JP3701556B2 - Multi-wavelength light source - Google Patents

Multi-wavelength light source Download PDF

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Publication number
JP3701556B2
JP3701556B2 JP2000266125A JP2000266125A JP3701556B2 JP 3701556 B2 JP3701556 B2 JP 3701556B2 JP 2000266125 A JP2000266125 A JP 2000266125A JP 2000266125 A JP2000266125 A JP 2000266125A JP 3701556 B2 JP3701556 B2 JP 3701556B2
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Japan
Prior art keywords
wavelength
light source
output
wavelengths
multiplexing
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JP2000266125A
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JP2002076503A (en
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淳一 可児
正満 藤原
光啓 手島
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Nippon Telegraph and Telephone Corp
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Nippon Telegraph and Telephone Corp
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Priority to JP2000266125A priority Critical patent/JP3701556B2/en
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Priority to CA002487187A priority patent/CA2487187C/en
Priority to CA2487177A priority patent/CA2487177C/en
Priority to CA002487181A priority patent/CA2487181C/en
Priority to CA002352680A priority patent/CA2352680C/en
Priority to US09/900,613 priority patent/US6831774B2/en
Publication of JP2002076503A publication Critical patent/JP2002076503A/en
Priority to US10/655,675 priority patent/US6924924B2/en
Priority to US10/826,571 priority patent/US7068412B2/en
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  • Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
  • Lasers (AREA)
  • Semiconductor Lasers (AREA)
  • Optical Communication System (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は多波長光源に関し、特に、波長多重通信システムで用いられ、それぞれ異なる中心波長を有する複数の入力光から波長の異なる複数の光キャリアを一括発生する多波長光源に関する。
【０００２】
【従来の技術】
従来、光通信において、波長多重信号（ＷＤＭ：Ｗａｖｅｌｅｎｇｔｈ Ｄｉｖｉｓｉｏｎ Ｍｕｌｔｉｐｌｅｘｉｎｇ）に使用する平坦な光スペクトルを有する多波長一括発生法として、非線形光ファイバ透過によるＳｕｐｅｒｃｏｎｔｉｎｕｕｍ発生により得られた平坦化連続光スペクトルを光フィルタで切り出す手法や、光短パルス発生により得られた光パルスの繰り返し周波数間隔で周波数軸上に並んだ光スペクトルを、逆の周波数特性を有する光フィルタに透過させる手法がある。
【０００３】
【発明が解決しようとする課題】
しかし、Ｓｕｐｅｒｃｏｎｔｉｎｕｕｍ発生における平坦化多波長発生法においては、非線形光ファイバの製作は容易ではなく、時間とコストがかかるという課題があった。また、光短パルス発生により得られた光スペクトルを逆特性光フィルタに透過させる平坦化多波長発生法においては、平坦な光スペクトルを実現するために、光短パルスのデューティと、それに応じた光フィルタの透過特性の設計が困難であるという課題があった。
【０００４】
本発明は上記の課題を解決するためになされたもので、複雑な光回路の設計を行うこと無く、簡易かつ低コストな構成で、光スペクトルの平坦化されたＷＤＭ信号を干渉雑音を伴うことなく一括して発生することができる多波長光源を提供することを目的とする。
【０００５】
【課題を解決するための手段】
上記の目的を達成するために請求項１の発明は、それぞれ異なる中心波長を有する複数の入力光から波長の異なる複数の光キャリアを一括発生する多波長光源において、前記複数の入力光のうち、その波長が奇数番目の入力光を合波する第１合波手段と、前記複数の入力光のうち、その波長が偶数番目の入力光を合波する第２合波手段と、前記第１合波手段の出力光に対して所定のサイドモードを発生するように変調を行なう第１変調手段と、前記第２合波手段の出力光に対して所定のサイドモードを発生するように変調を行なう第２変調手段と、前記第１および第２の変調手段の変調出力を偏波合成する合成手段と、前記合成手段からの多波長化されて合成された出力から前記波長の異なる複数の光キャリアを分離する分離手段とを備えた形態の多波長光源を実施した。
【０００６】
請求項２の発明は、請求項１に記載の多波長光源において、前記第１変調手段は、その出力において（２Ｎ＋ｍ）個の波長（Ｎは自然数，ｍは整数）の光パワーが所定範囲にあるようにサイドモードを発生し、前記第２変調手段は、その出力において（２Ｎ−ｍ）個の波長（Ｎは自然数，ｍは整数）の光パワーが所定範囲にあるようにサイドモードを発生する形態の多波長光源を実施した。
【０００７】
請求項３の発明は、それぞれ異なる中心波長を有する複数の入力光から波長の異なる複数の光キャリアを一括発生する多波長光源において、前記複数の入力光のうち、その波長が奇数番目の入力光を合波する第１合波手段と、前記複数の入力光のうち、その波長が偶数番目の入力光を合波する第２合波手段と、前記第１の合波手段の合波出力と第２の合波手段の合波出力の偏波が直交するように偏波合成する合成手段と、前記合成手段の出力光を所定のスペクトル形状で変調出力する変調手段と、前記変調手段からの多波長化されて変調された出力から前記波長の異なる複数の光キャリアを分離する分離手段とを備えた形態の多波長光源を実施した。
【０００８】
請求項４の発明は、請求項１または３に記載の多波長光源において、前記第１および第２の変調手段／前記変調手段は、前記合成手段／前記変調手段の出力においてそれぞれの出力波長の光パワーがほぼ一定となるように調整してサイドモードを出力するように変調を行なう形態の多波長光源を実施した。
【０００９】
請求項５の発明は、請求項４に記載の多波長光源において、前記変調手段は、隣り合う前記複数の入力光に応じた出力光のサイドモードのうち、当該隣り合う入力光波長のほぼ中間の波長と前記入力光波長の間のサイドモードがほぼ一定の光パワーとなり、互いに同一波長で、前記ほぼ中間の波長のサイドモードが前記一定の光パワーのほぼ半分となるようにサイドモードを出力する形態の多波長光源を実施した。
【００１０】
【作用】
上記のように構成された本発明に係る多波長光源においては、波長が隣り合う光から発生した同一波長の２つのサイドモード光は、その偏波が互いに直交するために干渉雑音を引き起こすことがない。このため、すべての波長で劣化がなく、等間隔の波長グリッドに隙間が生じない。
【００１１】
【発明の実施の形態】
［第１実施形態］
図１は本発明に係る多波長光源の第１実施形態を示す構成図である。
本実施形態に係る多波長光源では、それぞれ異なる単一の中心波長の光を発生する２ｎ（ｎは１以上の自然数）個の光源１０1〜１０2nからの入力光を２分割して２系統の合波、変調処理を行ない、各変調結果を偏波合成し、これを波長の異なる複数のキャリアに分離して最終的な出力を得る構成とされている。以下、この構成および動作について詳細に説明する。
【００１２】
図１において、光源１０1，１０2，１０3，１０4，…１０2n-1，１０2nには例えば、分布帰還型（ＤＦＢ）半導体レーザや、外部共振器型半導体レーザを使用する。各光源はそれぞれ単一の中心波長で発光し、それぞれの中心波長は異なっており、周波数軸上で添え字の番号順に等間隔で並んでいる。
【００１３】
２１および２２は、例えばアレー型導波路回折格子や光カプラを使用した光合波器であり、光合波器２１は奇数番目の各光源による光を合波する。光合波器２２は、光合波器２１とは独立に偶数番目の各光源による光を合波する。光合波器２１による合波出力は変調器２７により変調され、光合波器２２による合波出力は変調器２８により変調され、変調器２７と２８は例えば、入力された合波光に強度変調および位相変調を施すものであり、具体的には、リチウムナイオベートを媒質とした１つのマッハツェンダ型強度変調器と、リチウムナイオベートを媒質とした１つの位相変調器を直列に接続したものを用いることができる。
【００１４】
両変調器２７と２８の出力光は偏波合成器３０によって合成された後、分離フィルタで構成した分波器４０において波長毎に分波され、波長の異なる複数の光キャリアが一括的に発生される。
【００１５】
ここで図２（ａ）は、変調器２７により生成された、偏波合成前のＡ点における、奇数番目の多波長化された光スペクトルの一部を拡大して示し、図２（ｂ）は、偏波合成前のＢ点における、偶数番目の多波長化された光スペクトルの一部を拡大して示している。
【００１６】
両図に示したように、変調器２７によるサイドモード光のスペクトル形状（図２（ａ））と変調器２８によるサイドモード光のスペクトル形状（図２（ｂ））は必ずしも同一でなくともよい。偏波合成器３０によって偏波合成した後に、図３に示すようにすべての波長の光パワーがほぼ均一になるように適宜調整されていればよい。なお、図３は、２ｎ＝３２個の、波長間隔１００ＧＨｚの光源を用いた上記構成により実現した多波長化光源の、最後の偏波合成器３０を通過する前のＣ点における光スペクトルである。
【００１７】
ところで、本発明原理による多波長化後の波長数は一般的に奇数となるのに対して、システム要求としては光源数を偶数倍化することが多い（例えば１００ＧＨｚ波長間隔の複数光源から１０ＧＨｚ，１２．５ＧＨｚまたは２５ＧＨｚ間隔のスペクトルを発生など）。このため、例えば奇数番目の光源の波長は（２Ｎ＋ｍ）倍化（Ｎは自然数，ｍは整数）し、偶数番目の光源の波長は（２Ｎ−ｍ）倍化するように変調器２７と２８の動作を調整してサイドモード光を発生させるのがよい。
【００１８】
ここで、図２（ａ）は、奇数番目の光源の波長を９倍化した例を示している。「９倍化」とは、矢印２３で示した光源波長の他に８つのサイドモード光、すなわち、併せて９波長の光パワーが所定の範囲内にあることを意味する。一方、図２（ｂ）の例は、偶数番目の光源について、矢印２４で示した光源波長の他に６つのサイドモード光（併せて７波長）の光パワーが所定の範囲内にある「７倍化」を示している。このように異なるスペクトル形状の多波長化された多重光を変調器２１，２２により生成し、偏波合成器３０により偏波合成することで、すべての波長の光パワーを偏差３．５ｄＢ以下（図３参照）とし、ほぼ均一とすることができる。
【００１９】
図４は、本実施形態の多波長光源において、多波長化された光源波長の一つ一つを分波器４０の波長分離フィルタで分離し、テスト信号で変調を施した上でその信号のＱ値を測定した結果を示している。
【００２０】
Ｑ値とは、受信波形の識別点を変化させて符号誤り率を測定し、この結果から一種の信号対雑音比を推定した値であり、Ｑ値が大きいほど信号対雑音比が大きく、したがって特性が良いことになる。図４において、光源波長４３と光源波長４４は（参照符号の添え字が）隣り合う光源のものであり、光源波長４３と光源波長４４のサイドモード光が合成されている波長においてもＱ値はそれぞれ良好な値を示しており、本実施形態によって干渉雑音等による劣化の無い信号変調が可能なことがわかる。
【００２１】
［第２実施形態］
図５は本発明に係る多波長光源の第２実施形態を示す構成図である。
本実施形態に係る多波長光源は、光源１０1〜１０2n、光合波器２１、光合波器２２、偏波合成器５０、変調器５５、および分波器４０から構成されている。図１中の構成要素と同一参照符号を付したものは同一構成であり、その説明を省略する。
【００２２】
本実施形態の多波長光源は、第１実施形態と比較して説明すると、変調器５５による多波長化の前に偏波合成器５０を用いて偏波合成する構成となっている。
【００２３】
これによると、変調器の個数を減らすことができ、第１実施形態よりもさらに簡単な構成とすることができる。しかし、変調器５５には、偏波無依存強度変調および位相変調器が要求される。
【００２４】
ところで、本実施形態の構成では、変調器５５においてそれぞれの光源１０1〜１０2nが発生するサイドモード光のスペクトル形状は、最後の偏波合成器３０を通過する前のＣ点における多波長化されたそれぞれの波長の光パワーがほぼ一定となるように調整されているとよい。
【００２５】
例えば、１００ＧＨｚ波長間隔の複数光源から、多波長化後のスペクトル間隔が１２．５ＧＨｚとなるように本構成によりサイドモード光を発生させる場合の調整例について、図６を参照して説明する。図６（ａ）〜（ｃ）はＣ点におけるスペクトルをそれぞれ示し、（ａ）は奇数番目光源によるもの、（ｂ）は偶数番目光源によるもの、（ｃ）は両者を併せて示している。
【００２６】
奇数番目光源によるものは、奇数番目光源の波長６１と６本のほぼ一定パワーのサイドモード光とこれらのほぼ半分のパワーのサイドモード光６１ａ，６１ｂ、および、別の奇数番目光源の波長６３と６本のほぼ一定パワーのサイドモード光とこれらのほぼ半分のパワーのサイドモード光６３ａ，６３ｂ，……を含む。一方、偶数番目光源によるものは、偶数番目光源の波長６２と６本のほぼ一定パワーのサイドモード光とこれらのほぼ半分のパワーのサイドモード光６２ａ，６２ｂ，……を含む。
【００２７】
このようなスペクトルが得られるように変調器５５の強度変調および位相変調動作を調整することで、最後の偏波合成器３０を通過する前のＣ点における分離前の光スペクトルを図６（ｃ）のようにほぼ一定とすることができる。
【００２８】
【発明の効果】
以上に述べたとおり、本発明に係る多波長光源によれば、強度変調および位相変調によるサイドモード光発生によって異なる波長の光を発生する複数の光源からの入力光を多波長化して複数の光キャリアを一括発生する際において、波長が隣り合う別の光源から発生した同一波長の２つのサイドモード光が互いに干渉して雑音を引き起こすことがなく、また、等間隔の波長グリッドに隙間のない多波長光源を、複雑な光回路の設計を行うこと無く、簡易かつ低コストな構成で提供することができ、これにより、光スペクトルの平坦化されたＷＤＭ信号を発生することができる。
【図面の簡単な説明】
【図１】本発明に係る多波長光源の第１実施形態を示す構成図である。
【図２】第１実施形態の多波長光源における偏波合成前の光スペクトルを奇数番目光源（ａ）と偶数番目光源（ｂ）について示す特性図である。
【図３】第１実施形態の多波長光源における偏波合成後の光スペクトルを示す特性図である。
【図４】第１実施形態の多波長光源によるＱ値を示す特性図である。
【図５】本発明に係る多波長光源の第２実施形態を示す構成図である。
【図６】第２実施形態の多波長光源における変調サイドモード光形状の例を説明する説明図である。
【符号の説明】
１０1〜１０2n 光源
２１，２２ 光合波器
２３，２４，４３，４４，６１〜６３ 光源波長
２７，２８，５５ 変調器
３０，５０ 偏波合成器
４０ 分波器（分離フィルタ）
６１a，６１ｂ，６２a，６２ｂ，６３a，６３ｂ 低（半分の）レベルのサイドモード光[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-wavelength light source, and more particularly to a multi-wavelength light source that is used in a wavelength division multiplexing communication system and collectively generates a plurality of optical carriers having different wavelengths from a plurality of input lights having different center wavelengths.
[0002]
[Prior art]
Conventionally, in optical communication, as a multi-wavelength simultaneous generation method having a flat optical spectrum used for wavelength division multiplexing (WDM), a flattened continuous optical spectrum obtained by supercontinuum generation by nonlinear optical fiber transmission is used as an optical signal. There are a method of cutting out by a filter and a method of transmitting an optical spectrum arranged on the frequency axis at a repetition frequency interval of an optical pulse obtained by generating an optical short pulse to an optical filter having a reverse frequency characteristic.
[0003]
[Problems to be solved by the invention]
However, in the flattening multi-wavelength generation method in Supercontinuum generation, there is a problem that it is not easy to manufacture a nonlinear optical fiber, and it takes time and cost. Also, in the flattening multi-wavelength generation method in which the optical spectrum obtained by the optical short pulse generation is transmitted through the inverse characteristic optical filter, in order to realize a flat optical spectrum, the duty of the optical short pulse and the corresponding light There was a problem that it was difficult to design the transmission characteristics of the filter.
[0004]
The present invention has been made in order to solve the above-described problems, and includes a simple and low-cost configuration without complicated optical circuit design, and a WDM signal with a flat optical spectrum accompanied by interference noise. An object of the present invention is to provide a multi-wavelength light source that can be generated in a lump.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 is a multi-wavelength light source that collectively generates a plurality of optical carriers having different wavelengths from a plurality of input lights each having a different center wavelength. First multiplexing means for multiplexing odd-numbered input light, second combining means for multiplexing even-numbered input light among the plurality of input lights, and the first combining means. The first modulation means for modulating the output light of the wave means to generate a predetermined side mode, and the modulation to generate the predetermined side mode for the output light of the second multiplexing means A second modulating means; a combining means for polarization combining the modulated outputs of the first and second modulating means; and a plurality of optical carriers having different wavelengths from the multi-wavelength combined output from the combining means Separation means for separating It was carried out multi-wavelength light source condition.
[0006]
According to a second aspect of the present invention, in the multi-wavelength light source according to the first aspect, the optical power of (2N + m) wavelengths (N is a natural number and m is an integer) is within a predetermined range at the output of the first modulation means. A side mode is generated, and the second modulation means generates a side mode so that the optical power of (2N−m) wavelengths (N is a natural number, m is an integer) is within a predetermined range at the output. A multi-wavelength light source of the form to implement was implemented.
[0007]
According to a third aspect of the present invention, there is provided a multi-wavelength light source that collectively generates a plurality of optical carriers having different wavelengths from a plurality of input lights each having a different central wavelength. First combining means for combining, second combining means for combining even-numbered input light among the plurality of input lights, and a combined output of the first combining means, A combining means for combining the polarization so that the polarization of the combined output of the second combining means is orthogonal; a modulating means for modulating and outputting the output light of the combining means in a predetermined spectral shape; and A multi-wavelength light source including a separating unit that separates a plurality of optical carriers having different wavelengths from an output modulated with multiple wavelengths is implemented.
[0008]
According to a fourth aspect of the present invention, in the multi-wavelength light source according to the first or third aspect, the first and second modulating means / the modulating means have respective output wavelengths at the outputs of the synthesizing means / the modulating means. A multi-wavelength light source is implemented that modulates so that the optical power is substantially constant and outputs a side mode.
[0009]
According to a fifth aspect of the present invention, in the multi-wavelength light source according to the fourth aspect, the modulation means is substantially in the middle of the adjacent input light wavelengths among the side modes of the output light corresponding to the plurality of adjacent input lights. The side mode is output so that the side mode between the input wavelength and the input optical wavelength has substantially constant optical power, and the side modes having the same wavelength and the intermediate wavelength are substantially half of the constant optical power. A multi-wavelength light source of the form to implement was implemented.
[0010]
[Action]
In the multi-wavelength light source according to the present invention configured as described above, two side mode lights having the same wavelength generated from light having adjacent wavelengths may cause interference noise because their polarizations are orthogonal to each other. Absent. For this reason, there is no deterioration at all wavelengths, and no gap is formed in the equally spaced wavelength grid.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
FIG. 1 is a block diagram showing a first embodiment of a multi-wavelength light source according to the present invention.
In the multi-wavelength light source according to the present embodiment, the input light from 2n (n is a natural number of 1 or more) light sources 10 1 to 10 2n that generate light having different single center wavelengths is divided into two systems. In this configuration, each modulation result is subjected to polarization synthesis and separated into a plurality of carriers having different wavelengths to obtain a final output. Hereinafter, this configuration and operation will be described in detail.
[0012]
In FIG. 1, for example, a distributed feedback (DFB) semiconductor laser or an external cavity semiconductor laser is used as the light sources 10 1 , 10 2 , 10 3 , 10 4 ,... 10 2n−1 , 10 2n . Each light source emits light at a single center wavelength, and each center wavelength is different, and they are arranged at equal intervals in the order of subscript numbers on the frequency axis.
[0013]
Reference numerals 21 and 22 denote optical multiplexers using, for example, an array type waveguide diffraction grating or an optical coupler. The optical multiplexer 21 multiplexes light from odd-numbered light sources. The optical multiplexer 22 multiplexes the light from each even-numbered light source independently of the optical multiplexer 21. The combined output from the optical combiner 21 is modulated by the modulator 27, the combined output from the optical combiner 22 is modulated by the modulator 28, and the modulators 27 and 28, for example, modulate the intensity and phase of the input combined light. More specifically, the modulation is performed. Specifically, one Mach-Zehnder type intensity modulator using lithium niobate as a medium and one phase modulator using lithium niobate as a medium are connected in series. it can.
[0014]
The output lights of both modulators 27 and 28 are combined by the polarization combiner 30 and then demultiplexed for each wavelength in the demultiplexer 40 configured by a separation filter, and a plurality of optical carriers having different wavelengths are generated in a lump. Is done.
[0015]
Here, FIG. 2A shows an enlarged part of an odd-numbered multi-wavelength optical spectrum generated by the modulator 27 at point A before polarization synthesis, and FIG. Fig. 5 shows an enlarged part of the even-numbered multi-wavelength optical spectrum at point B before polarization synthesis.
[0016]
As shown in both figures, the spectral shape of the side mode light by the modulator 27 (FIG. 2A) and the spectral shape of the side mode light by the modulator 28 (FIG. 2B) are not necessarily the same. . After polarization combining by the polarization beam combiner 30, the light power of all wavelengths may be adjusted as appropriate as shown in FIG. FIG. 3 shows an optical spectrum at point C before passing through the final polarization beam combiner 30 of the multi-wavelength light source realized by the above configuration using 2n = 32 light sources with a wavelength interval of 100 GHz. .
[0017]
By the way, the number of wavelengths after the multi-wavelength according to the principle of the present invention is generally an odd number, but as a system requirement, the number of light sources is often even-numbered (for example, from a plurality of light sources having a wavelength interval of 100 GHz to 10 GHz, Generate a spectrum at 12.5 GHz or 25 GHz intervals, etc.). Therefore, for example, the wavelengths of the odd-numbered light sources are multiplied by (2N + m) (N is a natural number, m is an integer), and the wavelengths of the even-numbered light sources are multiplied by (2N−m). It is preferable to adjust the operation to generate side mode light.
[0018]
Here, FIG. 2A shows an example in which the wavelength of the odd-numbered light source is multiplied by nine. “Nine times multiplication” means that in addition to the light source wavelength indicated by the arrow 23, eight side mode lights, that is, the optical power of nine wavelengths are within a predetermined range. On the other hand, in the example of FIG. 2B, for the even-numbered light source, the optical power of six side mode lights (7 wavelengths in addition to the light source wavelength indicated by the arrow 24) is within a predetermined range. "Double". In this way, multi-wavelength multiplexed light having different spectral shapes is generated by the modulators 21 and 22 and is combined by the polarization beam combiner 30 so that the optical power of all wavelengths is less than 3.5 dB in deviation ( 3) and can be made substantially uniform.
[0019]
FIG. 4 shows the multi-wavelength light source of the present embodiment, in which each of the multi-wavelength light source wavelengths is separated by the wavelength separation filter of the branching filter 40, modulated by a test signal, The result of measuring the Q value is shown.
[0020]
The Q value is a value obtained by measuring the code error rate by changing the discrimination point of the received waveform, and estimating a kind of signal-to-noise ratio from the result. The larger the Q value, the larger the signal-to-noise ratio. The characteristics will be good. In FIG. 4, the light source wavelength 43 and the light source wavelength 44 are those of adjacent light sources (subscripts of reference numerals), and the Q value is also obtained at the wavelength where the side mode light of the light source wavelength 43 and the light source wavelength 44 is synthesized. Each shows a good value, and it can be seen that the present embodiment can perform signal modulation without deterioration due to interference noise or the like.
[0021]
[Second Embodiment]
FIG. 5 is a block diagram showing a second embodiment of the multi-wavelength light source according to the present invention.
The multi-wavelength light source according to the present embodiment includes light sources 10 1 to 10 2n , an optical multiplexer 21, an optical multiplexer 22, a polarization beam combiner 50, a modulator 55, and a demultiplexer 40. Components having the same reference numerals as those in FIG. 1 have the same configuration, and a description thereof will be omitted.
[0022]
The multi-wavelength light source according to the present embodiment will be described in comparison with the first embodiment. The multi-wavelength light source is configured to synthesize polarization using the polarization synthesizer 50 before the multi-wavelength by the modulator 55.
[0023]
According to this, the number of modulators can be reduced, and the configuration can be further simplified as compared with the first embodiment. However, the modulator 55 requires a polarization independent intensity modulation and phase modulator.
[0024]
By the way, in the configuration of the present embodiment, the spectral shape of the side mode light generated by each of the light sources 10 1 to 10 2n in the modulator 55 is multi-wavelength at the point C before passing through the final polarization beam combiner 30. It is preferable that the optical power of each wavelength is adjusted so as to be substantially constant.
[0025]
For example, an adjustment example in the case where side mode light is generated by this configuration from a plurality of light sources having a wavelength interval of 100 GHz so that the spectral interval after multi-wavelength becomes 12.5 GHz will be described with reference to FIG. FIGS. 6 (a) to 6 (c) show the spectra at point C, respectively, (a) shows an odd-numbered light source, (b) shows an even-numbered light source, and (c) shows both.
[0026]
The odd-numbered light source has a wavelength 61 of the odd-numbered light source, six side mode lights having substantially constant power, side-mode lights 61a and 61b having almost half power, and a wavelength 63 of another odd-numbered light source. It includes six side mode lights with substantially constant power and side mode lights 63a, 63b,. On the other hand, the even-numbered light source includes the wavelength 62 of the even-numbered light source, six side mode lights with substantially constant power, and side mode lights 62a, 62b,.
[0027]
By adjusting the intensity modulation and phase modulation operations of the modulator 55 so as to obtain such a spectrum, the optical spectrum before separation at point C before passing through the final polarization beam combiner 30 is shown in FIG. ) As shown in FIG.
[0028]
【The invention's effect】
As described above, according to the multi-wavelength light source according to the present invention, the input light from a plurality of light sources that generate light of different wavelengths by generating side mode light by intensity modulation and phase modulation is converted into a plurality of wavelengths. When generating carriers all together, two side mode lights of the same wavelength generated from different light sources with adjacent wavelengths do not interfere with each other and cause noise, and there are many gaps in an equally spaced wavelength grid. The wavelength light source can be provided with a simple and low-cost configuration without designing a complicated optical circuit, thereby generating a WDM signal with a flat optical spectrum.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of a multi-wavelength light source according to the present invention.
FIG. 2 is a characteristic diagram showing an optical spectrum before polarization combining in the multi-wavelength light source of the first embodiment for an odd-numbered light source (a) and an even-numbered light source (b).
FIG. 3 is a characteristic diagram showing an optical spectrum after polarization combining in the multi-wavelength light source of the first embodiment.
FIG. 4 is a characteristic diagram showing a Q value by the multi-wavelength light source of the first embodiment.
FIG. 5 is a configuration diagram showing a second embodiment of a multi-wavelength light source according to the present invention.
FIG. 6 is an explanatory diagram illustrating an example of a modulated side mode light shape in the multi-wavelength light source of the second embodiment.
[Explanation of symbols]
10 1 to 10 2n light sources 21, 22 Optical multiplexers 23, 24, 43, 44, 61 to 63 Light source wavelengths 27, 28, 55 Modulator 30, 50 Polarization combiner 40 Demultiplexer (separation filter)
61a, 61b, 62a, 62b, 63a, 63b Low (half) level side mode light

Claims (5)

それぞれ異なる中心波長を有する複数の入力光から波長の異なる複数の光キャリアを一括発生する多波長光源において、
前記複数の入力光のうち、その波長が奇数番目の入力光を合波する第１合波手段と、
前記複数の入力光のうち、その波長が偶数番目の入力光を合波する第２合波手段と、
前記第１合波手段の出力光に対して所定のサイドモードを発生するように変調を行なう第１変調手段と、
前記第２合波手段の出力光に対して所定のサイドモードを発生するように変調を行なう第２変調手段と、
前記第１および第２の変調手段の変調出力を偏波合成する合成手段と、
前記合成手段からの多波長化されて合成された出力から前記波長の異なる複数の光キャリアを分離する分離手段と
を備えたことを特徴とする多波長光源。In a multi-wavelength light source that collectively generates a plurality of optical carriers having different wavelengths from a plurality of input lights having different center wavelengths,
A first multiplexing means for multiplexing the odd-numbered input light among the plurality of input lights;
A second multiplexing means for multiplexing the even-numbered input light among the plurality of input lights;
First modulation means for modulating the output light of the first multiplexing means so as to generate a predetermined side mode;
Second modulation means for modulating the output light of the second multiplexing means so as to generate a predetermined side mode;
Combining means for combining the modulated outputs of the first and second modulating means with polarization;
Separating means for separating a plurality of optical carriers having different wavelengths from the multi-wavelength synthesized output from the synthesizing means. 請求項１に記載の多波長光源において、
前記第１変調手段は、その出力において（２Ｎ＋ｍ）個の波長（Ｎは自然数，ｍは整数）の光パワーが所定範囲にあるようにサイドモードを発生し、
前記第２変調手段は、その出力において（２Ｎ−ｍ）個の波長（Ｎは自然数，ｍは整数）の光パワーが所定範囲にあるようにサイドモードを発生することを特徴とする多波長光源。The multi-wavelength light source according to claim 1,
The first modulation means generates a side mode so that the optical power of (2N + m) wavelengths (N is a natural number, m is an integer) is within a predetermined range at its output;
The second modulation means generates a side mode so that the optical power of (2N−m) wavelengths (N is a natural number, m is an integer) is within a predetermined range at the output thereof. . それぞれ異なる中心波長を有する複数の入力光から波長の異なる複数の光キャリアを一括発生する多波長光源において、
前記複数の入力光のうち、その波長が奇数番目の入力光を合波する第１合波手段と、
前記複数の入力光のうち、その波長が偶数番目の入力光を合波する第２合波手段と、
前記第１の合波手段の合波出力と第２の合波手段の合波出力の偏波が直交するように偏波合成する合成手段と、
前記合成手段の出力光を所定のスペクトル形状で変調出力する変調手段と、
前記変調手段からの多波長化されて変調された出力から前記波長の異なる複数の光キャリアを分離する分離手段と
を備えたことを特徴とする多波長光源。In a multi-wavelength light source that collectively generates a plurality of optical carriers having different wavelengths from a plurality of input lights having different central wavelengths,
A first multiplexing means for multiplexing the odd-numbered input light among the plurality of input lights;
A second multiplexing means for multiplexing the even-numbered input light among the plurality of input lights;
Combining means for combining the polarization so that the combined output of the first combining means and the combined output of the second combining means are orthogonal;
Modulation means for modulating and outputting the output light of the combining means in a predetermined spectral shape;
Separating means for separating a plurality of optical carriers having different wavelengths from the multi-wavelength modulated output from the modulating means. 請求項１または３に記載の多波長光源において、
前記第１および第２の変調手段／前記変調手段は、前記合成手段／前記変調手段の出力においてそれぞれの出力波長の光パワーがほぼ一定となるように調整してサイドモードを出力するように変調を行なうことを特徴とする多波長光源。The multi-wavelength light source according to claim 1 or 3,
The first and second modulation means / the modulation means modulate so that the optical power of each output wavelength is substantially constant at the output of the combining means / modulation means to output a side mode. A multi-wavelength light source. 請求項４に記載の多波長光源において、
前記変調手段は、隣り合う前記複数の入力光に応じた出力光のサイドモードのうち、当該隣り合う入力光波長のほぼ中間の波長と前記入力光波長の間のサイドモードがほぼ一定の光パワーとなり、互いに同一波長で、前記ほぼ中間の波長のサイドモードが前記一定の光パワーのほぼ半分となるようにサイドモードを出力することを特徴とする多波長光源。The multi-wavelength light source according to claim 4,
The modulating means has an optical power in which a side mode between the input light wavelengths and a wavelength substantially in the middle of the adjacent input light wavelengths is substantially constant among the output light side modes corresponding to the plurality of adjacent input lights. The multi-wavelength light source is characterized in that the side modes are output so that the side modes having the same wavelength and the substantially intermediate wavelength are approximately half of the constant optical power.
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CA002487181A CA2487181C (en) 2000-07-07 2001-07-05 Multi-wavelength generating method and apparatus based on flattening of optical spectrum
CA002352680A CA2352680C (en) 2000-07-07 2001-07-05 Multi-wavelength generating method and apparatus based on flattening of optical spectrum
CA002487187A CA2487187C (en) 2000-07-07 2001-07-05 Multi-wavelength generating method and apparatus based on flattening of optical spectrum
US09/900,613 US6831774B2 (en) 2000-07-07 2001-07-06 Multi-wavelength generating method and apparatus based on flattening of optical spectrum
US10/655,675 US6924924B2 (en) 2000-07-07 2003-09-04 Multi-wavelength generating method and apparatus based on flattening of optical spectrum
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