KR100596406B1 - WDM-PON system with optical wavelength alignment function - Google Patents

Abstract

The present invention relates to a WDM-PON system having an optical wavelength alignment function, the WDM-PON system having an optical wavelength alignment function, comprising: a fixed substrate; A semiconductor chip in which a passive waveguide region exists in front of the active waveguide region using a directional coupling principle of an active waveguide region for generating light and light generated in the active waveguide region; A PLC waveguide formed on the fixed substrate, having a PLC platform formed at one end thereof to surface-bond the semiconductor chip by a manual alignment method, and having a waveguide bragg grating (WBG) formed at a predetermined point; A directional coupler for transmitting optical power by bringing the passive waveguide region into close proximity to the PLC waveguide; A heater electrode formed on the top of the WBG to control the temperature of the WBG; And an optical fiber formed on the silicon substrate at the other end of the PLC waveguide. Accordingly, it is possible to provide a WDM-PON system having an optical wavelength alignment function that can realize optical wavelength alignment in a cost-effective manner.

Description

WDM-PON system with optical wavelength alignment function

1A and 1B are block diagrams of a WDM-PON having an optical wavelength alignment function according to temperature change according to an embodiment of the present invention.

2 is a block diagram showing a logical structure of a WDM-PON according to an embodiment of the present invention.

3 is a plan view showing in detail the structure of the RN-WDMX 240 of FIG.

4 is a plan view showing in detail the structure of the RN-WMUX 250 of FIG.

5A and 5B show side views of an example of an ECL structure in which wavelength variability is caused by heat based on a PLC.

6A and 6B show side views of an example of ONT-TOSA that is wavelength variable by heat based on vertically coupled ECLs.

7A and 7B show respective side views of another example of ONT-TOSA that is wavelength variable by heat based on vertically coupled ECLs.

8A and 8B show top and side views, respectively, of an example of an OLT-TOSA that is wavelength-variable by heat based on vertically coupled ECLs.

9A and 9B show side and top views, respectively, of another example of an OLT-TOSA that is wavelength variable by heat based on vertically coupled ECLs.

10 is a block diagram showing a logical structure of a WDM-PON according to another embodiment of the present invention.

The present invention relates to a WDM-PON system, and more particularly to a WDM-PON system having an optical wavelength alignment function for maintaining the optical communication path according to the temperature change.

The essential consideration for WDM-PON for subscriber network is to change the optical characteristics of each module included in the network according to the temperature change.

In particular, the subscriber network is exposed to the change in the ambient temperature of the optical devices on the subscriber side, and the ambient temperature is different depending on the location where the equipment is installed, there is a problem that smooth optical communication is not possible without considering this. On the other hand, despite the change in the ambient temperature in the WDM-PON system has been proposed a way to overcome this economically.

In other words, when the conventional WDM-PON system is applied to a real environment, it is necessary to present a WDM-PON system that maintains a stable optical communication path despite a change in ambient temperature. There is a need.

An object of the present invention is to propose a WDM-PON system having an optical wavelength alignment function for maintaining a stable optical communication path despite a change in ambient temperature.

A specific technical problem for this is to form a wavelength-variable LD so that the light sources of the OLT optical transmitter can vary the output light wavelength to accommodate the wavelength change according to the ambient temperature change of the subscriber side WDM MUX / DMX. Each of the optical transmitter and the optical receiver of the OLT forms a wavelength tunable OPM-LD for the purpose of detecting the wavelength change according to the ambient temperature change of the WDM MUX / DMX on the subscriber side and responding appropriately. In addition, the output light wavelength of the ONT optical transmitter is to match the wavelength of the WDM MUX / DMX of the subscriber side changed according to the ambient temperature change without additional light source.

WDM-PON system having an optical wavelength alignment function according to the present invention for achieving the above technical problem, the first wavelength control circuit for aligning the OLT-LD array for generating the optical wavelength for data transmission and the wavelength of the downlink path for the optical wavelength change The optical transmitter comprises a light receiver comprising a light transmitter, a photodetector (PD) array, and a second wavelength control circuit for aligning wavelengths of an uplink path for a change in optical wavelength. The optical transmitter includes a plurality of optical wavelengths output from the OLT-LD array. An optical line terminal (OLT) having a first wavelength multiplexer (WDM MUX) for multiplexing and having a first wavelength divider (WDM DMX) for separating and receiving the multiplexed optical wavelengths for each wavelength; The optical receiver and the wavelength variable waveguide Bragg grating (WBG) for receiving the downlink data transmission optical wavelength transmitted from the optical transmitter of the OLT are formed and applied to the waveguide Bragg grid according to the downlink data transmission optical wavelength input from the OLT. A plurality of optical network terminals (ONTs) comprising an optical transmitter configured of an external resonant laser (ECL) to control the temperature at which the light is changed; Located in the MDF (Main Distribution Frame) near the plurality of ONTs, the multiplexed optical wavelengths transmitted through the optical fiber from the first wavelength multiplexer of the OLT are divided by wavelength, and each optical wavelength is connected to a corresponding ONT among the ONTs. A second wavelength divider (WDM DMX) having a first OPM-RM port for reflecting an optical wavelength transmitted from one wavelength control circuit; And multiplexing a plurality of optical wavelengths located in a main distribution frame (MDF) near the plurality of ONTs and outputting from the optical transmitter of the ONT, and transmitting the multiplexed optical wavelengths to a first wavelength divider of the OLT through an optical fiber. And a second OPM-RM port for reflecting the OPM-LD output optical wavelength and a WDM-RM port for reflecting the optical signal to the optical transmitter of the ONT depending on the degree of inconsistency in the passband of the optical wavelength output from the optical transmitter of the ONT. And a second wavelength multiplexer (WDM MUX).

In addition, the WDM-PON system having an optical wavelength alignment function according to the present invention for achieving the above technical problem, WDM-PON system having an optical wavelength alignment function, a fixed substrate; Passive waveguide region in front of the active waveguide region by using an active waveguide region for generating light and a directional coupling principle for vertically coupling the light generated in the active waveguide region to another waveguide. a semiconductor chip having a passive region; A PLC waveguide formed on the fixed substrate, having a PLC platform formed at one end thereof to surface-bond the semiconductor chip by a manual alignment method, and having a waveguide bragg grating (WBG) formed at a predetermined point; A directional coupler for transmitting optical power by bringing the passive waveguide region into close proximity to the PLC waveguide; A heater electrode formed on the top of the WBG to control the temperature of the WBG; And an optical fiber formed on the silicon substrate at the other end of the PLC waveguide.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

1A and 1B are block diagrams of a WDM-PON having an optical wavelength alignment function according to temperature change according to an embodiment of the present invention.

1A and 1B, loop A, loop B, and loop C for matching the optical wavelengths of the constituent modules whose optical wavelengths change with temperature change in the WDM-PON structure according to an embodiment of the present invention are shown. Indicates.

FIG. 1A illustrates a downlink transmission path from a central office (CO) to a subscriber. FIG. 1A shows an OLT optical transmission module 100 consisting of an OLT-LD 102 for data transmission and an OPM-LD 104 added for the purpose of wavelength alignment of the downlink path to temperature changes, located within the OLT. It can be seen that the OLT-WMUX 110, the RN-WDMX 120 located near the subscriber side, and the ONT-PD 130, which is a subscriber optical reception module.

The portion where the temperature change occurs in the downlink transmission path and the central optical wavelength changes are three parts of the OLT optical transmission module 100, the OLT-WMUX 110, and the RN-WDMX 120. Here, the RN-WDMX 120 is most severely exposed to changes in the ambient temperature due to the characteristics of the PON, and no electrical device for temperature control is provided. Accordingly, the wavelength change of the RN-WDMX 120 becomes a reference point, and the OLT optical transmission module 100 and the OLT-WMUX 110 respectively adjust their wavelengths to the wavelength of the RN-WDMX 120.

1B illustrates an uplink transmission path from a subscriber to a central office (CO). The uplink transmission path from the subscriber to the CO is the subscriber optical transmission module ONT-LD 150, the RN-WMUX 160 located near the subscriber side, the OLT-WDMX 170 located in the OLT, and the upstream temperature change. It consists of an OPM-LD 180 added for the purpose of wavelength alignment of the transmission path.

In the uplink, the wavelength changes according to the temperature change in four parts of the subscriber optical transmission module ONT-LD (150), RN-WMUX (160), OLT-WDMX (170) and OPM-LD (180). to be. Here, as in the case of the downlink transmission path, the RN-WMUX 160 is most severely exposed to changes in the ambient temperature due to the characteristics of the PON, and no electrical device for temperature control is provided. Accordingly, the wavelength change of the RN-WMUX 160 is a reference point, and the ONT-LD 150 detects the wavelength change of the RN-WMUX 160 to adjust the wavelength. The OLT-WDMX 170 and the OPM-LD 180 align their wavelengths to the changed wavelengths of the RN-WMUX 160 independently of the ONT-LD 150.

Wavelength alignment of the downlink path is performed by loop A. That is, the wavelength change of the wavelength is transmitted from the OPM-LD 104 to the RN-WDMX 120 and the center wavelength change of the RN-WDMX 120 is reflected by the intensity of the optical signal reflected back from the RN-WDMX 120. It detects and aligns the wavelength accordingly.

On the other hand, wavelength alignment of uplink paths is performed independently by loop B and loop C, respectively. That is, the wavelength alignment of the ONT-LD 150 is performed by the loop C. The optical wavelength for data transmission output from the ONT-LD 150 is reflected from the RN-WMUX 160 to return the RN from the intensity of the optical signal. Detects the misalignment of the WMUX 160 and thus aligns the wavelength of the ONT-LD 150 with the wavelength of the RN-WMUX 160. In addition, wavelength alignment in the OLT-WDMX 170 and the OPM-LD 180 is performed by loop B. FIG. That is, the wavelength of the RN-WMUX 160 is detected by the intensity of the optical signal reflected from the RN-WMUX 160 by transmitting the wavelength change measurement light from the OPM-LD 180 and correspondingly the wavelength is measured. Will be aligned.

2 is a block diagram showing a logical structure of a WDM-PON according to an embodiment of the present invention.

Looking at the basic operation of the WDM-PON system in Figure 2 as follows. The optical line terminal (OLT) 200 located in the central office (CO) includes an optical transmitter 210 and a photo detector (PD) in the form of an external cavity laser (ECL) array. It consists of an optical receiver 220 in the form of an array.

The optical network terminal (ONT) 260 is an optical transmitting unit composed of an external resonant laser (hereinafter, referred to as 'ECL') based on a broadband waveguide Bragg-grating (WBG). 285) and an optical receiver (ONT-PD) 270.

The optical transmitter 210 of the OLT 200 includes an OLT-WDM multiplexer (WDM MUX) 204 for multiplexing a plurality of optical wavelengths output from the ECL array, and the OLT 200 The optical receiver 220 includes an OLT-WDMX (OLT-WDMX) 206 for separating and receiving the multiplexed optical wavelengths inputted from the plurality of ONTs 260 by wavelength. .

The multiplexed optical wavelengths output from the optical transmitter 210 of the OLT 200 are transmitted through the optical path and divided by wavelength by the RN-WDMX 240 located near the subscriber, and each optical wavelength is connected to the corresponding ONT 260. do. The different optical wavelengths output from the ONTs 260 are multiplexed in the OLT-WMUX 250 near the subscriber and connected to the optical receiver 220 of the OLT 200 through a light path.

The ONT 260 has an ECL in the form of a separate element composed of a Fabry-Perot laser diode (FP-LD) and a WBG in the same manner as the OLT 200. As such, the biggest feature of the ECL is that the WBG reflection band center wavelength is varied in a wide light wavelength range by a heater, so that the light wavelength can be produced regardless of a specific light wavelength.

Referring to FIG. 2, the optical transmitter 210 of the OLT 200 basically includes an OLT-LD array 202 that transmits light at a frequency interval recommended by the ITU-T. The multi-wavelength optical signals at the output terminal of the OLT-LD array 202 are wavelength-multiplexed by the OLT-WMUX 204 and output to the downlink path. The OLT-WMUX 204 receives n data transmission LD wavelengths from the OLT-LD array 202 and multiplexes the output optical wavelengths from the OPM-LD 212 to have a (n + 1) × 1 form. An optical circulator 214 is positioned between the OPM-LD 212 and the OLT-WMUX 204. The optical circulator 214 outputs the OPM light that is output from the OPM-LD 212 and reflected from the reflection mirror (OPM-RM) 242 of the RN-WDMX 240 to the PD2 216. The Wavelength Control Circuit (WCC) 218 receives the electrical outputs of the monitor PD and the PD2 216 existing in the OPM-LD 212, and the wavelength of the OLT-WMUX 204 and the OLT-LD array (WCC). It adjusts the wavelength of 202 and the wavelength of the OPM-LD 212, and also monitors the connection of the downlink. Here, reference numeral 211 denotes a wavelength control circuit.

The optical receiver 220 of the OLT 200 includes an n-number PD array 208 and an OLT-WDMX 206. The OLT-WDMX 206 takes the form of (n + 1) × 1 to separate the n multiplexed data wavelengths for transmission and send the light output from the OPM-LD 222 back to the subscriber. An optical circulator 224 is positioned between the OPM-LD 222 and the OLT-WDMX 206. The optical circulator 224 transmits the OPM light output from the OPM-LD 222 and reflected from the OPM-RM 252 of the RN-WMUX 250 to the PD2 226. The WCC 228 receives the electrical outputs of the mPD and PD2 226 present in the OPM-LD 222, controls the wavelength of the OLT-WDMX 206 and the wavelength of the OPM-LD 222 and also the uplink Monitor the connection status. Here, reference numeral 221 denotes a wavelength control circuit.

The RN-WDMX 240 receives the multiplexed optical wavelengths input from the optical transmitter 210 of the OLT 200 and separates n output ports and transmits them to the ONT 260 and the optical transmitter 210 of the OLT 200. Since it includes a port connecting the OPM-RM (242) reflecting the optical wavelength input from the OPM-LD (212) has a (n + 1) x 1 form.

Different optical wavelengths carrying uplink data output from subscriber ONT 260 are multiplexed in RN-WMUX 250 and directed to OLT-WDMX 206 via the uplink. An optical circulator 292 is connected between the ONT-LD 285 and the RN-WMUX 250. The optical circulator 292 transmits the light output from the ONT-LD 285 and reflected from the WDM-RM 254 of the RN-WMUX 250 to the PD2 294. The WCC 296 receives the electrical outputs of the mPD and PD2 294 included in the ONT-LD 285 to control the optical wavelength of the ONT-LD 285.

The RN-WMUX 250 receives n input ports for receiving n data transmission ONT-LD 285 output wavelengths and an OPM-LD that reflects the OPM-LD output wavelengths emitted from the optical receiver 220 of the OLT 200. RM 252 and WDM-RM 254 that reflects optical power toward the ONT transmitter in proportion to the degree of the light wavelengths output from the ONT-LD 285 and the wavelength of the RN-WMUX 250 inconsistent ( n + 1) x2.

The optical wavelengths are arranged throughout the network in response to changes in ambient temperature.

1) In the PON type network, it may be assumed that the RN-WMUX 250 is exposed to a change in ambient temperature. Since the wavelength of the RN-WMUX 250 changes according to the ambient temperature, when one ONT 260 attempts to communicate, the optical wavelength output from the ONT-LD 285 is generally the center wavelength of the RN-WMUX 250. The intensity of reflected light is changed according to the degree of mismatch in the WDM-RM 254 of the RN-WMUX 250. The reflected light reflected from the WDM-RM 254 and incident on the optical transmitter 280 of the ONT 260 may be regarded as an upward optical wavelength signal output from the ONT 260 which has attempted communication. The reason why it is regarded as an upward optical wavelength signal is that the plurality of ONTs 260 are extremely unlikely to initiate communication at the same time accurately, and the ONTs 260 in the communication state are each ONT-LD at the wavelength of the RN-WMUX 250. This is because the output light wavelengths of (285) are already aligned. Accordingly, the WCC 296 of the ONT 260 which has just started communication compares the reflected optical power intensity inputted to the PD2 294 with the transmitted optical power inputted through the mPD included in the ONT-LD 285. The optical wavelength is aligned to match the -LD 285 wavelength to the RN-WMUX 250 wavelength.

2) The WDM-RM 254 of the RN-WMUX 250 turns on the optical power in proportion to the degree of mismatch with the wavelength of the RN-WMUX 250 for each of the wavelengths incident to the n input ports. Reflected toward the light transmitting unit 280 of 260. The RN-WMUX 250 is formed such that the OPM-LD optical signal from the OLT 200 is passed through the n data input ports toward the optical transmitter 280 of the ONT 260.

3) The OPM-LD 212 in the optical transmitter 210 of the OLT 200 sends down the OPM light through the OLT-WMUX 204. The OPM light is reflected by the OPM-RM 242 attached to the ONT 260 side of the RN-WDMX 240 and returned to the optical transmitter 210 of the OLT 200. At this time, the amount of reflection in the OPM-RM 242 is determined according to the degree of inconsistency between the wavelength of the RN-WDMX 240 and the wavelength of the OPM-LD 212 changed according to the ambient temperature, and the reflected light is transmitted through the optical circulator 214. Incident at 216. The WCC 218 compares the mPD output signal in the OPM-LD 212 with the output signal of the PD2 216 to compare the wavelength of the OLT-WMUX 204, the wavelength of the OLT-LD array 202, and the OPM-LD ( The wavelength of 212 is controlled to align with the wavelength of the RN-WDMX 240.

The WCC 218 determines and manages the downlink fiber state based on the output signals received from the mPD and PD2 216 of the OPM-LD 212.

4) Similarly, the OPM-LD 222 at the light receiving unit 220 of the OLT 200 sends the light for the OPM to the RN-WMUX 250 through the OLT-WDMX 206 and the uplink. The OPM light is reflected by the OPM-RM 252 attached to the ONT 260 side of the RN-WMUX 250 and returned to the light receiving unit 220 of the OLT 200. At this time, the amount of reflection in the OPM-RM 252 is determined according to the degree of inconsistency between the wavelength of the RN-WMUX 250 changed according to the ambient temperature and the wavelength of the OPM-LD 222, and the reflected light is transmitted through the light circulator 224. Incident at 226. The WCC 228 compares the mPD output signal in the OPM-LD 222 with the output signal of the PD2 226 so that the wavelength of the OLT-WDMX 206 and the wavelength of the OPM-LD 222 are RN-WMUX 250. Control to be aligned to the wavelength of.

The WCC 228 determines and manages an uplink fiber state based on the output signals received from the mPD and PD2 226 of the OPM-LD 222.

3 is a plan view showing in detail the structure of the RN-WDMX 240 of FIG. RN-WDMX 240 is a 1X (N + 1) WDM DMX.

이라고 가정한다. 그리고, RN-WDMX(340)의

신호를 출력하는 출력포트에는 OPM- RM(370)이 존재하여

파장을 반사하게 된다. OPM-RM(370)은 해당 출력포트 끝단에 dielectric multi-layer coating 또는 metal coating등을 이용하여 mirror를 구성할 수 있다. 또는, Bragg-reflector, bulk mirror등과 같은 개별 소자를 광접속하여 구성할 수도 있다. Referring to FIG. 3, the wavelength transmitted from the OPM-LD 212 of the OLT 200 is

Assume that And the RN-WDMX 340

OPM-RM (370) is present in the output port for outputting signals

Reflect the wavelength. The OPM-RM 370 may configure a mirror by using a dielectric multi-layer coating or a metal coating at the end of the corresponding output port. Alternatively, individual devices such as Bragg-reflectors and bulk mirrors may be optically connected.

The structure of the RN-WDMX 340 may be an arrayed-waveguide grating, a WDM filter, or the like.

4 is a plan view showing in detail the structure of the RN-WMUX 250 of FIG. RN-WMUX 250 is a 2X (N + 1) WDM MUX.

, ONT(260)에서 송출하는 파장은

,

,...,

이라고 가정한다. Referring to Figure 4, the wavelength transmitted by the OPM-LD 212 of the OLT 200 is

, The wavelength transmitted from the ONT 260 is

,

, ...,

Assume that

신호를 출력하는 해당 포트(42n+1)의 끝에는 OPM-RM(410)이 존재하여

신호를 반사하게 된다. 그리고, 파장결합하여 출력되는 optical fiber 2(452)의 끝에는 WDM-RM(470)이 존재하여

,

,...,

광신호들을 모두 반사한다. 파장결합하여 출력되는 광섬유 1(optical fiber 1)(450)은 상향 통신로를 형성하는 광섬유이다. 광손실을 고려하여 RN-WMUX(250)의 설계시 두 광섬유간 회절차수 차이를 적어도 1이상 두어서 광섬유 2(optical fiber 2)(452) 로는 최소한의 광신호만 전달되도록 한다.Of RN-WMUX (430)

OPM-RM (410) is present at the end of the corresponding port (42n + 1) that outputs a signal

It will reflect the signal. The WDM-RM 470 is present at the end of the optical fiber 2 452 that is output by combining wavelengths.

,

, ...,

Reflects all optical signals Optical fiber 1 450 that is output by combining wavelengths is an optical fiber forming an uplink communication path. In consideration of the optical loss, in designing the RN-WMUX 250, at least one difference in diffraction orders between two optical fibers is provided so that only a minimum optical signal is transmitted to the optical fiber 2 452.

Here, the reflection mirror elements such as the OPM-RM 410 and the WDM-RM 470 may form a mirror by using a dielectric multi-layer coating or a metal coating on the end of the corresponding optical fiber. Alternatively, individual devices such as Bragg-reflectors and bulk mirrors can be optically connected.

The structure of the RN-WMUX 430 may be an arrayed-waveguide grating, a WDM filter, or the like.

5A and 5B show side views of an example of an ECL structure in which wavelength variability is caused by heat based on a PLC.

Referring to FIG. 5A, an active waveguide region 524 of an InP chip that generates light (which is viewed as an InP chip in one embodiment of the present invention, but may be broadly formed as a semiconductor chip) 520. Unlike the conventional butt coupling method in which the waveguide Bragg Grating (hereinafter referred to as 'WBG') 555 is coupled in a straight line, the active waveguide region 524 and the WBG 555 exist on different waveguides, respectively. It has a vertically coupled structure. FIG. 5A shows an ECL structure characterized by varying the temperature of the WBG 555 so that the output light wavelength can be varied by the thermo-optic effect.

InP chip 520 consists of an active waveguide region 524 that generates light and a passive region 522 in front of the active waveguide region 524 to couple the generated light vertically to another waveguide. do. As the waveguide material of the InP waveguide (in the embodiment of the present invention, the InP waveguide may be broadly formed as a semiconductor waveguide) 526, a semiconductor (InP-based), a polymer, a nitride, and a silica may be used. The waveguide structure may be a channel waveguide, a ridge-loaded waveguide, a rib waveguide, or the like.

The InP chip 520 having such a configuration is formed on an InP substrate and is surface-mounted to a PLC platform using a low-cost passive alignment method such as flip-chip bonding.

InP waveguide 526 has a structure in which the waveguide size decreases as it moves away from the active waveguide region 524 to efficiently optically couple light generated in the active waveguide region 524 with the PLC waveguide 560. waveguide 528 has a structure. The passive waveguide region 522 also transmits most of the light to or below the PLC waveguide 560 before the light generated from the active waveguide region 524 reaches the end of the InP waveguide 526. It consists of a structure that is lost. This is to prevent the light emitted from the active waveguide region 524 from being reflected at the end of the InP waveguide 526 and re-entered into the active waveguide region 524.

PLC waveguide 550 also has a down-tapered PLC waveguide 562 structure that can increase the magnitude of propagating light. This structure prevents light reflected from the Waveguide Bragg Grating (hereinafter referred to as 'WBG') 555 from being reflected at the opposite end of the PLC waveguide 560. The proper use of the down-tapered PLC waveguide 562 structure can satisfy the phase-matching condition between the two waveguides, thereby increasing the optical coupling efficiency between the two waveguides.

The refractive index of the InP waveguide 526 is up to twice as large as that of the PLC waveguide 560 using silica or polymer material. When the difference in refractive index is large, a directional coupler that transmits optical power by approaching the waveguide has little light transmission effect because the phase-matching condition cannot be satisfied. As a method for solving the problem of low light transmission effect, as shown in FIG. 5A, a lattice is counted on the junction between the InP waveguide 526 and the PLC waveguide 560 to satisfy the phase matching condition between two waveguides. Leaky-mode grating-assisted directional coupler (LM-GADC) has been proposed.

A WBG 555 is formed on the PLC waveguide 560 and a heater terminal 550 is mounted on the top of the WBG 555 to control the temperature of the WBG 555. The wavelength variable WBG 555 is formed by temperature control through the heater electrode 550.

Issues relating to FIG. 5A are described in US Pat. No. 6,236,773, entitled Single wavelength semiconductor laser with grating-assisted dielectric waveguide coupler, Applicant-Texas Instruments Incorporated.

Referring to FIG. 5B, a method of etching a portion of the InP chip 520 and forming a waveguide using a dielectric material (dielectric medium) 525 having a refractive index similar to that of a PLC (ESMC: etched surface -mount coupler). The rest of the description will be described with reference to FIG. 5A.

6A and 6B show respective side views of one example of ONT-TOSA that is wavelength variable by heat based on vertically coupled ECLs. FIG. 6A uses the LM-GADC method described with reference to FIG. 5A, and FIG. 6B uses the ESMC method described with reference to FIG. 5B.

6A and 6B, a conventional butt coupling in which an active waveguide region 624 of a light generating InP chip 620 and a Waveguide Bragg Grating (hereinafter referred to as 'WBG') 655 are linearly coupled. Unlike the scheme, the active waveguide region 624 and the WBG 655 exist on different waveguides, respectively, and have a vertically coupled structure between the different waveguides. By having such a structure that is optically stacked in the vertical direction it is possible to reduce the difficulty of manufacturing and to improve the simplification of the process.

In proximity to the InP chip 620, an mPD 610 is mounted to monitor the magnitude of light generated in the active waveguide region 624. A WBG 655 is formed on the PLC waveguide 660 and a heater terminal 650 is mounted on the top of the WBG 655 to control the temperature of the WBG 655. The wavelength variable WBG 655 is formed by temperature control through the heater terminal 650. The PLC waveguide 660 in the vicinity of the optical fiber 680 is composed of a spot-size converter 670 to enlarge the beam in the PLC waveguide 660 to increase the optical coupling efficiency with the optical fiber. . The optical fiber 680 is manually aligned and mounted using the V-groove 685 formed on the PLC to simplify the alignment process.

WBG 655 fabricated using a waveguide made of silica material may have a wavelength variation of about 2 nm due to a temperature change of 200 degrees Celsius in a light wavelength variable range. However, there is a problem in that the economical efficiency is inferior because the number of channels is too small to be used as the WDM variable wavelength light source (for example, two channels are generated at intervals of 200 GHz). In contrast, the polymer-based WBG 655 has a variable wavelength range of up to about 30 nm with a temperature variation of 200 degrees Celsius, which is economically effective in terms of channel number (for example, at 200 GHz intervals). 18 channels can be created).

Parts not described in FIGS. 6A and 6B will be referred to FIGS. 5A and 5B.

7A and 7B show respective side views of another example of ONT-TOSA that is wavelength variable by heat based on vertically coupled ECLs.

Referring to FIG. 7A, the basic structure is the same as that described in FIG. 6B, but the difference is that a phase adjusting region 727 is inserted for fine tuning and stable operation of the oscillating wavelength. FIG. 7A shows a side view of a phase control region 727 integrated in the InP chip 720. Here, phase control is performed by controlling the amount of current injected into the phase adjusting region 727.

Referring to FIG. 7B, the basic structure is the same as that described in FIG. 6B, but a phase control unit 790 is present in the PLC waveguide 760 for fine tuning and stable operation of the oscillated wavelength. Is that. Here, in the phase control, the electro-optic effect or the thermo-optic effect of the waveguide is used.

Parts not described in FIGS. 7A and 7B will be described with reference to FIGS. 5A, 5B, and 6B.

8A and 8B show top and side views, respectively, of an example of an ONT-TOSA that is wavelength variable by heat based on vertically coupled ECLs.

8A and 8B, the FP-LD array 820 ′ that generates light forms an ECL one to one with a WBG array having a reflection band at a frequency interval recommended by the ITU-T. In each ECL, the reflection band center wavelength of the corresponding WBG is set so that the WDM optical signal of a predetermined frequency interval can be transmitted.

The WBG array allows the wavelength of each WBG to be independently changed by the thermo-optic effect, thereby greatly improving the yield of the waveguide Bragg Grating process error and allowing the wavelength to be aligned with the change of the ambient temperature.

The multi-wavelength optical signals at the output end of the ECL array are wavelength multiplexed by the WDM MUX 895 monolithicly integrated into one PLC chip and finally output. By integrating the ECL array and the WDM MUX 895 on one PLC, the fiber pigtail process of the optical transmission module is simplified to one. The WDM MUX 895 may be integrated with an arrayed-waveguide grating (AWG) or a WDM filter.

In the semiconductor chip for generating light, FIG. 8A or FIG. 8B is manufactured in the form of an FP-LD array 820 '. Here, the method of using individual FP-LD chips for each ECL has a long process time during manual alignment using the flip-chip bonding method, and there is a problem in that the bonded chips are misaligned when bonding other chips. In FIG. 8A or 8B, the above problems are solved by using the FP-LD array 820 ′. Monitor PD (mPD) is also manufactured in the form of mPD array (810 ') to monitor the optical output power of each ECL module.

9A and 9B show side and top views, respectively, of another example of ONT-TOSA that is wavelength-variable by heat based on vertically coupled ECLs.

The basic structure of FIG. 9A is the same as that of FIG. 8A, but a phase adjusting portion for fine tuning of wavelength and stable operation is added. 9A shows a case where the phase adjusting portion is integrated in the InP chip. Phase control is performed by controlling the amount of current injected into the area. 9B shows a case where the phase control portion is inserted into the PLC waveguide. Phase control is performed using the electro-optic or thermo-optic effects of the waveguide.

9A and 9B, the basic structure is the same as that described in FIGS. 8A and 8B, but different portions are phase control regions 927 for fine tuning and stable operation of the oscillated wavelength. Is inserted. 9A illustrates a side view of the phase adjuster 927 integrated with the InP chip 920. Here, phase control is performed by controlling the amount of current injected into the phase adjuster 927.

10 is a block diagram showing a logical structure of a WDM-PON according to another embodiment of the present invention.

Referring to FIG. 10, optical sub-assemblies (OSAs) constituting the proposed WDM-PON are displayed. ONT-TOSA (Transmitter OSA) 1085 for subscriber ONT, OLT-TOSA 1011 for OLT transmitter, OLT-ROSA (Receiver OSA) 1021 for OLT receiver, and RN- located near subscriber's residence Four types of OSAs, such as WMUX / WDMX 1030, may be configured.

When these four types of OSAs are each manufactured by PLC, the optical transmission of the proposed WDM-PON system is composed of four PLC chips, which has advantages in terms of volume and mass production. 2 differs from the OLT-LD array 202 in FIG. 2 as an OLT-ECL array 1012 in FIG. 10, and the ONT-LD 285 in FIG. 2 is an ECL 1085 in FIG. 10. It is made up of. In addition, the OPM-LD for generating the optical wavelength for alignment in the optical transmitter and the optical receiver of the OLT in FIG. 2 is composed of an OPM-ECL in FIG. A portion not described in FIG. 10 will be referred to FIG. 2.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The present invention relates to a WDM-PON having an optical wavelength alignment function for maintaining an optical communication path against temperature changes, and has the following effects.

When the WDM-PON optical distribution network is applied to a real environment, a function of maintaining a stable optical communication path is required in spite of a change in ambient temperature. In the present invention, a WDM-PON system having an optical wavelength alignment function capable of realizing optical wavelength alignment is cost-effective. Can be provided.

Claims (39)

An optical transmitter and photodetector (PD) array and an uplink path for an optical wavelength change comprising an OLT-LD array for generating an optical wavelength for data transmission and a first wavelength control circuit for aligning wavelengths of the downward path for optical wavelength changes. And a light receiver comprising a second wavelength control circuit for aligning the signal. The optical transmitter has a first wavelength multiplexer (WDM MUX) for multiplexing a plurality of optical wavelengths output from the OLT-LD array, and the optical receiver is multiplexed. An optical line terminal (OLT) having a first wavelength divider (WDM DMX) for separating the received optical wavelengths by wavelength; The optical receiver and the wavelength variable waveguide Bragg grating (WBG) for receiving the downlink data transmission optical wavelength transmitted from the optical transmitter of the OLT are formed and applied to the waveguide Bragg grid according to the downlink data transmission optical wavelength input from the OLT. A plurality of optical network terminals (ONTs) comprising an optical transmitter configured of an external resonant laser (ECL) to control the temperature at which the light is changed; Located in the MDF (Main Distribution Frame) near the plurality of ONTs, the multiplexed optical wavelengths transmitted through the optical fiber from the first wavelength multiplexer of the OLT are divided by wavelength, and each optical wavelength is connected to a corresponding ONT among the ONTs. A second wavelength divider (WDM DMX) having a first OPM-RM port for reflecting an optical wavelength transmitted from one wavelength control circuit; And Located in the MDF (Main Distribution Frame) near the plurality of ONTs and multiplexing a plurality of optical wavelengths outputted from the optical transmitter of the ONT, the plurality of optical wavelengths are transmitted to the first wavelength divider of the OLT through an optical fiber, and the OPM from the second wavelength control circuit. A second OPM-RM port for reflecting the LD output optical wavelength and a WDM-RM port for reflecting the optical signal to the optical transmitter of the ONT depending on the degree of inconsistency in the passband of the optical wavelength output from the optical transmitter of the ONT; WDM-PON system having a wavelength alignment function, characterized in that it comprises a two wavelength multiplexer (WDM MUX). The optical transmitter of claim 1, wherein the optical transmitter of the OLT An OLT-LD array unit generating the downlink data wavelength; A first OPM-LD outputting an alignment optical wavelength for aligning an optical wavelength for downlink data transmission transmitted from the OLT to the ONT; A first wavelength multiplexer which multiplexes the downlink data transmission wavelength and the alignment wavelength; The first optical circulator for transmitting the optical wavelength for alignment output from the first OPM-LD to a first wavelength multiplexer, and the optical wavelength reflected from the first OPM-RM port of the second wavelength divider to the first PD2 below. (optical circulator); A first PD2 converting the reflected light into an electrical signal; And The first wavelength multiplexer, the OLT-LD array unit, and the first OPM- receive the output optical power information of the first OPM-LD and the output signal of the first PD2 through a first monitoring photodetector (mPD). A WDM-PON system having an optical wavelength alignment function comprising a first WCC for controlling the wavelength of the LD. The method of claim 2, wherein the second wavelength divider According to the degree of inconsistency between the alignment optical wavelength output from the first OPM-LD and the center wavelength of the second wavelength divider, the alignment optical wavelength output from the first OPM-LD is the first OPM-RM of the second wavelength divider. WDM-PON system having an optical wavelength alignment function, characterized in that the intensity of the optical wavelength reflected from the port is incident to the first PD2. The method of claim 2, wherein the first WCC is Transmission optical power information of the first OPM-LD input through a monitoring photodetector (mPD) monitoring the alignment optical wavelength output from the first OPM-LD and an optical signal converted into an electrical signal in the first PD2 WDM-PON system having an optical wavelength alignment function, characterized in that receiving the input. The optical receiver of claim 1, wherein the optical receiver of the OLT is provided. An OLT-PD array unit for detecting an uplink optical wavelength for multiplexed data transmission output from the ONT; A second OPM-LD for outputting an optical wavelength for aligning an upward optical wavelength for multiplexed data transmission transmitted from the ONT to the OLT; A first wavelength divider for wavelength separation of the multiplexed data transmission upward optical wavelength and the alignment optical wavelength transmitted from the ONT to the OLT; A second optical circulator for transferring the light output from the second OPM-LD to the first wavelength divider, and for transferring the light reflected from the second OPM-RM port of the second wavelength multiplexer to a second PD2; (optical circulator); A second PD2 for converting the reflected light into an electrical signal; And The first wavelength divider, the OLT-PD array unit and the second OPM- receive the optical power information transmitted from the second OPM-LD and the output signal of the second PD2 through a second monitoring photodetector (mPD). WDM-PON system having a wavelength alignment function, characterized in that it comprises a second WCC for controlling the wavelength of the LD. The method of claim 5, wherein the second wavelength multiplexer The output light wavelength of the second OPM-LD is reflected by the second OPM-RM port of the second wavelength divider according to the degree of mismatch between the alignment wavelength output from the second OPM-LD and the center wavelength of the second wavelength splitter. And the intensity of the optical wavelength incident on the second PD2 is changed. The method of claim 5, wherein the second WCC is The optical power information of the second OPM-LD input through a monitoring photodetector (mPD) for monitoring an alignment optical wavelength output from the second OPM-LD and an optical signal converted into an electrical signal from the second PD2 WDM-PON system having an optical wavelength alignment function, characterized in that the input. The method of claim 1, wherein the second wavelength divider A first OPM-RM port for separating the n downlink data transmission optical wavelengths transmitted from the first wavelength divider and reflecting the OPM-LD optical wavelengths transmitted from the first wavelength control circuit to the OLT (n +1) WDM-PON system having a wavelength alignment function, characterized in that x 1 structure. The method of claim 8, When the optical wavelength for alignment output from the first OPM-LD transmitted from the first wavelength control circuit coincides with the center wavelength of the second wavelength divider, the light of the OLT at the first OPM-RM port of the second wavelength divider WDM-PON system with a wavelength alignment function, characterized in that there is no optical wavelength reflected back to the transmitter. The method of claim 8, The optical wavelength reflected by the optical transmitter of the OLT increases proportionally according to the degree of mismatch between the alignment optical wavelength output from the first OPM-LD transmitted from the first wavelength control circuit and the center wavelength of the second wavelength divider. WDM-PON system with optical wavelength alignment function. The method of claim 8, The n ports for data and the first OPM-RM ports are designed such that the output light of the first OPM-LD transmitted from the first wavelength control circuit is not transmitted to the ONT in any temperature change interval considered. WDM-PON system with optical wavelength alignment function. The method of claim 1, The second wavelength multiplexer includes: a second OPM-RM port for multiplexing n data transmission optical wavelengths transmitted from the optical transmitter of the ONT and reflecting OPM-LD output optical wavelengths transmitted from the second wavelength control circuit; And (n + 1) having a WDM-RM port for reflecting optical power to the optical transmitter of the ONT according to the degree of mismatch when the optical wavelength transmitted from the optical transmitter of the ONT is inconsistent with the passband of the second wavelength multiplexer. WDM-PON system having a wavelength alignment function, characterized in that the x 2 structure. The method of claim 12, When the n wavelengths of data transmission transmitted from the optical transmitter of the ONT coincide with the center wavelength of the second wavelength multiplexer, the optical wavelength reflected from the WDM-RM port of the second wavelength multiplexer to the optical transmitter of the ONT is WDM-PON system with an optical wavelength alignment function characterized in that there is no. The method of claim 12, WDM having an optical wavelength alignment function characterized in that the optical wavelength reflected by the optical transmitter of the ONT increases in proportion to the mismatch of the n wavelengths of data transmission transmitted from the optical transmitter of the ONT and the center wavelength of the second wavelength divider. -PON system. The method of claim 12, The alignment optical wavelengths outputted from the second OPM-LD transmitted from the second wavelength control circuit in any temperature change interval considered are not provided by the n ports for data and the second OPM-RM ports so that they are not transmitted to the ONT. WDM-PON system having a wavelength alignment function, characterized in that designed. The optical transmitter of claim 1, wherein ONT-LD for generating the optical wavelength for the uplink data transmission; A third optical circulator for transmitting the light output from the ONT-LD to the second wavelength multiplexer and transferring the light reflected from the WDM-RM port of the second wavelength multiplexer to a third PD2 below; A third PD2 for converting the reflected light into an electrical signal; And And a third WCC for controlling the wavelength of the ONT-LD by receiving the output optical power information of the ONT-LD and the output signal of the third PD2 through a monitoring photodetector (mPD). WDM-PON system with. The method of claim 16, The optical wavelength reflected by the ONT-LD is changed according to the degree of mismatch between the output light wavelength output from the ONT-LD and the center wavelength of the second wavelength multiplexer WDM-PON system having an optical wavelength alignment function. The method of claim 16, The third WCC is arranged to align the wavelength of the ONT-LD with the optical wavelength of the second wavelength divider through the transmission optical power information of the ONT-LD and the output signal of the third PD2. WDM-PON system with. In the WDM-PON system having a wavelength alignment function, A stationary substrate; Passive waveguide region in front of the active waveguide region by using an active waveguide region for generating light and a directional coupling principle for vertically coupling the light generated in the active waveguide region to another waveguide. a semiconductor chip having a passive region; A PLC waveguide formed on the fixed substrate, having a PLC platform formed at one end thereof to surface-bond the semiconductor chip by a manual alignment method, and having a waveguide bragg grating (WBG) formed at a predetermined point; A directional coupler for transmitting optical power by bringing the passive waveguide region into close proximity to the PLC waveguide; A heater electrode formed on the top of the WBG to control the temperature of the WBG; And PLC-based wavelength tunable WDM-PON system, characterized in that it comprises an optical fiber formed on the silicon substrate at the other end of the PLC waveguide. The method of claim 19, PLC-based wavelength tunable WDM-PON system, characterized in that the fixed substrate is a silicon substrate. The method of claim 19, The semiconductor chip is a wavelength variable WDM-PON system, characterized in that formed on the InP substrate. The method of claim 19, The material of the passive waveguide region is a PLC-based WV-PON system, characterized in that made of at least one of InP-based semiconductor, polymer, nitride and silica. 20. The waveguide structure of claim 19, wherein the waveguide structure of the semiconductor chip is A PLC-based wavelength tunable WDM-PON system comprising at least one of a channel waveguide, a ridge-loaded waveguide, and a rib waveguide. The method of claim 19, The directional coupler employs a leak-mode grating-assisted directional coupler (LM-GADC) method that satisfies a phase-matching condition between two waveguides by counting a lattice at a junction between the semiconductor chip waveguide and the PLC waveguide. PLC-based wavelength tunable WDM-PON system, characterized in that using. The method of claim 19, The directional coupler uses an etched surface-mount coupler (ESMC) to etch a portion of the semiconductor chip and to form the waveguide using a dielectric medium having a refractive index similar to that of the PLC waveguide. Wavelength variable WDM-PON system. The method of claim 19, The passive waveguide region is a PLC-based wavelength tunable WDM-, characterized in that the size is reduced from the active waveguide region to the passive waveguide region in order to optically couple the light generated in the active waveguide region with the PLC waveguide. PON system. The method of claim 26, The passive waveguide region is a PLC-based wavelength tunable WDM-PON system, characterized in that the light generated from the active waveguide region is transmitted to the PLC waveguide before reaching the end of the passive waveguide region. The method of claim 19, The PLC waveguide is formed in a structure that is reduced in size toward the one end of the PLC waveguide in a portion in contact with the passive waveguide region to increase the size of the propagated light, PLC-based wavelength tunable WDM-PON system, characterized in that the light reflected from the WBG is not reflected at one end of the PLC waveguide. The method of claim 19, PLC-based wavelength tunable WDM-PON system, characterized in that the monitoring photodetector (mPD) for monitoring the size of the light generated in the semiconductor chip is mounted on the side of the semiconductor chip. The method of claim 19, The PLC waveguide is a PLC-based WV-PON system, characterized in that formed in the spot-size converter structure in which the beam in the PLC waveguide is enlarged to increase the optical coupling efficiency with the optical fiber. The method of claim 19, The PLC waveguide WWW-PON system of the PLC-based wavelength tunable, characterized in that the optical fiber is manually aligned on the fixed substrate using V-groove. The method of claim 19, Wherein the WBG is a PLC-based wavelength tunable WDM-PON system, characterized in that made of silica (silica) WBG when the wavelength tunable range is small. The method of claim 19, The WBG is a PLC-based WV-PON system, characterized in that made of a polymer-based WBG when the wavelength variable range is large. The method of claim 19, The semiconductor chip further comprises a phase adjusting unit for fine-tuning the wavelength, the fine-tuning of the wavelength is PLC-based wavelength variable WDM-PON system, characterized in that performed by controlling the amount of current injected into the phase adjusting unit. The method of claim 19, The PLC waveguide further includes a phase adjusting unit for fine tuning the wavelength, wherein the fine tuning of the wavelength is PLC-based wavelength tunable WDM-PON system, characterized in that made by the electro-optic effect or thermo-optic effect of the PLC waveguide. The method of claim 19, The semiconductor chip is composed of a Fabry-Perot laser diode (FP-LD) array, The Fabry-Perot laser diode array corresponds to the WBG array in a one-to-one manner to form an external resonant laser (ECL) array, PLC-based WV-PON system. The method of claim 36, The WBG array is a PLC-based WV-PON system, characterized in that the wavelength of each of the WBG is independently changed by the thermo-optic effect. The method of claim 36, PLC-based WDM-PON system, characterized in that the monitoring photodetector (mPD) for monitoring the light output from the Fabry-Perot laser diode array is configured in an array form. The method of claim 36, Multi-wavelength optical signals at the output stage of the external resonance laser (ECL) array are wavelength-multiplexed by a wavelength multiplexer monolithicly integrated in the PLC waveguide so that a single optical fiber pigtail is provided. -PON system.

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