JPS6243161B2 - - Google Patents
Info
- Publication number
- JPS6243161B2 JPS6243161B2 JP56001410A JP141081A JPS6243161B2 JP S6243161 B2 JPS6243161 B2 JP S6243161B2 JP 56001410 A JP56001410 A JP 56001410A JP 141081 A JP141081 A JP 141081A JP S6243161 B2 JPS6243161 B2 JP S6243161B2
- Authority
- JP
- Japan
- Prior art keywords
- wavelength
- light
- optical
- optical fiber
- transmission
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 230000005540 biological transmission Effects 0.000 claims description 25
- 239000013307 optical fiber Substances 0.000 claims description 22
- 230000003287 optical effect Effects 0.000 claims description 21
- 238000001069 Raman spectroscopy Methods 0.000 claims description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 10
- 239000006185 dispersion Substances 0.000 description 9
- 238000005086 pumping Methods 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 230000010355 oscillation Effects 0.000 description 3
- 239000004065 semiconductor Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- 230000000644 propagated effect Effects 0.000 description 1
- 230000001902 propagating effect Effects 0.000 description 1
- 230000008054 signal transmission Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2507—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion
- H04B10/2537—Arrangements specific to fibre transmission for the reduction or elimination of distortion or dispersion due to scattering processes, e.g. Raman or Brillouin scattering
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
- Optical Communication System (AREA)
Description
【発明の詳細な説明】
この発明は光フアイバ伝送方式において大きい
光信号を小さい伝送歪で伝送する光伝送方式に関
するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical fiber transmission system for transmitting large optical signals with small transmission distortion.
長距離、高帯域光伝送方式においては伝送路の
帯域制限の点から単一モード光フアイバが伝送路
として使用される。今、伝送容量1Gb／ｓ以上の
伝送方式を考えるとすると、光源としては半導体
レーザを用いた直接変調方式のPCM−IM（光強
度変調）方式が考えられる。一方、単一モード光
フアイバの伝送帯域はほゞ使用される光源の発振
波長拡がりΔλによつて決定される。すなわち波
長拡がりに起因するシリカ系単一モード光フアイ
バの構造分散と材料分散とで決まる波長分散は波
長1.5μｍ帯で約10ps／Km・ｎｍである。今、半
導体レーザの発振波長拡がりΔλを3nｍとする
と波長拡がりによる群遅延時間差Δτは約
30ps／Kmとなり、最大許容伝送速度ｆnをｆn＝
１／２Δτと定義すると、ｆnは約16Gb／ｓ・Km
となる。従つて1Gb／ｓの信号伝送に関しては伝
送帯域の面のみから考えると16Km伝送可能とな
る。 In long-distance, high-bandwidth optical transmission systems, single-mode optical fibers are used as transmission lines to limit the bandwidth of the transmission line. Now, when considering a transmission system with a transmission capacity of 1 Gb/s or more, a direct modulation type PCM-IM (light intensity modulation) system using a semiconductor laser as a light source can be considered. On the other hand, the transmission band of a single mode optical fiber is determined approximately by the oscillation wavelength spread Δλ of the light source used. That is, the wavelength dispersion determined by the structural dispersion and material dispersion of the silica-based single mode optical fiber caused by wavelength broadening is about 10 ps/Km·nm in the wavelength band of 1.5 μm. Now, if the oscillation wavelength spread Δλ of the semiconductor laser is 3 nm, the group delay time difference Δτ due to the wavelength spread is approximately
30 ps/Km, and the maximum allowable transmission speed f n is f n =
Defining 1/2Δτ, f n is approximately 16 Gb/s・Km
becomes. Therefore, in terms of 1 Gb/s signal transmission, it is possible to transmit a signal over 16 km, considering only the transmission band.
ところが半導体レーザの出力及び単一モード光
フアイバへの結合等を考慮すると現時点では１〜
５ｍＷの入力しか得られず、伝送路の損失等も考
慮すると高々１〜５Kmの中継スパンしか得られな
い。そこで光源から光フアイバへの入力パワを増
加させる事が考えられるが次のような理由で問題
がある。すなわち、何らかの光源で石英系単一モ
ード光フアイバに大きい光入力を与えると誘導ラ
マン散乱現象によつて入力光の発振波長とは異な
る光（ストークス光、アンチストークス光）が発
生し、そのため波長分散によつて伝送帯域が狭め
られる結果となる。第１図は長さ４Kmの石英系単
一モード光フアイバに波長1.06μｍ、出力20W、
パルス幅100nsecの光を入射させた場合の出力光
における波長に対する強度を表わしている。この
図からわかるように1.06μｍ以外の波長の光が伝
搬している。今簡単のため波長が1.06μｍの光以
外に600Å長波長の第１ストークス光のみが発生
して伝搬する場合の最大許容伝送速度ｆnを求め
ると、1.06μｍ帯での波長分散値を30ps／Km・ｎ
ｍとするとｆn＝278Mb／ｓKmとなり、1Gb／ｓ
の信号は１Kmすら伝送不可能となる。 However, considering the output of the semiconductor laser and the coupling to a single mode optical fiber, the current
Only an input of 5 mW can be obtained, and if transmission path losses are taken into consideration, a relay span of 1 to 5 km can be obtained at most. Therefore, increasing the input power from the light source to the optical fiber may be considered, but this poses a problem for the following reasons. In other words, when a large optical input is applied to a silica-based single mode optical fiber using some kind of light source, light (Stokes light, anti-Stokes light) different from the oscillation wavelength of the input light is generated due to the stimulated Raman scattering phenomenon, resulting in chromatic dispersion. This results in a narrowing of the transmission band. Figure 1 shows a 4 km long silica single mode optical fiber with a wavelength of 1.06 μm and an output of 20 W.
It represents the intensity versus wavelength of output light when light with a pulse width of 100 nsec is incident. As can be seen from this figure, light with wavelengths other than 1.06 μm is propagating. For the sake of simplicity, let us calculate the maximum allowable transmission speed f n when only the first Stokes light with a long wavelength of 600 Å is generated and propagated in addition to the light with a wavelength of 1.06 μm.The chromatic dispersion value in the 1.06 μm band is 30 ps/ Km・n
m, then f n =278Mb/sKm, which is 1Gb/s
The signal cannot be transmitted even 1 km.
誘導ラマン散乱は如何なる波長帯でも起り、か
つ光フアイバの損失が低減するにつれて増大す
る。したがつて、大きい光入力に対する伝送容
量、中継スパンの制限は誘導ラマン散乱による波
長分散によるものである。今、低損失光フアイバ
における入力光パワしきい値を、入力信号光と第
一次ストークス光とが等しくなる光パワとして定
義すると、損失が0.2dB／Kmで50Km程度の長尺の
光フアイバでは約500ｍＷとなり、大きい光パワ
を入力できないという欠点がある。 Stimulated Raman scattering occurs in any wavelength range and increases as optical fiber losses decrease. Therefore, limitations on transmission capacity and relay span for large optical inputs are due to wavelength dispersion due to stimulated Raman scattering. Now, if we define the input optical power threshold for a low-loss optical fiber as the optical power at which the input signal light and the first-order Stokes light are equal, then for a long optical fiber of about 50 km with a loss of 0.2 dB/Km, The output power is approximately 500mW, which has the disadvantage that large optical power cannot be input.
この発明はこれらの欠点を解決するため第一次
ストークス光が発生しないような構成とした光伝
送方式を提供するものである。 In order to solve these drawbacks, the present invention provides an optical transmission system configured to prevent the generation of first-order Stokes light.
この発明によれば使用光波長の損失係数、誘導
ラマン散乱における一次ストークス光波長での損
失係数、入力信号光パワ、伝送距離、光パワ閉じ
込め面積などを選定して第一次ストークス光が発
しないようにし、これにより高次のストークス光
の増大を押えて誘導ラマン散乱による波長分波を
無視できるようにする。このようにして大きな光
パワを入力し、かつ伝送帯域幅も広くすることが
できる。 According to this invention, the loss coefficient of the optical wavelength used, the loss coefficient at the primary Stokes optical wavelength in stimulated Raman scattering, the input signal optical power, the transmission distance, the optical power confinement area, etc. are selected to prevent primary Stokes light from being emitted. This suppresses the increase in higher-order Stokes light and makes it possible to ignore wavelength demultiplexing due to stimulated Raman scattering. In this way, it is possible to input large optical power and widen the transmission bandwidth.
単一モード光フアイバ中におけるポンピング光
（信号光）のパワＰpとストークス光のパワＰsiと
の関係は次式で表わされる。 The relationship between the power P p of pumping light (signal light) and the power P si of Stokes light in a single mode optical fiber is expressed by the following equation.
（ｄ／ｄＺ＋αp）Ｐp＝−ｇ０／ＡＰs1Ｐp (1)
（ｄ／ｄＺ＋αs1）Ｐs1＝ｇｓ１／Ａ（Ｐs1P0−Ｐs1Ｐ
s2）(2)
（ｄ／ｄＺ＋αs2）Ｐs2＝ｇｓ２／Ａ（Ｐs2Ｐs1−ＰS2
Ｐs3）(3)
〓
たゞし、αp及びαsiはそれぞれポンピング光
及び第ｉ次ストークス光の波長に対する減衰係
数、g0及びｇsiはそれぞれ単位面積当りのポンピ
ング光、及び第ｉ次ストークス光に対する増幅係
数Ａは光パワの集中している面積を、Ｚは距離を
それぞれ表わす。 (d/dZ+α p )P p =−g 0 /AP s1 P p (1) (d/dZ+α s1 )P s1 = g s1 /A(P s1 P 0 −P s1 P
s2 )(2) (d/dZ+α s2 )P s2 = g s2 /A(P s2 P s1 −P S2
P s3 )(3) 〓 Where, α p and α si are the attenuation coefficients for the wavelengths of the pumping light and the i-th Stokes light, respectively, g 0 and g si are the pumping light per unit area, and the i-th order Stokes light, respectively. The amplification coefficient A for Stokes light represents the area where the optical power is concentrated, and Z represents the distance.
(1)、(2)、(3)、………式からわかるように第２、
第３、………次ストークス光は第１次ストークス
光によつて増大する。したがつて第１次ストーク
ス光が増大しないようにすれば誘導ラマン散乱に
よる波長分散は無視できる。 (1), (2), (3),...As can be seen from the equation, the second
The third Stokes light is increased by the first Stokes light. Therefore, if the first-order Stokes light is prevented from increasing, wavelength dispersion due to stimulated Raman scattering can be ignored.
今、第１次ストークス光の増大が小さく、ポン
ピング光は吸収による減衰のみで変化すると仮定
すると、ポンピング光のパワＰp（Ｚ）は次のよ
うに近似できる。 Now, assuming that the increase in the first-order Stokes light is small and the pumping light changes only by attenuation due to absorption, the power P p (Z) of the pumping light can be approximated as follows.
Ｐp（Ｚ）＝Ｐp（０）exp（−αpＺ） (4)
（ｄ／ｄＺ＋αs1）Ｐs1（Ｚ）＝ｇ／ＡＰp（Ｚ）Ｐs1
（Ｚ）(5)
(4)、(5)式より第一次ストークス光のパワＰs1は
次式となる。 P p (Z)=P p (0)exp(-α p Z) (4) (d/dZ+α s1 )P s1 (Z)=g/AP p (Z)P s1
(Z)(5) From equations (4) and (5), the power P s1 of the first Stokes light is expressed as follows.
Ｐs1（Ｚ）＝Ｐs1（０）exp｛−αs1Ｚ＋ｇＰｐ（０）／αｐＡ〔１−exp（−αpＺ）〕｝ (6)
こゝで、αpＬ≫１の場合には(6)式は次のよう
に簡単化される。 P s1 (Z)=P s1 (0)exp{-α s1 Z+gP p (0)/α p A[1-exp(-α p Z)]} (6) Here, α p L≫1 In this case, equation (6) can be simplified as follows.
Ｐs1（Ｌ）＝Ｐs1（０）exp〔−αs1Ｌ＋ｇＰｐ（０）／αｐＡ (7)
(7)式より、第１次ストークス光の距離Ｌにおけ
るパワＰs1（Ｌ）が距離ゼロにおけるパワＰs1
（０）より増大しない条件は次式で求まる。 P s1 (L)=P s1 (0) exp [−α s1 L+gP p (0)/α p A (7) From equation (7), the power P s1 (L) at the distance L of the first Stokes light is Power at zero distance P s1
The condition for not increasing more than (0) can be found by the following equation.
αs1≧ｇＰｐ（０）／ＬαｐＡ (8)
したがつて(8)式を満足させるように第一次スト
ークス光波長での減衰係数を持つた光フアイバを
伝送路として使用すれば誘導ラマン散乱による波
長分散制限を受けることなく、大きい入力パワを
伝送することができる。 α s1 ≧gP p (0)/Lα p A (8) Therefore, if an optical fiber with an attenuation coefficient at the first Stokes wavelength that satisfies equation (8) is used as a transmission line, the guiding Large input power can be transmitted without being limited by chromatic dispersion due to Raman scattering.
今、シリカ系光フアイバでの(8)式を見積もると
次のようになる。 Now, estimating equation (8) for a silica-based optical fiber yields the following.
ｇ＝9.2×10-14ｍ／Ｗ
αp＝1dB／Km＝2.3×10-4ｍ-1
Ａ＝25μｍ２＝2.5×10-11ｍ２
Ｐp（０）＝10W
Ｌ＝50Km
上記パラメータでの第１次ストークス光の波長
に対する減衰係数αs1は13.9dB／Kmとなる。こゝ
で第一次ストークス光の波長シフトは通常450cm
-1であるため1.3μｍ帯での波長シフトは約760Å
となる。 g=9.2× 10-14 m/W α p =1dB/Km=2.3× 10-4 m -1 A=25μm 2 =2.5× 10-11 m2 P p (0)=10W L =50Km With the above parameters The attenuation coefficient α s1 for the wavelength of the first-order Stokes light is 13.9 dB/Km. Here, the wavelength shift of the first Stokes light is usually 450 cm.
-1 , so the wavelength shift in the 1.3μm band is approximately 760Å
becomes.
第２図はシリカ系単一モード光フアイバの損失
−波長特性である。（文献、研究実用化報告第28
巻第６号PP955−962、1979）、第２図におけるＡ
点（波長約1.3μｍ）での損失係数は約3dB／
Km、Ａ点から約760Å長波長側のＢ点での損失係
数は20dB／Km以上であるため(8)式の条件をを満
足している。 FIG. 2 shows the loss-wavelength characteristics of a silica-based single mode optical fiber. (Literature, Research and Practical Application Report No. 28
Volume 6 No. PP955-962, 1979), A in Figure 2
The loss coefficient at the point (wavelength approximately 1.3μm) is approximately 3dB/
Km, the loss coefficient at point B on the longer wavelength side of about 760 Å from point A is 20 dB/Km or more, so the condition of equation (8) is satisfied.
すなわち、Ａ点での波長を信号光として使用す
れば大きい光入力に対しても誘導ラマン散乱は起
らず長距離、広帯域伝送が可能となる。 That is, if the wavelength at point A is used as the signal light, stimulated Raman scattering does not occur even with a large optical input, and long-distance, broadband transmission becomes possible.
また光フアイバを製造する段階である波長に対
して大きい損失を与えるように設計することは可
能である。またある波長のみ結合させ損失を与え
る構造とした光フアイバにおいても同様の効果を
得ることができる。 Furthermore, it is possible to design an optical fiber to give a large loss to a certain wavelength at the stage of manufacturing the optical fiber. A similar effect can also be obtained with an optical fiber having a structure in which only a certain wavelength is coupled and loss is caused.
以上説明したようにこの発明の光伝送方式では
ストークス光が増大しないため、波長分散による
帯域制限がなく、更に大きい入力パワを伝送する
ことができるため長距離、広帯域伝送が可能とな
る利点がある。 As explained above, in the optical transmission system of the present invention, Stokes light does not increase, so there is no band limitation due to chromatic dispersion, and even greater input power can be transmitted, which has the advantage of enabling long-distance, broadband transmission. .
第１図は単一モード光フアイバにおける誘導ラ
マン散乱特性の一例を示す図、第２図は単一モー
ド光フアイバの損失−波長特性の一例を示す図で
ある。
Ａ点：信号光の波長、Ｂ点：第一次ストークス
光の波長。
FIG. 1 is a diagram showing an example of stimulated Raman scattering characteristics in a single mode optical fiber, and FIG. 2 is a diagram showing an example of loss-wavelength characteristics of the single mode optical fiber. Point A: wavelength of signal light, point B: wavelength of first-order Stokes light.
Claims (1)
において、伝送信号光波長での損失係数αp、誘
導ラマン散乱における１次ストークス光波長での
損失係数αsが αs≧ｇＰｐ（０）／ＬαｐＡ （たゞしｇはラマンゲイン、Ｐp（０）は入力信号
光パワ、Ｌは伝送距離、Ａは光パワ閉じ込め面
積）を満足するように構成した光フアイバを用い
て信号光を伝送することを特徴としたハイパワ光
伝送方式。[Claims] 1. In an optical transmission system using a single mode optical fiber, the loss coefficient α p at the wavelength of the transmission signal light and the loss coefficient α s at the first-order Stokes light wavelength in stimulated Raman scattering satisfy α s ≧ An optical fiber configured to satisfy gP p (0)/Lα p A (where g is Raman gain, P p (0) is input signal optical power, L is transmission distance, and A is optical power confinement area) is A high-power optical transmission system characterized by the use of optical signals to transmit signal light.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56001410A JPS57115042A (en) | 1981-01-08 | 1981-01-08 | High power optical transmission system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP56001410A JPS57115042A (en) | 1981-01-08 | 1981-01-08 | High power optical transmission system |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS57115042A JPS57115042A (en) | 1982-07-17 |
| JPS6243161B2 true JPS6243161B2 (en) | 1987-09-11 |
Family
ID=11500711
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP56001410A Granted JPS57115042A (en) | 1981-01-08 | 1981-01-08 | High power optical transmission system |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS57115042A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5508845A (en) * | 1990-10-18 | 1996-04-16 | Telstra Corporation Limited | Quasi-soliton communication system |
| US5303318A (en) * | 1991-11-01 | 1994-04-12 | Nippon Telegraph & Telephone Corporation | High power acceptable optical fiber and fabrication method thereof |
| GB9315231D0 (en) * | 1993-07-22 | 1993-09-08 | York Ltd | Optical time domain reflextometry |
-
1981
- 1981-01-08 JP JP56001410A patent/JPS57115042A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS57115042A (en) | 1982-07-17 |
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