KR100743172B1 - Photoelectric converter in e-pon system and method for transmitting optical signal - Google Patents

Abstract

A photoelectric transformer in an E-PON(Ethernet Passive Optical Network) system and an optical signal transmission or receipt method using the same are provided to eliminate a spurious phenomenon occurring in a broadcast signal outputting apparatus by an interference phenomenon in accordance with a non linear property of an optical cable and thereby to maintain signal quality of broadcasting channels in a cable TV or an MA TV when an E-PON optical signal is coupled with a broadcasting optical signal and the coupled signal is transmitted in an FTTH(Fiber To The Home) network. A photoelectric transformer in an E-PON(Ethernet Passive Optical Network) system comprises the first duplex filter(411), an RF mixer(413), the second duplex filter(412), and a laser diode(414). The first duplex filter(411) receives an electric signal with two kinds of frequencies, namely f1 and f2, and separates the f1 from the f2. The RF mixer(413) converts an electric signal having the f1, separated by the first duplex filter(411), into an electric signal having a frequency of f3. The second duplex filter(412) couples the electric signal having the f3, transformed by the RF mixer(413), with the electric signal having the f2. The laser diode(414) transforms the electric signal, coupled by the second duplex filter(412), into an optical signal.

Description

Photoelectric Converter and E-PON System and Method for Transmitting Optical Signal in E-PON System

1 is a block diagram showing the configuration of an E-PON system using a general overlay technique.

Figure 2 is a block diagram showing the internal configuration of a typical E-PON system opto-electric converter.

Figure 3 is a block diagram showing the internal configuration of another general E-PON system opto-electric converter.

Figure 4 is a block diagram showing the internal configuration of an optical signal transmission and reception apparatus using an overlay scheme according to an embodiment of the present invention.

5 is a block diagram showing the internal configuration of an optical signal transmission and reception apparatus using an overlay scheme according to another embodiment of the present invention.

6 is a flowchart illustrating a method of transmitting and receiving an optical signal using an overlay scheme according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

410: transmitting side optical / electric converter 440: receiving side optical / electric converter

411: first duplexer filter 412: second duplex filter

413: RF mixer 414: optical / electric laser diode

430: splitter 441: photodiode

442: third duplexer 443: fourth duplexer

The present invention relates to an overlay video signal transmission / reception apparatus and method of FTTH E-PON.

The recent Internet craze is fundamentally changing the paradigm of the communication environment. As the demand for high speed / high quality data of users increases, the market size is rapidly increasing. This is due to the spread of ADSL, a technology that realizes high speed internet while utilizing existing copper wire. However, users' demands are beyond the speed limits of ADSL, and one of the technologies that replace ADSL is PON.

PON is an optical subscriber network technology that provides fiber-based, high-speed data services to businesses, SOHO, and homes. The typical structure of a PON is a structure in which an optical line termination (OLT) is installed in a central office (CO) and a plurality of optical network units (ONUs) are connected to one OLT through a 1: n optical star coupler. to be. Here, the ONU converts an optical signal into a signal of an RF frequency, or conversely, converts a signal of an RF frequency into an optical signal.

1 is a block diagram illustrating an E-PON network employing a general overlay signal transmission method.

As shown in FIG. 1, the E-PON system may include an OLT 10, a splitter 20, an ONU 30, and the like. Of course, the E-PON system includes more components, but only those components that can exhibit the characteristics of the present invention are shown in FIG.

The OLT 10 may include an OLT CATV module 11 for providing a broadcast service and an OLT PON module 15 for providing a data service. The OLT CATV module 11 receives data from a service provider, and the OLT PON module 15 is connected to the Internet.

The broadcast signal is transmitted from the program provider or service provider and received by the opto-electric converter 12 in the OLT CATV module 11. The received broadcast signal is amplified by the optical amplifier 13 and then output through the wavelength division multiplexing module 14 which multiplexes the PON data signal with the broadcast signal.

The splitter 20 branches the optical signal transmitted from the OLT 10 at various ratios and delivers the splitted signal to each ONU 30 located at the subscriber end. In this case, the ONU 30 may be composed of an ONU CATV module 31 and an ONU PON module 34 like the OLT 10. The wavelength division multiplexing module 32 in the ONU CATV module 31 extracts only a signal of a broadcast wavelength among two wavelengths transmitted and received in the PON network. The optical / electric converter 33 converts the extracted broadcast wavelength optical signal into an RF signal and transmits it to a subscriber set-top box or a TV through a coaxial cable. On the other hand, the signal of the phase and downlink data wavelength extracted by the wavelength division multiplexing module 32 is transmitted to the ONU PON module 34, thereby providing the Internet service to the subscriber.

As described above, data transmission and reception by inserting two signals having different wavelengths into one optical cable is called an overlay technique. When data is transmitted and received through the overlay technique, a spurious phenomenon occurs.

The spurious phenomenon refers to a phenomenon in which interference between the E-PON optical signal and the broadcasting optical signal occurs due to the nonlinear characteristic of the optical cable when the optical signal is transmitted by the overlay technique. This spurious phenomenon is also referred to as unnecessary radiation (不 要 輻射), which is a signal generated outside the band, including the unwanted harmonics, harmonics other than the frequency desired by the radio transmitter. Such a spurious phenomenon interferes with other communication, so it is strictly limited to a certain limit by a radio wave method. In particular, the concept includes a case where local oscillation frequency or its harmonics are leaked to the outside in a super receiver of a radio or television.

Accordingly, the present invention is to solve the problems according to the prior art, by converting and transmitting the electrical signal of the frequency affected by the spurious phenomenon of the electrical signal having two kinds of frequencies to another frequency, due to harmonics An object of the present invention is to provide an apparatus and method for transmitting and receiving an optical signal of an overlay technique in an E-PON system that prevents a spurious phenomenon.

The transmitting-side photoelectric converter according to an aspect of the present invention receives an electrical signal having a frequency of f1 and f2, and separates the electrical signal of f1 separated by the first duplex filter and the first duplex filter, respectively. An RF mixer for converting an electric signal having a frequency of?, A second duplex filter for coupling an electric signal of f3 converted by the RF mixer and an electric signal of f2 separated by the first duplex filter, and the second duplex filter It may include a laser diode to convert the combined electrical signal into an optical signal.

In addition, the receiving-side photoelectric converter according to another aspect of the present invention receives an optical signal overlaid with an electrical signal having a frequency of f2, f3, the photodiode converting into an electrical signal, the electrical conversion of the photodiode A first duplex filter for separating a signal into an electrical signal having a frequency of f2 and f3, an RF mixer for frequency converting an electrical signal of f3 separated by the first duplex filter into an electrical signal having a frequency of f1, and the RF The mixer may include a second duplex filter that combines and outputs an electrical signal of f1 frequency-converted and an electrical signal of f2 separated by the first duplex filter.

In addition, the receiving-side photoelectric converter according to another aspect of the present invention receives an optical signal overlaid with an electrical signal having a frequency of f1, f2, and converts the photodiode and the photodiode converted into an electrical signal The electronic device may include a band reject filter for removing a bandwidth in which spurious phenomenon occurs in the electrical signal. In this case, the receiving side opto-electric converter may further include an RF amplifier for amplifying the electrical signal output from the band reject filter.

According to another aspect of the present invention, an optical signal transmission and reception method includes an optical signal transmission apparatus receiving a frequency of f1 and f2, and converting an electrical signal of frequency f1 into an electrical signal having a frequency of f3, the optical signal The transmitting device combines the electrical signals of the f2, f3 and converts them into an optical signal and outputs the optical signal, the optical signal receiving device receives the optical signal, converts it into an electrical signal, separated into an electrical signal having a frequency of f2 and f3 And the optical signal receiving apparatus converts an electrical signal of f3 into an electrical signal having a frequency of f1 among the separated signals, and the optical signal receiving apparatus combines electrical signals of f1 and f2 frequencies. It may include.

In this case, the step of converting the electrical signal of the frequency f1 into the electrical signal of the frequency f3 by the optical signal transmitting apparatus is characterized in that using an RF mixer, the optical signal transmitting apparatus combining the electrical signals of the frequency f1, f3 Alternatively, the optical signal receiving unit may combine an electrical signal of f1 and f2 frequencies using a duplex filter.

Hereinafter, an optical signal transceiving apparatus and method thereof of an overlay technique in an E-PON system according to the present invention will be described in detail with reference to the accompanying drawings.

2 is a block diagram showing an internal configuration of a general E-PON optoelectric converter.

As shown in FIG. 2, the general optical / electric converter 100 includes an RF coupling unit 110 and an optical / electric laser diode 120. In addition, there is a coupler 130 for coupling the optical signal output from the photoelectric converter 100 with the E-PON optical signal.

First, the RF combiner 110 of the optical / electric converter 100 according to the configuration of FIG. 2 combines a cable TV and a satellite broadcast signal. The photo / electric laser diode 120 of the photo / electric converter 100 then converts the combined RF signal into an optical signal having a wavelength of λ1.

An optical signal now having a wavelength of λ 1 is transmitted to the coupler 130. Meanwhile, the coupler 130 receives an E-PON optical signal having a wavelength of λ 3, and couples and outputs the optical signals of λ 1 and λ 3. As such, FIG. 2 illustrates an optical / electric converter for implementing an overlay technique by converting a broadcast signal and an E-PON signal into optical signals having different wavelengths.

3 is a block diagram illustrating an internal configuration of another general E-PON optoelectric converter.

The optical / electric converter 200 of FIG. 3 uses two optical / electric laser diodes 220 and 230 to convert a satellite signal having a wavelength of λ1 and a broadcast signal combining a MATV signal and a cable TV signal having a wavelength of λ2. Will be sent. This corresponds to the application of the photoelectric converter of FIG. Let's take a closer look at this.

The RF combiner 210 combines the satellite signal and the MA TV signal, and the first photoelectric laser diode 220 converts the combined RF signal into an optical signal having a wavelength of λ1. Meanwhile, the cable broadcast signal is immediately transmitted to the second optical / electric laser diode 230 and converted into an optical signal having a wavelength of λ2.

The coupler 240 in the opto-electric converter 200 now combines the optical signals of [lambda] 1 and [lambda] 2 and outputs them to another coupler 250. The other coupler 250 receives not only the optical signals of λ1 and λ2, but also the E-PON optical signal λ3, and couples and outputs them.

However, when transmitting optical signals in a single cable at the same time, interference between the optical signals occurs due to the nonlinear characteristics of the cable. Crosstalk between optical signals generated by the nonlinear nature of the cable increases in proportion to the cable length. That is, when the broadcast signal is transmitted in the E-PON signal path, the electrical signal of the short-wavelength E-PON optical signal is induced into the long-wavelength broadcast optical signal. The signal thus induced appears in the broadcast frequency band at the output terminal of the broadcast receiver, which appears in some channel bands of the broadcast and degrades the quality of some broadcast channels. Hereinafter, an E-PON system for solving the problem will be described.

4 is a block diagram showing an internal configuration of an overlay optical signal transmitting and receiving device according to an embodiment of the present invention.

As shown in FIG. 4, the apparatus for transmitting and receiving an optical signal may include an optical / electric converter 310 of a transmitter, a coupler 320, a splitter 330 of a receiver, and an optical / electric converter 340. have. The structure of the transmission-side photoelectric converter 310 according to the present embodiment is almost similar to that of the photoelectric converter 200 described with reference to FIG. 2. Therefore, detailed operation description of the transmission-side optoelectric converter will be omitted.

The opto-electric converter 310 of the transmitting end outputs an optical signal having frequencies of λ 1 and λ 3. The splitter 330 combines the received optical signals into optical signals of λ 1 and optical signals of λ 3, respectively. Of these, the optical signal of λ3 is used for E-PON data communication, and only the optical signal of λ1 is input to the optical / electric converter 340.

The photoelectric converter 340 of the receiver receives an optical signal of λ1. A photo diode 341 of the photoelectric converter 340 converts an optical signal of λ 1 into an electrical signal of f 1. The signal output from the photodiode 341 is input to the band reject filter 342, and the band reject filter 342 removes only a 62.5 MHz band signal from the electrical signal and outputs the signal to the RF amplifier 343. Now, the RF amplifier 343 amplifies the strength of the electrical signal from which the signal of the 62.5MHz band is removed and outputs it to the cable TV.

FIG. 4 is characterized in that a spurious phenomenon is removed by adding a band rejection filter that removes only a frequency of a specific band and passes a signal of a remaining band to a receiver configured in a conventional FTTH network. The spurious phenomenon affecting the overlay broadcast signal is induced by the E-PON optical signal, which appears in the form of multiplication frequency of 62.5Mhz in the broadcasting device. The opto-electric converter 340 of the receiver removes the harmonics of 62.5 MHz by using a band rejection filter 342 of 62.5 MHz. Of course, due to the nature of the band-stop filter, other frequency bands are passed, so that only the spurious induced by the E-PON optical signal is removed at the output of the broadcast signal.

Of course, the band reject filter 342 in this embodiment is described as a filter for removing the band of 62.5MHz, the band to be removed by the band reject filter 342 can be changed as much.

5 is a block diagram showing an internal configuration of an overlay optical signal transmitting and receiving device according to another embodiment of the present invention.

As shown in FIG. 5, the opto-electric converter 410 includes two duplex filters 411 and 412 and an RF mixer 413.

The opto-electric converter 410 of the transmitting end receives a broadcast signal having a frequency of (f1, f2). The broadcast signal thus received is separated using the first duplex filter 411. In detail, the first duplex filter 411 separates the broadcast signal of the frequency f1 affected by the spurious phenomenon. Thereafter, the separated f1 broadcast signal is transferred to the RF mixer 413, and the RF mixer 413 performs a frequency conversion operation of f3 on the frequency signal of f1.

The second duplex filter 412 recombines the broadcast signal of f2 and the broadcast signal of f3, and the photo / electric laser diode 414 converts the combined RF signal into an optical signal having a wavelength of λ1 to couple the coupler 420. To send. The coupler 420 combines the broadcast signal having the wavelength of λ 1 and the E-PON optical signal λ 3 and transmits the combined signal to the receiving end.

The splitter 430 of the receiving end transmits only the optical signal of λ1 among the optical signals having frequencies of λ1 and λ3 to the photodiode 441. The photodiode 441 of the receiver optoelectric converter 440 converts the optical signal of λ1 into an electrical signal having a frequency of f2 and f3. The third duplex filter 442 separates the broadcast signals having frequencies of f3 and f2 from the electrical signals extracted by the photodiode 441. The broadcast signal having a frequency of f3 is delivered to the RF mixer 444, and the RF mixer 444 converts the broadcast signal of f3 into a broadcast signal having a frequency of f1. A broadcast signal having frequencies f1 and f2 is transmitted to the fourth duplex filter 443, and the fourth duplex filter 443 combines the two signals and outputs the combined signals.

After all, the signal of the broadcasting frequency band affected by the E-PON data optical signal is separated and frequency converted, and then converted into an optical signal and transmitted. The receiving E / O converter converts the received optical signal into an electrical signal having a frequency of the original band by using a duplexer filter and an RF mixer to output a broadcast signal.

6 is a flowchart illustrating a method of transmitting and receiving an optical signal of an overlay method according to another embodiment of the present invention.

The optical signal transmitting apparatus receives a broadcast electric signal in which frequencies of f1 and f2 are mixed, respectively (S601). The optical signal transmission apparatus performs the operation of separating the electrical signal for each frequency (S602). This signal separation process may be performed by a duplex filter. If it is assumed that the frequency affected by the spurious phenomenon is f1, the optical signal transmission apparatus frequency-converts the broadcast signal of f1 to the broadcast signal of f3 (S603).

Now, the optical signal transmission apparatus combines the broadcast signals of f2 and f3 (S604), and converts them into optical signals again (S605). The optical signal generated in this way is transmitted to the optical signal receiving device via the optical fiber cable and other optical network equipment (S606).

The optical signal receiving apparatus receives an optical signal output in step S206 and converts the optical signal into an electrical signal having a frequency of f2 and f3 (S607). The optical signal receiving apparatus separates the electric signals of f2 and f3 which are mixed by using the duplex filter (S608).

Of these, the frequency electrical signal at f3 is a signal originally at the frequency of f1. The optical signal receiving apparatus converts a broadcast signal of f3 into a broadcast signal having a frequency of f1 by using an RF mixer or the like (S609). In this manner, the optical signal receiving apparatus can obtain the frequency broadcast signals f1 and f2, and provide the broadcast service to the user by combining and outputting the signals (S610).

Although the present invention has been described in detail through the representative embodiments, those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention. I will understand. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the claims below but also by the equivalents of the claims.

As described above, the present invention provides an overlay video signal transmission / reception device including a BRF (Band Rejection Filter) or an overlay video signal transmission / reception device including a duplex filter and an RF mixer, thereby providing an E-PON in an FTTH network. When combining and transmitting an optical signal and a broadcast optical signal, spurious phenomena appearing in the broadcast signal output device can be eliminated due to interference due to the nonlinear characteristics of the optical cable, and thus the signal of the cable TV or MA TV broadcast channel The effect is that quality can be maintained.

Claims (7)

a first duplex filter which receives an electrical signal having a frequency of f1 and f2 and separates them respectively; An RF mixer for converting an electrical signal of f1 separated by the first duplex filter into an electrical signal having a frequency of f3; A second duplex filter coupling an electrical signal of f3 converted by the RF mixer and an electrical signal of f2 separated by the first duplex filter; And And a laser diode to convert an electrical signal coupled by the second duplex filter into an optical signal. an optical diode that receives an optical signal overlaid with an electrical signal having a frequency of f2 and f3, and converts the optical signal into an electrical signal; A first duplex filter separating the electrical signal converted by the photodiode into an electrical signal having a frequency of f2 and f3, respectively; An RF mixer for frequency converting an electrical signal of f3 separated by the first duplex filter into an electrical signal having a frequency of f1; And a second duplex filter for combining and outputting an electrical signal of f1 frequency-converted by the RF mixer and an electrical signal of f2 separated by the first duplex filter. an optical diode that receives an optical signal overlaid with an electrical signal having a frequency of f1 and f2 and converts the optical signal into an electrical signal; And a band stop filter for removing a bandwidth in which a spurious phenomenon occurs in the electrical signal converted by the photodiode. The method of claim 3, And an RF amplifier configured to amplify the electrical signal output from the band reject filter. The optical signal transmitting apparatus receives a frequency of f1 and f2, respectively, and converts an electrical signal of frequency f1 into an electrical signal having a frequency of f3; The optical signal transmitting apparatus comprises the steps of: combining the electrical signals of the f2, f3, and converts them into optical signals; The optical signal receiving apparatus includes: receiving an optical signal, converting the optical signal into an electrical signal, and separating the optical signal into an electrical signal having frequencies of f2 and f3; The optical signal receiving apparatus converting an electric signal of f3 into an electric signal having a frequency of f1 among the separated signals; And Optical signal receiving apparatus comprising the step of combining the electrical signal of the frequency f1, f2. The method of claim 5, And converting, by the optical signal transmission device, an electrical signal of frequency f1 into an electrical signal of frequency f3 using an RF mixer. The method of claim 5, And combining the electrical signals of the f1 and f3 frequencies by the optical signal transmitting apparatus or combining the electrical signals of the f1 and f2 frequencies by the optical signal receiving apparatus comprises using a duplex filter.

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