KR20070069799A - Optical module of wavelength division multiplexing passive optical network for monitoring output of light source - Google Patents

Abstract

An optical module of a WDM(Wavelength Division Multiplexing) PON(Passive Optical Network) for monitoring output of a light source is provided to quickly sense whether an optical transmitter malfunctions by monitoring output of the light source, thereby improving reliability of the WDM PON. A light source(110) is equipped. A beam splitter(120) splits a beam emitted from the light source(110) into an output beam(S1) which becomes an uplink signal or a downlink signal for bidirectional communication and a sensing beam(S2) for monitoring strength of the output beam(S1). An optical receiver(130) senses strength of the sensing beam(S2).

Description

Optical module of wavelength division multiplexing passive optical network for monitoring output of light source

1 is a block diagram showing a wavelength division multiplex passive optical subscriber network.

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

3 is a block diagram showing an optical module of the WDM-PON according to another embodiment of the present invention.

4 is a block diagram showing an optical module of the WDM-PON according to another embodiment of the present invention.

5 is a block diagram showing an optical module of the WDM-PON according to another embodiment of the present invention.

** Explanation of symbols in main part of drawing **

110: light source

120: optical separator

130: optical receiver

The present invention relates to an optical module of a wavelength division multiplex passive optical subscriber network, and more particularly, to an optical module of a wavelength division multiple passive passive optical subscriber network for monitoring the output of a light source.

Recently, the telecommunications industry sees FTTH (fiber to the home) as the ultimate solution for the rapidly growing broadcast, Internet and multimedia services. Among them, a passive optical network (PON), which is particularly easy to maintain and maintain, is adopted.

PON refers to a structure in which a single fiber is connected to a central office and a remote node, and then a separate fiber is connected from a local base station to each optical network unit. PON has the advantage of significantly reducing the cost of laying fiber cables than one-to-one connections from central base stations to subscribers.

PON can be divided into time division multiplexing (TDM) and wavelength division multiplexing (WDM). TDM-PON is economical because it provides communication service to all subscribers using one optical transceiver. In contrast, WDM-PON assigns unique wavelengths to subscribers, enabling high-speed, high-capacity data transmission, and excellent security. In addition, there is an advantage of easy performance improvement, such as narrowing the channel interval or increasing the transmission rate for each channel in accordance with the increase in subscriber and service demand.

Despite the above advantages, WDM-PON is not yet economical because it requires a light source having each specific oscillation wavelength and an additional wavelength stabilization circuit for stabilizing the wavelength of the light source. Recently, wideband light source with easy wavelength management, Fabry-Perot laser, or reflective semiconductor optical waveguide, which is immersed in incoherent light, to realize economical WDM-PON Research into using an optical amplifier as a light source for WDM has been conducted.

In general, WDM-PON uses a double-molded structure to minimize the length of the light path. That is, the central base station is connected to the local base station installed in the neighboring area of the subscribers by one main optical fiber, and the local base station is connected to each subscriber by an independent distribution optical fiber. The multiplexed downlink signals are transmitted to the local base station through the trunk fiber. The downlink signal is again demultiplexed at the local base station and transmitted to each subscriber via a distributed fiber. The uplink signal output from the subscribers is transmitted to the local base station, and the local base station multiplexes the uplink signal and transmits it to the central base station.

In WDM-PON, a large amount of data is transmitted at high speed using a unique wavelength assigned to each subscriber. Thus, if an unexpected uplink or downlink transmitter fails, or a trunk or split fiber failure occurs, the link may be broken and large amounts of data transmitted may be lost, even in a short time. Therefore, in order to increase the reliability of the WDM-PON, there is a need for a method capable of quickly detecting a failure of an uplink transmitter or a downlink transmitter or a failure of a trunk fiber or a distribution fiber.

Korean Patent Laid-Open Publication No. 2005-0092680 discloses an apparatus for remotely monitoring an optical path under the heading "Optical path monitoring device in a bidirectional wavelength division multiplexing passive optical subscriber network using a laser immersed in an incoherent light source". . The optical path is monitored through the reflector reflecting only the monitoring signal band among the downlink signal and the monitoring signal output from the optical splitter. However, the document does not disclose monitoring the output of an optical transmitter.

One of the reasons that the link is broken in the WDM-PON is that the optical transmitter of either up or down signal is not working or the output is weak. Therefore, it is necessary to continuously monitor the output of the light source used as the optical transmitter to check whether the light source is operating normally.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide an optical module of a wavelength division multiplex type passive optical subscriber network for monitoring the output of a light source in order to solve the above problems.

The present invention for solving the above technical problem provides an optical module of the wavelength division multiplex passive optical subscriber network for performing bidirectional communication between the central base station and a plurality of optical subscriber. The optical module detects the light source, an optical splitter for splitting the light emitted from the light source into an output light that is an uplink signal or a downlink signal for bidirectional communication and a detection light for monitoring the intensity of the output light, and the intensity of the detection light. It includes a photoreceiver.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present embodiment is not limited to the embodiment disclosed below and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the invention to those skilled in the art. Like numbers refer to like elements throughout.

1 is a block diagram showing a wavelength division multiplex passive optical subscriber network.

Referring to FIG. 1, a wavelength division multiplexing passive optical network (WDM-PON) may include a central office (CO), a local base station (RN), and a subscriber network (ONU). an optical network unit). The main optical fiber (MF) connects the central base station (CO) and the local base station (RN), and the distribution optical fiber (DF) connects the local base station (RN) and the subscriber network (ONU).

WDM-PON performs two-way communication using two wavelength bands. The central base station CO receives upstream signals from the local base station RN or transmits downlink signals through the trunk fiber MF. Here, the downlink signal refers to a signal transmitted from the central base station (CO) to the subscriber network (ONU), and the uplink signal refers to a signal transmitted from the subscriber network (ONU) to the central base station (CO). For convenience of description, hereinafter, the downlink signal is transmitted through the A band wavelength, and the uplink signal is referred to as the B band wavelength.

The central base station CO includes a plurality of optical receivers RX1, ..., RXn, optical transmitters TX1, ..., TXn, band separation filters FT1, ..., FTn, and a first wavelength division. And a wavelength division multiplexer (WDM1).

The optical receivers RX1, ..., RXn receive the upstream signals and detect them as electrical signals. The optical transmitters TX1, ..., TXn transmit downlink signals. In this case, the optical transmitters TX1 to TXn have an A band wavelength. The band separation filters FT1, ..., FTn separate / combine the light of the A band wavelength and the light of the B band wavelength.

The first wavelength division multiplexer WDM1 simultaneously transmits the light of the A band wavelength and the light of the B band wavelength to perform multiplexing / demultiplexing. In detail, the first wavelength division multiplexer WDM1 multiplexes the input downlink signal and outputs the downlink signal to the trunk fiber MF. In addition, the first wavelength division multiplexer WDM1 demultiplexes the input upstream signal and outputs the demultiplexed signal to the band separation filters FT1 to FTn. The first wavelength division multiplexer WDM1 may be an arrayed waveguide grating (AWG).

The local base station RN is connected to the central base station CO through the trunk fiber MF and to the subscriber network ONU through the distribution fiber DF1,..., DFn. The local base station RN includes a second wavelength division multiplexer WDM2. The second wavelength division multiplexer WDM2 demultiplexes the input downlink signal and outputs the downlinked signal to the distribution optical fibers DF1,..., DFn. In addition, the second wavelength division multiplexer WDM2 multiplexes the input upstream signal and outputs the same to the trunk fiber MF. The second wavelength division multiplexer WDM2 may be a waveguide thermal grating.

The subscriber network ONU includes a plurality of subscribers ONU1, ..., ONUn. Each subscriber (ONU1, ..., ONUn) is connected one-to-one with distributed optical fibers (DF1, ..., DFn). The subscribers (ONU1, ..., ONUn) have separate band separation filters (FT'1, ..., FT'n), optical receivers (RX'1, ..., RX'n) and optical transmitters, respectively. (TX'1, ..., TX'n). The optical receivers RX'1, ..., RX'n receive downlink signals and detect them as electrical signals. The optical transmitters TX'1, ..., TX'n transmit uplink signals. At this time, the optical transmitters TX'1, ..., TX'n have a B band wavelength. The band separation filters FT'1, ..., FT'n separate / combine the light of the A band wavelength and the light of the B band wavelength.

In the WDM-PON configured as described above, the optical transmitters TX1, ..., TXn of the central base station CO and the optical transmitters TX'1, ... of the respective subscribers ONU1, ..., ONUn. , TX'n) shall each be able to emit a separate band of light. Monitoring the intensity of the emitted light is an optical module according to an embodiment of the present invention.

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

Referring to FIG. 2, the optical module 100 includes a light source 110, a beam splitter 120, and an optical receiver 130.

The light source 110 emits light of a predetermined wavelength. Preferably, the light source 110 may be a Fabry-Perot laser diode and may be a reflective semiconductor optical amplifier. However, the light source 110 may be any other type of laser diode that emits light, without being limited to the types listed above.

The optical separator 120 splits the input light into two lights. That is, the light emitted from the light source 110 is separated into the output light S1 and the detection light S2 while passing through the optical separator 120. The output light S1 is vertically reflected by the optical separator 120 and output, and the detection light S2 proceeds through the optical separator 120. The intensity of the output light S1 and the detection light S2 depends on the split ratio of the optical separator 120.

The output light S1 branched to the optical separator 120 becomes an output for generating an uplink signal or a downlink signal for bidirectional communication in the WDM-PON.

The detection light S2 is incident on the light receiver 130. The photoreceiver 130 senses the intensity of incident light, and a photodiode may be used. That is, in order to monitor the intensity of the output light S1, the intensity of the detection light S2 branched to the light source 110 is sensed. This is because the detection light and 2) the output light S1 are branched from the same light source 110. If the detection light S2 has an intensity less than or equal to the set value, the intensity of the output light S1 also becomes a predetermined level or less.

In the present invention, by placing the optical receiver 130 in front of the light source 110, it is possible to accurately monitor the intensity of the light output from the light source (110). Therefore, it is possible to check whether light having a normal output is emitted from the light source 110, so it is easy to know whether an uplink signal or a downlink signal is disturbed in the WDM-PON. In addition, the optical module according to the present invention can be made compact and inexpensive since its structure is simple.

The light source 110, the optical separator 120, and the optical receiver 130 may be provided in a thio-can (TO-CAN) structure to package one. The thio-can structure includes a stem 180 and a number of leads 190. The light source 110 is disposed on the stem 180 via the first sub-mount 115. The optical receiver 130 is disposed on the stem 180 via the second sub-mount 135. Optical splitter 120 may also be disposed on stem 180 via a separate sub-mount (not shown). The sub-mounts 115 and 135 are made of a ceramic material and electrically insulate the conductor stem 180. The lead 190 penetrates the stem 180 and is electrically connected to the light source 110 or the light receiver 130.

3 is a block diagram showing an optical module of the WDM-PON according to another embodiment of the present invention.

Referring to FIG. 3, the optical module 200 includes a light source 210, an optical separator 220, and an optical receiver 230. Unlike the embodiment of FIG. 2, the light source 210 emits light in the vertical axis instead of the horizontal axis.

The optical separator 220 splits the input light into two lights. That is, the light emitted from the light source 210 is separated into the output light S1 and the detection light S2 while passing through the optical separator 220. The output light S1 proceeds through the optical separator 220, and the detection light S2 is vertically reflected by the optical splitter 220. The light receiver 230 detects the intensity of the incident detection light S2. The rest is the same as the embodiment of Figure 2, so the description thereof will be omitted.

4 is a block diagram showing an optical module of the WDM-PON according to another embodiment of the present invention.

Referring to FIG. 4, the optical module 300 includes a light source 310, an optical separator 320, and an optical receiver 330. The light source 310 emits light in the horizontal axis. The light emitted from the light source 310 passes through the optical separator 320 and is separated into an output light S1 and a detection light S2. The output light S1 is vertically reflected by the optical separator 320 and output, and the detection light S2 passes through the optical separator 320.

The detection light S2 is incident on the light receiver 330. The optical receiver 330 detects the intensity of incident light. Unlike the embodiment of FIG. 2, the light receiver 330 is a photodiode having a reflective mirror facet 332. An example of a photodiode having a reflective mirror may refer to Korean Patent Publication No. 2005-0046893 by the present applicant. The path of the sensing light S2 may be changed through the reflecting mirror 332 to facilitate the installation and alignment of the light receiver 330. The rest is the same as the embodiment of Figure 2, so the description thereof will be omitted.

5 is a block diagram showing an optical module of the WDM-PON according to another embodiment of the present invention.

Referring to FIG. 5, the optical module 400 includes a light source 410, an optical separator 420, and an optical receiver 430. The light source 410 emits light in the longitudinal axis. The light emitted from the light source 410 is separated into the output light S1 and the detection light S2 while passing through the light separator 420. The output light S1 proceeds through the optical separator 420, and the detection light S2 is vertically reflected by the optical separator 420. The light receiver 230 detects the intensity of the incident detection light S2.

The detection light S2 is incident on the light receiver 430. The optical receiver 430 senses the intensity of the incident light. Unlike the embodiment of FIG. 2, the optical receiver 430 is a photodiode having a reflective mirror 432. The rest is the same as the embodiment of Figure 2, so the description thereof will be omitted.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, the terms and expressions used in the present specification are used for the purpose of description and do not have any limitation, and the use of such terms and expressions is illustrated. It is not intended to exclude equivalents of the described components or portions thereof, and various modifications are of course possible within the scope of the claimed invention. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

As described above, according to the present invention, it is possible to accurately monitor the intensity of light output from the light source. It is simple in structure and can be miniaturized and inexpensive.

In addition, by monitoring the output of the light source it is possible to quickly detect whether or not the optical transmitter. Therefore, the reliability of the WDM-PON is improved.

Claims (4)

In the optical module of the wavelength division multiplex passive optical subscriber network for performing bidirectional communication between the central base station and a plurality of optical subscribers, Light source; A beam splitter for splitting the light emitted from the light source into an output light that is an uplink signal or a downlink signal for bidirectional communication and a detection light for monitoring the intensity of the output light; And An optical module of a wavelength division multiplex passive optical subscriber network comprising an optical receiver for sensing the intensity of the detection light. The method of claim 1, And the optical receiver is a photodiode having a reflective mirror facet. The method of claim 1, And the light source is a Fabry-Perot laser diode. The method of claim 1, The light source is an optical module of a wavelength division multiplex passive optical subscriber network, characterized in that the reflective semiconductor optical amplifier.

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