JP2014068092A - Optical communication system - Google Patents

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JP2014068092A
JP2014068092A JP2012210356A JP2012210356A JP2014068092A JP 2014068092 A JP2014068092 A JP 2014068092A JP 2012210356 A JP2012210356 A JP 2012210356A JP 2012210356 A JP2012210356 A JP 2012210356A JP 2014068092 A JP2014068092 A JP 2014068092A
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communication system
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JP6026832B2 (en
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Sang-Yuep Kim
サンヨプ キム
Jun Terada
純 寺田
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Nippon Telegraph and Telephone Corp
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Abstract

PROBLEM TO BE SOLVED: To provide an economical optical communication system that can secure optical power budget in a high multi-value signal.SOLUTION: An optical communication system 301 is an optical communication system in which an ONU 100 and an OLT 200 are connected by an optical fiber 150. The OLT 200 makes light of an optical source 21 for downlink transmission to the ONU 100 into pump light generating Stimulated Brillouin Scattering (SBS) light in the optical fiber 150. The ONU 100 transmits an uplink optical signal with an optical frequency included in the frequency band of the SBS light generated from the pump light to the OLT 200.

Description

本発明は誘導ブリルアン散乱（ＳＢＳ：Ｓｔｉｍｕｌａｔｅｄ Ｂｒｉｌｌｏｕｉｎ Ｓｃａｔｔｅｒｉｎｇ）を利用した光増幅を行う光通信システムに関する。   The present invention relates to an optical communication system that performs optical amplification using Stimulated Brillouin Scattering (SBS).

高多値信号を使用したシステムは、制限されたアナログ帯域幅にもＳｈａｎｎｏｎ ｃａｐａｃｉｔｙ理論に近接するシステムスループットを実現できる。このシステムは、信号対雑音比を犠牲にしているため、ＰＯＮ構成で光パワーバジェットを確保する必要がある。光パワーバジェットを確保する第１の手法としては、局側光端末回線装置（ＯＬＴ：Ｏｐｔｉｃａｌ Ｌｉｎｅ Ｔｅｒｍｉｎａｌ）や加入者側光端末回線装置（ＯＮＵ：Ｏｐｔｉｃａｌ Ｎｅｔｗｏｒｋ Ｕｎｉｔ）に高出力パワー光源を使用する手法がある。   Systems using high multilevel signals can achieve system throughput close to Shannon capacity theory, even in limited analog bandwidth. Since this system sacrifices the signal-to-noise ratio, it is necessary to ensure an optical power budget with a PON configuration. As a first method for securing an optical power budget, a method using a high output power light source for a station side optical terminal line device (OLT) or a subscriber side optical terminal line device (ONU: Optical Network Unit). There is.

また、光パワーバジェットを確保する第２の手法としては、局側光端末回線装置（ＯＬＴ：Ｏｐｔｉｃａｌ Ｌｉｎｅ Ｔｅｒｍｉｎａｌ）及び加入者側光端末回線装置（ＯＮＵ：Ｏｐｔｉｃａｌ Ｎｅｔｗｏｒｋ Ｕｎｉｔ）にコヒーレント受信器を置いて光局部発振器からの光を用いて光受信信号を増幅する手法も提案されている。   Further, as a second method for securing the optical power budget, a coherent receiver is placed in the station side optical terminal line device (OLT) and the subscriber side optical terminal line device (ONU: Optical Network Unit). A method of amplifying an optical reception signal using light from an optical local oscillator has also been proposed.

しかし、第１及び第２の手法は、対応を各ＯＮＵに施すことになりシステムコストを増大させるという課題があった。そこで、光パワーバジェットを確保するため、ＯＤＮ（Ｏｐｔｉｃａｌ Ｄｉｓｔｒｉｂｕｔｉｏｎ Ｎｅｔｗｏｒｋ）区間で信号光を増幅させる手法も知られている。   However, the first and second methods have a problem of increasing the system cost because the correspondence is applied to each ONU. Therefore, a method for amplifying signal light in an ODN (Optical Distribution Network) section is also known in order to secure an optical power budget.

その手法としては、ＯＤＮ区間に個別光増幅器を使用する手法（第３の手法）がある。ＯＤＮ区間で光増幅をするには個別デバイスであるＤＦＡ（ｒａｒｅ ｅａｒｔｈ ｄｏｐｅｄ ｆｉｂｅｒ ａｍｐｌｉｆｉｅｒ）あるいはＳＯＡ（ｓｅｍｉｃｏｎｄｕｃｔｏｒ ｏｐｔｉｃａｌ ａｍｐｌｉｆｉｅｒ）を使う。   As the technique, there is a technique (third technique) using an individual optical amplifier in the ODN section. In order to perform optical amplification in the ODN section, DFA (rare earth doped fiber amplifier) or SOA (semiconductor optical amplifier) which is an individual device is used.

また、ＯＤＮ区間で光増幅をする手法としては、ＳＢＳ光増幅現象をＰＯＮ（Ｐａｓｓｉｖｅ Ｏｐｔｉｃａｌ Ｎｅｔｗｏｒｋ）システムの物理層に適用する手法（第４の手法）がある。ＳＢＳ光増幅の原理を以下に説明する（非特許文献１を参照。）。ポンプ光源から所定の光強度より大きい光（ポンプ光）を光ファイバに入力すると、ポンプ光の周波数よりおおよそ１１ＧＨｚ下にストークスシフトされたストークス光が発生する。ストークス光は、ポンプ光と逆方向に伝搬しながら増幅される。ストークス光は同一の周波数の信号光を増幅することができる。そのとき、利得帯域幅は数十ＭＨｚのブリルアン線幅になる。ポンプ光を一定の帯域幅で変調することで、ブリルアン線幅を増加させて利得帯域幅を拡張することができる。   In addition, as a technique for performing optical amplification in the ODN section, there is a technique (fourth technique) in which the SBS optical amplification phenomenon is applied to the physical layer of a PON (Passive Optical Network) system. The principle of SBS optical amplification will be described below (see Non-Patent Document 1). When light (pump light) greater than a predetermined light intensity is input from the pump light source to the optical fiber, Stokes light that is Stokes shifted approximately 11 GHz below the frequency of the pump light is generated. Stokes light is amplified while propagating in the opposite direction to the pump light. Stokes light can amplify signal light of the same frequency. At that time, the gain bandwidth is a Brillouin line width of several tens of MHz. By modulating the pump light with a constant bandwidth, the Brillouin line width can be increased and the gain bandwidth can be expanded.

Ｎ．Ａ．Ｏｌｓｓｏｎ ａｎｄ Ｊ．Ｐ．ＶＡＮ ＤＥＲ ＺＩＥＬ，“Ｃｈａｒａｃｔｅｒｉｓｔｉｃｓ ｏｆ ａ Ｓｅｍｉｃｏｎｄｕｃｔｏｒ Ｌａｓｅｒ Ｐｕｍｐｅｄ Ｂｒｉｌｌｏｕｉｎ Ａｍｐｌｉｆｉｅｒ ｗｉｔｈ Ｅｌｅｃｔｒｏｎｉｃａｌｌｙ Ｃｏｎｔｒｏｌｌｅｄ Ｂａｎｄｗｉｄｔｈ”， Ｊ．Ｌｉｇｈｔｗａｖｅ Ｔｅｃｈｎｏｌ．， ｖｏｌ． ＬＴ−５， ｎｏ．１， １４７−１５３，１９８７．N. A. Olsson and J.M. P. VAN DER ZIEL, “Characteristics of a Semiconductor Laser Pumped Brillouin Amplifier with Electrically Controlled Bandwidth”, J. VAN DER ZIEL, “Characteristics of a Semiconductor Laser Pumped Brillouin Amplifier with Electrically Controlled Bandwidth”. Lightwave Technol. , Vol. LT-5, no. 1, 147-153, 1987.

しかし、第３の手法は光増幅用のデバイスが必要であり、第４の手法もポンプ光源やポンプ光を伝送路に注入するための光部品が必要になるなど、システムが複雑で高価になるという課題があった。そこで、上記課題を解決すべく、本発明は、高多値信号における光パワーバジェットを確保できる経済的な光通信システムを提供することを目的とする。   However, the third method requires a device for optical amplification, and the fourth method also requires a pump light source and an optical component for injecting pump light into the transmission path, and the system becomes complicated and expensive. There was a problem. Therefore, in order to solve the above-described problems, an object of the present invention is to provide an economical optical communication system that can secure an optical power budget in a high multilevel signal.

上記目的を達成するために、本発明は、ＯＬＴ側に高出力ＬＤを搭載し、各ＯＮＵからの上り通信をＯＤＮ上でＳＢＳ光増幅可能とすることで、ＯＮＵに搭載するＬＤ出力の要求条件を下げることで光通信システムの経済化を実現する。   In order to achieve the above object, the present invention is equipped with a high-power LD on the OLT side, and enables upstream communication from each ONU to be SBS optically amplified on the ODN. The economics of the optical communication system is realized by lowering.

具体的には、本発明に係る光通信システムは、加入者側光端末回線装置（ＯＮＵ：Ｏｐｔｉｃａｌ Ｎｅｔｗｏｒｋ Ｕｎｉｔ）と局側光端末回線装置（ＯＬＴ：Ｏｐｔｉｃａｌ Ｌｉｎｅ Ｔｅｒｍｉｎａｌ）とを光ファイバで接続した光通信システムであって、
前記ＯＬＴは、前記ＯＮＵへの下り送信用光源の光を、前記光ファイバで誘導ブリルアン散乱（ＳＢＳ：Ｓｔｉｍｕｌａｔｅｄ Ｂｒｉｌｌｏｕｉｎ Ｓｃａｔｔｅｒｉｎｇ）光を発生させるポンプ光としており、
前記ＯＮＵは、前記ポンプ光で発生する前記ＳＢＳ光の周波数帯域に含まれる光周波数の上り光信号を前記ＯＬＴへ送信することを特徴とする。 Specifically, the optical communication system according to the present invention includes an optical fiber in which a subscriber-side optical terminal line device (ONU) and a station-side optical terminal line device (OLT) are connected by an optical fiber. A communication system,
The OLT uses light from a light source for downstream transmission to the ONU as pump light that generates stimulated Brillouin scattering (SBS) light in the optical fiber,
The ONU transmits an upstream optical signal having an optical frequency included in a frequency band of the SBS light generated by the pump light to the OLT.

本光通信システムは、ＳＢＳ光増幅のためのポンプ光源をＯＬＴの下り光信号の送信用光源に兼用させている。このため、上記第４の手法で課題となっていたポンプ光源やポンプ光を伝送路に注入するための光部品が不必要になり、システムがシンプルで経済的になる。従って、本発明は、高多値信号における光パワーバジェットを確保できる経済的な光通信システムを提供することができる。   In this optical communication system, a pump light source for SBS optical amplification is also used as a light source for transmitting an OLT downstream optical signal. For this reason, the pump light source and the optical component for injecting the pump light into the transmission path, which are problems in the fourth method, are not necessary, and the system becomes simple and economical. Therefore, the present invention can provide an economical optical communication system that can secure an optical power budget in a high-value signal.

本発明に係る光通信システムの前記ＯＬＴは、前記ＯＮＵへの下り送信用光源の光を、直交周波数分割多重（ＯＦＤＭ：Ｏｒｔｈｏｇｏｎａｌ Ｆｒｅｑｕｅｎｃｙ Ｄｉｖｉｓｉｏｎ Ｍｕｌｔｉｐｌｅｘｉｎｇ）変調を行うＯＦＤＭ光変調部を有することを特徴とする。ＯＦＤＭ信号のフラットなスペクトラム特性により、別途の利得平坦光デバイスを使わずにＳＢＳ利得帯域の拡張ができる。   The OLT of the optical communication system according to the present invention includes an OFDM optical modulation unit that performs orthogonal frequency division multiplexing (OFDM) modulation on light of a light source for downlink transmission to the ONU. . Due to the flat spectrum characteristics of the OFDM signal, the SBS gain band can be expanded without using a separate gain flat optical device.

本発明に係る光通信システムは、ＰＯＮ構成としてＯＮＵを複数とすることができる。そして、各ＯＮＵは上り信号について同一光周波数としてもよいし、前記ＯＮＵは複数であり、前記ＯＮＵ毎に上り光信号のサブキャリアが異なるとしてもよい。   The optical communication system according to the present invention can have a plurality of ONUs as the PON configuration. Each ONU may have the same optical frequency for the upstream signal, and there may be a plurality of ONUs, and the subcarrier of the upstream optical signal may be different for each ONU.

本発明に係る光通信システムの前記ＯＬＴは、複数の波長の下り光信号を合波して前記光ファイバに結合することができる。本光通信システムを波長分割多重方式（ＷＤＭ：Ｗａｖｅｌｅｎｇｔｈ Ｄｉｖｉｓｉｏｎ Ｍｕｌｔｉｐｌｅｘｉｎｇ）とし、伝送量を増大させることができる。   The OLT of the optical communication system according to the present invention can combine downstream optical signals having a plurality of wavelengths and couple them to the optical fiber. The optical communication system can be a wavelength division multiplexing (WDM) system to increase the transmission amount.

本発明は、高多値信号における光パワーバジェットを確保できる経済的な光通信システムを提供することができる。   The present invention can provide an economical optical communication system that can secure an optical power budget in a high-level multilevel signal.

本発明に係る光通信システムの構成を説明する図である。It is a figure explaining the structure of the optical communication system which concerns on this invention. 本発明に係る光通信システムのＯＬＴとＯＮＵの光送信周波数の配置を説明する図である。It is a figure explaining arrangement | positioning of the optical transmission frequency of OLT and ONU of the optical communication system which concerns on this invention. 本発明に係る光通信システムの構成を説明する図である。It is a figure explaining the structure of the optical communication system which concerns on this invention. 本発明に係る光通信システムのＯＬＴとＯＮＵの光送信周波数の配置を説明する図である。It is a figure explaining arrangement | positioning of the optical transmission frequency of OLT and ONU of the optical communication system which concerns on this invention. 本発明に係る光通信システムの構成を説明する図である。It is a figure explaining the structure of the optical communication system which concerns on this invention. 本発明に係る光通信システムのＯＬＴとＯＮＵの光送信周波数の配置を説明する図である。It is a figure explaining arrangement | positioning of the optical transmission frequency of OLT and ONU of the optical communication system which concerns on this invention.

添付の図面を参照して本発明の実施形態を説明する。以下に説明する実施形態は本発明の実施例であり、本発明は、以下の実施形態に制限されるものではない。なお、本明細書及び図面において符号が同じ構成要素は、相互に同一のものを示すものとする。また、枝番号を付さずに説明している場合は、当該符号の全ての枝番号に共通する説明である。   Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components. Moreover, when it demonstrates without attaching a branch number, it is description common to all the branch numbers of the said code | symbol.

（実施形態１）
図１は、本実施形態の光通信システム３０１を説明する図である。光通信システム３０１は、ＯＮＵ１００とＯＬＴ２００とを光ファイバ１５０で接続した光通信システムである。ＯＬＴ２００は、ＯＮＵ１００への下り送信用光源２１の光を、光ファイバ１５０でＳＢＳ光を発生させるポンプ光としている。ＯＮＵ１００は、ポンプ光で発生するＳＢＳ光の周波数帯域に含まれる光周波数の上り光信号をＯＬＴ２００へ送信する。 (Embodiment 1)
FIG. 1 is a diagram for explaining an optical communication system 301 of the present embodiment. The optical communication system 301 is an optical communication system in which the ONU 100 and the OLT 200 are connected by an optical fiber 150. The OLT 200 uses the light of the downstream transmission light source 21 to the ONU 100 as pump light that generates SBS light by the optical fiber 150. The ONU 100 transmits an upstream optical signal having an optical frequency included in the frequency band of the SBS light generated by the pump light to the OLT 200.

ＯＬＴ２００は、光トランシーバの光送信部に増幅臨界値を超える高出力光源２１を有する。さらに、ＯＬＴ２００は、波長ロッカ２２を有し、高出力光源２１をストークスシフトを考慮した所望の光周波数に合わせる。さらに、ＯＬＴ２００は、ＯＮＵ１００への下りデータで高出力光源２１からの光を変調する光変調部２３を有する。なお、ＯＦＤＭ変調を行う場合、光変調部２３はＯＦＤＭ光変調部となる。ＯＬＴ２００は、高出力光源２１からの光（供給光）を光変調部２３を介して光ファイバ１５０に結合する。   The OLT 200 includes a high-power light source 21 that exceeds the amplification critical value in the optical transmission unit of the optical transceiver. Further, the OLT 200 includes a wavelength locker 22 and adjusts the high-power light source 21 to a desired optical frequency considering the Stokes shift. Further, the OLT 200 includes a light modulation unit 23 that modulates light from the high-power light source 21 with downstream data to the ONU 100. In addition, when performing OFDM modulation, the optical modulation unit 23 becomes an OFDM optical modulation unit. The OLT 200 couples light (supply light) from the high-power light source 21 to the optical fiber 150 via the light modulation unit 23.

ＯＮＵ１００は、光トランシーバの光送信部に光源１１、波長ロッカ１２、及び光変調部１３を有する。波長ロッカ１２は、ＯＬＴ２００からの光で光ファイバ１５０に生じるストークス光の光周波数に含まれる光を光源１１に出力させる。光変調部１３は、ＯＬＴ２００への上りデータで光源１１からの光を変調する。なお、ＯＦＤＭ変調を行う場合、変調部１３はＯＦＤＭ光変調部となる。また、ｎはＯＮＵ１００の数を示している。本実施形態はｎが１であるＳＳ（Ｓｉｎｇｌｅ Ｓｔａｒ）方式にも同等な効果がある。   The ONU 100 includes a light source 11, a wavelength locker 12, and an optical modulation unit 13 in the optical transmission unit of the optical transceiver. The wavelength locker 12 causes the light source 11 to output light included in the optical frequency of the Stokes light generated in the optical fiber 150 by the light from the OLT 200. The light modulator 13 modulates the light from the light source 11 with the upstream data to the OLT 200. When performing OFDM modulation, the modulation unit 13 is an OFDM optical modulation unit. N indicates the number of ONUs 100. The present embodiment has an equivalent effect even in an SS (Single Star) system in which n is 1.

図２は、光通信システム３０１のＯＬＴ２００とＯＮＵ１００の光送信周波数の配置を説明する図である。ＯＬＴ２００は、供給光を光ファイバ１５０に出力する。供給光は、ＳＢＳ光増幅用のポンプ光としてストークスシフト分低い光周波数の位置にストークス光を発生させる。このストークス光の帯域がＳＢＳ利得帯域となり、光ファイバ１５０がＳＢＳ利得媒質として作用する。ＯＮＵ１００は、供給光の周波数からストークスシフト分低い光周波数の上り光信号を出力する。ＯＮＵ１００からの上り光信号はＯＬＴ２００へ伝搬されながら増幅される。なお、図２では、上り光信号をストークスシフト分低い光周波数としているが、ストークスシフト分高い光周波数としてもよい。   FIG. 2 is a diagram for explaining the arrangement of optical transmission frequencies of the OLT 200 and the ONU 100 of the optical communication system 301. The OLT 200 outputs supply light to the optical fiber 150. The supplied light generates Stokes light as a pump light for amplifying SBS light at a position having an optical frequency lower by the Stokes shift. The Stokes light band becomes the SBS gain band, and the optical fiber 150 acts as an SBS gain medium. The ONU 100 outputs an upstream optical signal having an optical frequency that is lower than the frequency of the supplied light by a Stokes shift. The upstream optical signal from the ONU 100 is amplified while being propagated to the OLT 200. In FIG. 2, the upstream optical signal has an optical frequency lower by the Stokes shift, but may have an optical frequency higher by the Stokes shift.

ＯＬＴ２００は、供給光を光ファイバ１５０に常時出力する。ＯＮＵ１００の上り光信号の送信タイミングにかかわらず光ファイバ１５１を常に励起し、上り光信号を常に増幅可能状態としておく。具体的には、光変調部２３は、ＯＬＴ２００からＯＮＵ１００への下りデータが無い場合、ダミーデータを用いて高出力光源２１からの供給光を変調して光ファイバ１５０へ出力する。このようにダミーデータを用いることでＳＢＳ利得帯域を広げることができる。また、光変調部２３は、ＯＬＴ２００からＯＮＵ１００への下りデータがある場合、下りデータを用いて高出力光源２１からの供給光を変調して光ファイバ１５０へ出力する。これによりＯＬＴ２００は光ファイバ１５０を励起するとともに、下り光信号をＯＮＵ１００へ到達させることができる。   The OLT 200 always outputs supply light to the optical fiber 150. The optical fiber 151 is always excited regardless of the transmission timing of the upstream optical signal of the ONU 100, and the upstream optical signal is always in an amplifiable state. Specifically, when there is no downlink data from the OLT 200 to the ONU 100, the light modulation unit 23 modulates the supply light from the high output light source 21 using the dummy data and outputs the modulated light to the optical fiber 150. In this way, the SBS gain band can be expanded by using dummy data. Further, when there is downlink data from the OLT 200 to the ONU 100, the light modulation unit 23 modulates the supply light from the high output light source 21 using the downlink data and outputs the modulated light to the optical fiber 150. As a result, the OLT 200 can excite the optical fiber 150 and allow the downstream optical signal to reach the ONU 100.

光変調器２３がＯＦＤＭ変調を行う場合（ＯＦＤＭ光変調器の場合）、供給光は図２のように所定の帯域幅を持つことになる。下りのデータがない場合は、任意のダミーデータでＯＦＤＭ変調を行う。これに伴い、ストークス光も同等の帯域幅に広がり、フラットな利得スペクトラムとなりＳＢＳ利得帯域を広げることができる。ＯＮＵ１００の波長ロッカ１２は、上りＯＦＤＭ光信号の光周波数がＳＢＳ利得帯域に収まるように光源１１の光周波数を合わせる。   When the optical modulator 23 performs OFDM modulation (in the case of the OFDM optical modulator), the supplied light has a predetermined bandwidth as shown in FIG. When there is no downstream data, OFDM modulation is performed with arbitrary dummy data. Along with this, Stokes light also spreads to the same bandwidth, resulting in a flat gain spectrum and the SBS gain bandwidth can be expanded. The wavelength locker 12 of the ONU 100 matches the optical frequency of the light source 11 so that the optical frequency of the uplink OFDM optical signal is within the SBS gain band.

（実施形態２）
図３は、本実施形態の光通信システム３０２を説明する図である。光通信システム３０２と図１の光通信システム３０１との違いは、光通信システム３０２がＯＮＵ１００毎に上り光信号のサブキャリアが異なる点である。なお、光通信システム３０２は、ＯＬＴ２００もＯＮＵ１００もＯＦＤＭ変調を行う。図４は、光通信システム３０２のＯＬＴ２００とＯＮＵ１００の光送信周波数の配置を説明する図である。各ＯＮＵ１００が出力する全ての上り光信号の光周波数は、ＯＬＴ２００からの供給光によるＳＢＳ利得帯域内に収まっている。 (Embodiment 2)
FIG. 3 is a diagram illustrating the optical communication system 302 of the present embodiment. A difference between the optical communication system 302 and the optical communication system 301 of FIG. 1 is that the optical communication system 302 has different subcarriers of the upstream optical signal for each ONU 100. In the optical communication system 302, both the OLT 200 and the ONU 100 perform OFDM modulation. FIG. 4 is a diagram for explaining the arrangement of optical transmission frequencies of the OLT 200 and the ONU 100 of the optical communication system 302. The optical frequencies of all upstream optical signals output from each ONU 100 are within the SBS gain band of the light supplied from the OLT 200.

より具体的に説明する。ＯＮＵ１００の光変調器１３は光キャリア抑圧ＯＦＤＭ光変調器である。光キャリア抑圧ＯＦＤＭ光変調器は、光キャリアを抑圧し、ＯＦＤＭ光信号のうち、所望のサブキャリアのみを残して他のサブキャリアを消去して出力することができる。例えば、ＯＮＵ１００−１は、ＳＢＳ利得帯域に含まれる光周波数ｆ１のサブキャリアのみの光信号を出力する。同様に、ＯＮＵ１００−ｎは、ＳＢＳ利得帯域に含まれる光周波数ｆｎのサブキャリアのみの光信号を出力する。なお、「光キャリア抑圧」とは、各ＯＮＵがｆ１〜ｆｎでサブキャリアを違えていても、光キャリア成分による干渉を抑圧するという意味である。   This will be described more specifically. The optical modulator 13 of the ONU 100 is an optical carrier suppression OFDM optical modulator. The optical carrier suppressing OFDM optical modulator can suppress the optical carrier and erase and output other subcarriers in the OFDM optical signal while leaving only the desired subcarrier. For example, the ONU 100-1 outputs an optical signal of only the subcarrier having the optical frequency f1 included in the SBS gain band. Similarly, the ONU 100-n outputs an optical signal of only a subcarrier having an optical frequency fn included in the SBS gain band. “Optical carrier suppression” means that even if each ONU has different subcarriers in f1 to fn, interference due to the optical carrier component is suppressed.

ＯＬＴ２００の波長ロッカ２２及びＯＮＵ１００の波長ロッカ１２の動作は実施形態１の説明と同じである。すなわち、波長ロッカ１２は、各ＯＮＵ１００の光源１１からの光の光周波数を同一とし、ＯＦＤＭ変調した上り光信号がＳＢＳ利得帯域に収まるような光周波数の光を光源１１に出力させる。したがって、ＯＮＵ１００ごとに光周波数が異なる上り光信号はすべて光ファイバ１５０でＳＢＳ増幅される。   The operations of the wavelength locker 22 of the OLT 200 and the wavelength locker 12 of the ONU 100 are the same as those described in the first embodiment. That is, the wavelength locker 12 makes the light frequency of the light from the light source 11 of each ONU 100 the same, and causes the light source 11 to output light having an optical frequency such that the upstream optical signal modulated by OFDM falls within the SBS gain band. Therefore, all upstream optical signals having different optical frequencies for each ONU 100 are SBS amplified by the optical fiber 150.

（実施形態３）
図５は、本実施形態の光通信システム３０３を説明する図である。光通信システム３０３と図１の光通信システム３０１との違いは、光通信システム３０３がＷＤＭ方式を採用している点にある。ＯＬＴ２００’は、複数の波長の下り光信号をアレイ導波路回折格子（ＡＷＧ：Ａｒｒａｙｅｄ Ｗａｖｅｇｕｉｄｅ Ｇｒａｔｉｎｇ）２４で合波して光ファイバ１５０に結合する。ＯＮＵ１００はＡＷＧ１５２を介して光ファイバ１５０に接続する。 (Embodiment 3)
FIG. 5 is a diagram illustrating the optical communication system 303 of the present embodiment. The difference between the optical communication system 303 and the optical communication system 301 in FIG. 1 is that the optical communication system 303 adopts the WDM system. The OLT 200 ′ combines downstream optical signals having a plurality of wavelengths with an arrayed waveguide grating (AWG) 24 and couples the optical signals to the optical fiber 150. The ONU 100 is connected to the optical fiber 150 via the AWG 152.

図６は、光通信システム３０３のＯＬＴ２００’とＯＮＵ１００の光送信周波数の配置を説明する図である。ＯＬＴ２００’は各ＯＮＵ１００に対応する光トランシーバの送信部を有する。ＯＬＴ２００’のそれぞれの波長ロッカ２２はそれぞれの高出力光源２１に図６の下り光信号の光周波数で発振させる。ＯＮＵ１００のそれぞれの波長ロッカ１２は、光源１１に図６の上り光信号の光周波数で発振させる。上りの光信号はそれぞれの供給光によるＳＢＳ利得帯域に含まれるため、ＷＤＭ上り信号はすべて光ファイバでＳＢＳ増幅される。   FIG. 6 is a diagram illustrating the arrangement of optical transmission frequencies of the OLT 200 ′ and the ONU 100 of the optical communication system 303. The OLT 200 ′ has an optical transceiver transmission unit corresponding to each ONU 100. Each wavelength locker 22 of the OLT 200 'causes each high-power light source 21 to oscillate at the optical frequency of the downstream optical signal in FIG. Each wavelength locker 12 of the ONU 100 causes the light source 11 to oscillate at the optical frequency of the upstream optical signal in FIG. Since the upstream optical signal is included in the SBS gain band of each supplied light, all the WDM upstream signals are SBS amplified by the optical fiber.

以下は、本実施形態の光通信システムを説明したものである。
（概要）
本光通信システムは、ＳＢＳから増幅機能を持つＯＦＤＭ−ＰＯＮシステムの構成技術である。本光通信システムは、ＯＬＴに存在する下り送信用光源をＳＢＳポンプ光源に兼用することで、ＯＤＮの光ファイバでＳＢＳ光増幅を発生させ上り信号を光増幅する。
（効果）
（１）高多値信号を伝送フォーマットとするＯＦＤＭ−ＰＯＮシステムにおいて、ＯＤＮで別途のアクティブ光デバイスを使わずにＯＮＵの送信光パワーの要求条件を低めることができ、ＰＯＮシステムの経済性確保ができる。
（２）ＯＦＤＭ信号のフラットなスペクトラム特性により、別途の利得平坦光デバイスを使わずに利得帯域幅の拡張ができる。 The following describes the optical communication system of the present embodiment.
(Overview)
This optical communication system is a configuration technology of an OFDM-PON system having an amplification function from SBS. In this optical communication system, the downlink transmission light source existing in the OLT is also used as the SBS pump light source, thereby generating SBS optical amplification in the ODN optical fiber and optically amplifying the upstream signal.
(effect)
(1) In an OFDM-PON system using a high multilevel signal as a transmission format, the ODN transmission optical power requirements can be reduced without using a separate active optical device in the ODN, thereby ensuring economic efficiency of the PON system. it can.
(2) Due to the flat spectrum characteristic of the OFDM signal, the gain bandwidth can be expanded without using a separate gain flat optical device.

１１：光源
１２：波長ロッカ
１３：光変調部
２１：高出力光源
２２：波長ロッカ
２３：光変調部
２４：ＡＷＧ
１００、１００’：ＯＮＵ
１５０：光ファイバ
１５１：スプリッタ
１５２：ＡＷＧ
２００、２００’：ＯＬＴ 11: Light source 12: Wavelength locker 13: Light modulator 21: High power light source 22: Wavelength locker 23: Light modulator 24: AWG
100, 100 ': ONU
150: Optical fiber 151: Splitter 152: AWG
200, 200 ': OLT

Claims (4)

加入者側光端末回線装置（ＯＮＵ：Ｏｐｔｉｃａｌ Ｎｅｔｗｏｒｋ Ｕｎｉｔ）と局側光端末回線装置（ＯＬＴ：Ｏｐｔｉｃａｌ Ｌｉｎｅ Ｔｅｒｍｉｎａｌ）とを光ファイバで接続した光通信システムであって、
前記ＯＬＴは、前記ＯＮＵへの下り送信用光源の光を、前記光ファイバで誘導ブリルアン散乱（ＳＢＳ：Ｓｔｉｍｕｌａｔｅｄ Ｂｒｉｌｌｏｕｉｎ Ｓｃａｔｔｅｒｉｎｇ）光を発生させるポンプ光としており、
前記ＯＮＵは、前記ポンプ光で発生する前記ＳＢＳ光の周波数帯域に含まれる光周波数の上り光信号を前記ＯＬＴへ送信することを特徴とする光通信システム。 An optical communication system in which a subscriber side optical terminal line device (ONU: Optical Network Unit) and a station side optical terminal line device (OLT: Optical Line Terminal) are connected by an optical fiber,
The OLT uses light from a light source for downstream transmission to the ONU as pump light that generates stimulated Brillouin scattering (SBS) light in the optical fiber,
The optical communication system, wherein the ONU transmits an upstream optical signal having an optical frequency included in a frequency band of the SBS light generated by the pump light to the OLT. 前記ＯＬＴは、前記ＯＮＵへの下り送信用光源の光を、直交周波数分割多重（ＯＦＤＭ：Ｏｒｔｈｏｇｏｎａｌ Ｆｒｅｑｕｅｎｃｙ Ｄｉｖｉｓｉｏｎ Ｍｕｌｔｉｐｌｅｘｉｎｇ）変調を行うＯＦＤＭ光変調部を有することを特徴とする請求項１に記載の光通信システム。   2. The optical communication according to claim 1, wherein the OLT includes an OFDM optical modulation unit that performs orthogonal frequency division multiplexing (OFDM) modulation on light of a downstream transmission light source to the ONU. system. 前記ＯＮＵは複数であり、前記ＯＮＵ毎に上り光信号のサブキャリアが異なることを特徴とする請求項２に記載の光通信システム。   The optical communication system according to claim 2, wherein there are a plurality of ONUs, and a subcarrier of an upstream optical signal is different for each ONU. 前記ＯＬＴは、複数の波長の下り光信号を合波して前記光ファイバに結合することを特徴とする請求項１から３のいずれかに記載の光通信システム。   4. The optical communication system according to claim 1, wherein the OLT combines downstream optical signals having a plurality of wavelengths and couples the optical signals to the optical fiber. 5.
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