrated PIC chip, and outputting a second optical signal received from an optical fiber to a photodetector PD through a first end of a second optical waveguide of the PIC chip;

outputting the first optical signal to an optical fiber through a second end of the first optical waveguide and receiving a second optical signal input by the optical fiber, or emitting the first optical signal out of the optical fiber through a second end of the second optical waveguide and receiving the second optical signal input by the optical fiber;

partially coupling the first optical waveguide and the second optical waveguide to enable the second optical signal to be emitted from a first end of the second optical waveguide;

when the cross section of the first optical waveguide is square, the length of the partial coupling is designed to be N times of the coupling period of the first optical signal and to be M +0.5 times of the coupling period of the second optical signal; the partially coupling the first optical waveguide and the second optical waveguide to cause the second optical signal to exit from the first end of the second optical waveguide includes:

the first optical signal enters from the first end of the first optical waveguide through the partial coupling of the first optical waveguide and the second optical waveguide, and exits from the second end of the first optical waveguide after passing through the integral-time coupling between the first optical waveguide and the second optical waveguide, and the second optical signal enters from the second end of the first optical waveguide and exits from the first end of the second optical waveguide after passing through the integral-time and half-time coupling between the first optical waveguide and the second optical waveguide.

10. The method of claim 9, wherein separating a third optical signal and a fourth optical signal having different polarization states after the second optical signal enters the first optical waveguide or the second optical waveguide, wherein partially coupling the first optical waveguide and the second optical waveguide causes the second optical signal to exit the first end of the second optical waveguide, comprising:

when the first optical signal is emitted from the optical fiber through the second end of the first optical waveguide and the second optical signal input by the optical fiber is received, the length of the partial coupling is N times of the coupling period of the first optical signal, M +0.5 times of the coupling period of the third optical signal, and T +0.5 times of the coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1.

11. The method of claim 10, wherein said causing the second optical signal to exit the first end of the second optical waveguide via a partial coupling between the first optical waveguide and the second optical waveguide further comprises:

when the first optical signal is emitted from the optical fiber through the second end of the second optical waveguide and the second optical signal input by the optical fiber is received, the length of the partial coupling is N +0.5 times of the coupling period of the first optical signal, M times of the coupling period of the third optical signal, and T times of the coupling period of the fourth optical signal, where N, M, and T are integers greater than or equal to 1.

12. The method of any of claims 9 to 10, wherein the partial coupling between the first optical waveguide and the second optical waveguide is:

and a gap is formed between the partial waveguides of the first optical waveguide and the second optical waveguide, and the gap is used for enabling the optical mode fields of the first optical waveguide and the second optical waveguide to generate mutual evanescent coupling effect.

13. The method according to any one of claims 9 to 10, wherein the first optical waveguide and the second optical waveguide are both silicon waveguides with a width of 500nm and a thickness of 220nm, and a gap between part of the waveguides of the first optical waveguide and the second optical waveguide is 100 to 500nm.

14. An optical module comprising a housing structure, a light source driver, a PIC chip according to any one of claims 1 to 8, and a signal processor, wherein,

the light source driver is used for driving the laser LD to generate a light beam with a specific wavelength;

the signal processor is used for processing the optical signals received by the PIC chip,

the light source driver, the PIC chip and the signal processor are packaged in the shell structure.

15. An optical network device, characterized in that it comprises an optical module according to claim 14 and

and the communication port is used for transmitting the optical signal of the optical network equipment to other network equipment through the optical module and/or receiving the optical signal transmitted by other network equipment.

16. A passive optical network system, comprising:

the optical network device of claim 15;

an optical distribution network connecting the optical network device and a plurality of optical network units;

the plurality of optical network units receive downlink optical signals sent by the optical network equipment through the optical distribution network; and/or sending an uplink optical signal to the optical network device.