JP5279980B2 - Single mode optical fiber - Google Patents

Single mode optical fiber Download PDF

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JP5279980B2
JP5279980B2 JP2004002712A JP2004002712A JP5279980B2 JP 5279980 B2 JP5279980 B2 JP 5279980B2 JP 2004002712 A JP2004002712 A JP 2004002712A JP 2004002712 A JP2004002712 A JP 2004002712A JP 5279980 B2 JP5279980 B2 JP 5279980B2
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和秀 中島
泉 三川
健 周
千里 深井
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Nippon Telegraph and Telephone Corp
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本発明は広波長域における高速・大容量光通信に供する単一モード光ファイバに関する。   The present invention relates to a single-mode optical fiber used for high-speed and large-capacity optical communication in a wide wavelength range.

近年、1チャネル当たりの伝送速度の高速化と、波長分割多重(WDM:Wavelength Division multiplexing)技術の併用により、光ファイバ1心当たりの総伝送容量は飛躍的に拡大されている。WDM伝送では、多重波長領域における光ファイバの波長分散が低下すると、光ファイバ中の光非線形現象の1つである4光波混合の影響により、その伝送特性が著しく劣化するといった問題があった。   In recent years, the total transmission capacity per optical fiber has been dramatically increased by using a combination of a high transmission rate per channel and wavelength division multiplexing (WDM) technology. In the WDM transmission, when the chromatic dispersion of the optical fiber in the multiple wavelength region is lowered, there is a problem that the transmission characteristic is remarkably deteriorated due to the influence of four-wave mixing which is one of optical nonlinear phenomena in the optical fiber.

このため、特許文献1では、多重波長領域における単一モード光ファイバ波長分散を非零として設計する手法が提案されており、これまでに、様々な屈折率分布を有する非零分散シフトファイバが提案されている(例えば、特許文献2)。しかしながら、これら非零分散シフトファイバは波長1.55μm帯でのWDM伝送を想定して設計されているため、波長1.4μm帯、或いは波長1.6μm帯では新たに波長分散が審となる領域が発生し、1.55μm帯以外の波長領域におけるWDM伝送には不向きであるといった問題があった。   For this reason, Patent Document 1 proposes a method for designing non-zero single-mode optical fiber chromatic dispersion in a multi-wavelength region, and so far, non-zero dispersion shifted fibers having various refractive index distributions have been proposed. (For example, Patent Document 2). However, since these non-zero dispersion shifted fibers are designed for WDM transmission in the 1.55 μm wavelength band, a new area where chromatic dispersion is considered in the 1.4 μm wavelength band or 1.6 μm wavelength band. Occurs and is not suitable for WDM transmission in a wavelength region other than the 1.55 μm band.

このような問題に鑑み、1.4μm帯から1.6μm帯の広波長域において波長分散が非零となるように設計された光ファイバ、並びに低分散スロープ型の光ファイバも提案されている(例えば、特許文献3、非特許文献1及び2)。一方、1チャネル当たりの伝送速度が40Gbit/s以上となるような高速光伝送においては、約8ps/nm・km前後の中分散特性が望ましいことが報告されている(例えば、非特許文献3及び4)。   In view of such a problem, an optical fiber designed to have non-zero chromatic dispersion in a wide wavelength range from 1.4 μm band to 1.6 μm band and a low dispersion slope type optical fiber have also been proposed ( For example, Patent Document 3, Non-Patent Documents 1 and 2). On the other hand, in high-speed optical transmission in which the transmission rate per channel is 40 Gbit / s or more, it has been reported that medium dispersion characteristics around 8 ps / nm · km are desirable (for example, Non-Patent Document 3 and 4).

しかしながら、前記広波長域非零分散光ファイバ、或いは低分散スロープ型の光ファイバでは、必ずしも上述の好適な分散領域を満たしておらず、広波長域における高速WDM伝送の適用には不十分であるといった問題点があった。また、特に低分散スロープ型の光ファイバでは、分散スロープの低減とともに、実効断面積も減少する傾向にあり、同じく高速・長距離のWDM伝送には不向きとなるといった問題があった。
特開平7−168046 特開平11−223741 特表2002−526807 N. Kumano et al., "Zero dispersion-slope NZ-DSF with ultra wide bandwidth over 300 nm", ECOC2002, PD1.4, 2002. D. Molin et al., "Ultra-low slope medium-dispersion fiber for wide-band transmissions", OFC2003, TaB2, pp. 150- 151, 2003. B. Dany et al., "Optimization of 40Gbit/s dispersion maps for long-haul WDM transmission with up to 0.4bit/s/Hz spectral efficiency", OFC2001, TuN5, 2001. 中島他、“広波長域DWDM伝送用光ファイバの分散特性に関する考察”,2003年信ソ大,B13-2,2003. ITU-T、Recommendation G.652、 " Charactenstics of a smgle-mode optical fibre and cable"、表1/G.652、2OO3年3月版
However, the wide-wavelength non-zero dispersion optical fiber or the low-dispersion slope optical fiber does not necessarily satisfy the above-mentioned preferable dispersion region, and is insufficient for application of high-speed WDM transmission in a wide wavelength region. There was a problem. In particular, in the low dispersion slope type optical fiber, there is a tendency that the effective area is reduced as the dispersion slope is reduced, which is also unsuitable for high speed and long distance WDM transmission.
JP-A-7-168046 JP-A-11-223741 Special Table 2002-526807 N. Kumano et al., "Zero dispersion-slope NZ-DSF with ultra wide bandwidth over 300 nm", ECOC2002, PD1.4, 2002. D. Molin et al., "Ultra-low slope medium-dispersion fiber for wide-band transmissions", OFC2003, TaB2, pp. 150-151, 2003. B. Dany et al., "Optimization of 40Gbit / s dispersion maps for long-haul WDM transmission with up to 0.4bit / s / Hz spectral efficiency", OFC2001, TuN5, 2001. Nakajima et al., “Discussion on Dispersion Characteristics of Wide Wavelength DWDM Optical Fiber”, 2003 Shin-Sodai, B13-2, 2003. ITU-T, Recommendation G.652, "Charactenstics of a smgle-mode optical fiber and cable", Table 1 / G.652, 2OO3 March edition

本発明はこのような問題に鑑み、実用上有効な曲げ損失特性と、実効断面積と、遮断波長特性とを保持し、かつ波長1460nmから1625nmの広波長域で、高速WDM伝送に好適な分散特性を有する単一モード光ファイバを提案する。   In view of such problems, the present invention maintains a practically effective bending loss characteristic, effective cross-sectional area, and cutoff wavelength characteristic, and is a dispersion suitable for high-speed WDM transmission in a wide wavelength range from 1460 nm to 1625 nm. A single mode optical fiber with characteristics is proposed.

本発明では、屈折率の異なる2層から4層の構造により構成されるコア部と、クラッド部に配置された低屈折率層、或いは空孔部とを好適に設計し、波長1460nmから1625nmにおける波長分散特性を6ps/nm・kmから12ps/nm・kmの範囲内、波長1550nm、曲げ半径30mmにおける曲げ損失特性を20dB/km以下、波長1550nmにおける実効断面積を60μm2以上、理論遮断波長を1250nm以下とすることにより、上記課題を解決するための手段としている。 In the present invention, a core part constituted by a structure of two to four layers having different refractive indexes and a low refractive index layer or a hole part arranged in the clad part are suitably designed, and the wavelength is from 1460 nm to 1625 nm. Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km, bending loss characteristics at a wavelength of 1550 nm, bending radius of 30 mm, 20 dB / km or less, effective area at a wavelength of 1550 nm of 60 μm 2 or more, theoretical cutoff wavelength By setting the thickness to 1250 nm or less, the above-described problem is solved.

即ち、本発明の請求項1に係る単一モード光ファイバは、屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部と、クラッド部よりも屈折率の低い第2コア部と、前記クラッド部の領域内に配置されたクラッド部よりも屈折率の低い低屈折率層とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.32%であり、
かつ、第1コア部と第2コア部を合わせた全コア半径に対する、第1コア部の半径方向の比率が0.6、第1コア部のクラッド部に対する比屈折率差と第2コア部のクラッド部に対する比屈折率差との比率が−1.0であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記全コア半径に対する、コア中心からクラッド部に配置された低屈折率層の内周までの半径方向の規格化距離が2.5から3.8、低屈折率層の幅が9.0から9.1μm、第1コア部のクラッド部に対する比屈折率差と低屈折率層のクラッド部に対する比屈折率差との比率が−0.2であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする。
That is, the single mode optical fiber according to claim 1 of the present invention includes a clad portion having a uniform refractive index, a first core portion having a higher refractive index than the clad portion, and a second refractive index lower than that of the clad portion. In a single mode optical fiber comprising a core portion and a low refractive index layer having a refractive index lower than that of the cladding portion disposed in the region of the cladding portion, and having a theoretical cutoff wavelength characteristic of 1250 nm or less,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.32%;
The ratio of the first core portion in the radial direction to the total core radius of the first core portion and the second core portion is 0.6, the relative refractive index difference between the first core portion and the cladding portion and the second core portion. The total core radius is set so that the ratio of the relative refractive index difference with respect to the cladding portion is −1.0, and the chromatic dispersion at a wavelength of 1460 nm is 6 ps / nm · km,
The normalized distance in the radial direction from the center of the core to the inner periphery of the low refractive index layer disposed in the cladding portion with respect to the total core radius is 2.5 to 3.8 , and the width of the low refractive index layer is 9. 0 to 9.1 μm, the ratio of the relative refractive index difference with respect to the cladding portion of the first core portion and the relative refractive index difference with respect to the cladding portion of the low refractive index layer is −0.2,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm It has a cross-sectional area.

また、本発明の請求項2に係る単一モード光ファイバは、屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部及び第3コア部、並びにクラッド部よりも屈折率の低い第2コア部及び第4コア部と、前記クラッド部の領域内に配置されたクラッド部よりも屈折率の低い低屈折率層とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.33%であり、
かつ、第1コア部から第4コア部までを含む全コア半径に対する、第1コア部までの半径方向の比率が0.4、第2コア部までの半径方向の比率が0.7、第3コア部までの半径方向の比率が0.9、クラッド部を基準とした、第1コア部の比屈折率差と第2コア部の比屈折率差との比率が−1.0、第3コア部の比屈折率差との比率が0.5、第4コア部の比屈折率差との比率が−0.1であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記全コア半径に対する、コア中心からクラッド部に配置された低屈折率層の内周までの半径方向の規格化距離が1.4から2.8、低屈折率層の幅が7.8から8.2μm、第1コア部のクラッド部に対する比屈折率差と低屈折率層のクラッド部に対する比屈折率差との比率が−0.1であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする。
また、本発明の請求項3に係る単一モード光ファイバは、屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部及び第3コア部、並びにクラッド部よりも屈折率の低い第2コア部及び第4コア部と、前記クラッド部の領域内に配置されたクラッド部よりも屈折率の低い低屈折率層とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.33%であり、
かつ、第1コア部から第4コア部までを含む全コア半径に対する、第1コア部までの半径方向の比率が0.4、第2コア部までの半径方向の比率が0.7、第3コア部までの半径方向の比率が0.9、クラッド部を基準とした、第1コア部の比屈折率差と第2コア部の比屈折率差との比率が−1.0、第3コア部の比屈折率差との比率が0.5、第4コア部の比屈折率差との比率が−0.1であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記全コア半径に対する、コア中心からクラッド部に配置された低屈折率層の内周までの半径方向の規格化距離が1.5から3.0、低屈折率層の幅が4.0から4.1μm、第1コア部のクラッド部に対する比屈折率差と低屈折率層のクラッド部に対する比屈折率差との比率が−0.2であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする。
In addition, the single mode optical fiber according to claim 2 of the present invention has a clad portion having a uniform refractive index, a first core portion and a third core portion having a higher refractive index than the clad portion, and is refracted more than the clad portion. A second core portion and a fourth core portion having a low refractive index, and a low refractive index layer having a refractive index lower than that of the cladding portion disposed in the region of the cladding portion, and having a theoretical cutoff wavelength characteristic of 1250 nm or less. In single-mode optical fiber,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.33%;
And the ratio of the radial direction to the 1st core part with respect to all the core radii including from the 1st core part to the 4th core part is 0.4, the ratio of the radial direction to the 2nd core part is 0.7, The radial ratio up to 3 core parts is 0.9, the ratio of the relative refractive index difference of the first core part and the relative refractive index difference of the second core part with respect to the cladding part is -1.0, The ratio of the relative refractive index difference of the three core portions is 0.5, the ratio of the relative refractive index difference of the fourth core portion is −0.1, and the chromatic dispersion at the wavelength of 1460 nm is 6 ps / nm · km. The total core radius is set as
In addition, the normalized distance in the radial direction from the core center to the inner periphery of the low refractive index layer disposed in the clad portion with respect to the total core radius is 1.4 to 2.8, and the width of the low refractive index layer is 7. 8 to 8.2 μm, the ratio of the relative refractive index difference with respect to the cladding portion of the first core portion and the relative refractive index difference with respect to the cladding portion of the low refractive index layer is −0.1,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm It has a cross-sectional area.
In addition, the single mode optical fiber according to claim 3 of the present invention includes a clad part having a uniform refractive index, a first core part and a third core part having a refractive index higher than that of the clad part, and refracting more than the clad part. A second core portion and a fourth core portion having a low refractive index, and a low refractive index layer having a refractive index lower than that of the cladding portion disposed in the region of the cladding portion, and having a theoretical cutoff wavelength characteristic of 1250 nm or less. In single-mode optical fiber,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.33%;
And the ratio of the radial direction to the 1st core part with respect to all the core radii including from the 1st core part to the 4th core part is 0.4, the ratio of the radial direction to the 2nd core part is 0.7, The radial ratio up to 3 core parts is 0.9, the ratio of the relative refractive index difference of the first core part and the relative refractive index difference of the second core part with respect to the cladding part is -1.0, The ratio of the relative refractive index difference of the three core portions is 0.5, the ratio of the relative refractive index difference of the fourth core portion is −0.1, and the chromatic dispersion at the wavelength of 1460 nm is 6 ps / nm · km. The total core radius is set as
In addition, the normalized distance in the radial direction from the center of the core to the inner periphery of the low refractive index layer disposed in the cladding portion with respect to the total core radius is 1.5 to 3.0, and the width of the low refractive index layer is 4. 0 to 4.1 μm, the ratio of the relative refractive index difference with respect to the cladding portion of the first core portion and the relative refractive index difference with respect to the cladding portion of the low refractive index layer is −0.2,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm It has a cross-sectional area.

また、本発明の請求項に係る単一モード光ファイバは、屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部と、クラッド部よりも屈折率の低い第2コア部と、前記クラッド部の領域内にコア中心に対して同心円状の位置に配置された少なくとも4個以上の空孔部とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.32%であり、
かつ、第1コア部と第2コア部を合わせた全コア半径に対する、第1コア部の半径方向の比率が0.6、第1コア部のクラッド部に対する比屈折率差と第2コア部のクラッド部に対する比屈折率差との比率が−1.0であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記空孔部が、コア中心から、前記全コア半径の4倍から4.5倍離れたクラッド部に配置され、当該空孔部の、全コア半径に対する規格化半径が0.3倍以上であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする。
A single mode optical fiber according to a fourth aspect of the present invention includes a clad portion having a uniform refractive index, a first core portion having a higher refractive index than the clad portion, and a second refractive index lower than that of the clad portion. Single-mode optical fiber comprising a core portion and at least four or more hole portions arranged concentrically with respect to the core center in the region of the cladding portion, and having a theoretical cutoff wavelength characteristic of 1250 nm or less In
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.32 % ;
The ratio of the first core portion in the radial direction to the total core radius including the first core portion and the second core portion is 0.6 , and the relative refractive index difference between the first core portion and the clad portion is the second core portion. The total core radius is set so that the ratio of the relative refractive index difference with respect to the cladding portion is −1.0 , and the chromatic dispersion at a wavelength of 1460 nm is 6 ps / nm · km,
And the said void | hole part is arrange | positioned from the core center in the clad part 4 to 4.5 times away from the said all-core radius, and the normalization radius with respect to the all-core radius of the said void | hole part is 0.3 times That's it,
Chromatic dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths from 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and 60 μm 2 or more at a wavelength of 1550 nm It has an effective cross-sectional area.

また、本発明の請求項に係る単一モード光ファイバは、屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部及び第3コア部、並びにクラッド部よりも屈折率の低い第2コア部及び第4コア部と、前記クラッド部の領域内にコア中心に対して同心円状の位置に配置された少なくとも4個以上の空孔部とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.33%であり、
かつ、第1コア部から第4コア部までを含む全コア半径に対する、第1コア部までの半径方向の比率が0.4、第2コア部までの半径方向の比率が0.7、第3コア部までの半径方向の比率が0.9、クラッド部を基準とした、第1コア部の比屈折率差と第2コア部の比屈折率差との比率が−1.0、第3コア部の比屈折率差との比率が0.5、第4コア部の比屈折率差との比率が−0.1であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記空孔部が、コア中心から、前記全コア半径の3倍から3.5倍離れたクラッド部に配置され、当該空孔部の、全コア半径に対する規格化半径が0.2倍以上であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする。
In addition, the single mode optical fiber according to claim 5 of the present invention includes a clad portion having a uniform refractive index, a first core portion and a third core portion having a refractive index higher than that of the clad portion, and refracted more than the clad portion. The second core portion and the fourth core portion having a low rate, and at least four or more hole portions disposed concentrically with respect to the core center in the region of the cladding portion, and theoretical cutoff wavelength characteristics In a single mode optical fiber having a length of 1250 nm or less,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.33 % ;
In addition, the ratio of the radial direction to the first core part with respect to the total core radius including the first core part to the fourth core part is 0.4 , the ratio of the radial direction to the second core part is 0.7 , The ratio of the radial direction up to the three core parts is 0.9 , the ratio of the relative refractive index difference of the first core part and the relative refractive index difference of the second core part with respect to the cladding part is -1.0 , The ratio of the relative refractive index difference of the three core portions is 0.5 , the ratio of the relative refractive index difference of the fourth core portion is −0.1 , and the chromatic dispersion at the wavelength of 1460 nm is 6 ps / nm · km. The total core radius is set as
In addition, the hole is disposed in a clad part that is 3 to 3.5 times the total core radius from the core center, and the normalized radius of the hole with respect to the total core radius is 0.2 times That's it,
Chromatic dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths from 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and 60 μm 2 or more at a wavelength of 1550 nm It has an effective cross-sectional area.

本発明の単一モード光ファイバによれば、屈折率の異なる2層又は4層構造のコア部と、クラッド部に配置された低屈折率層、又は空孔部を好適に設計することにより、実用上有効な曲げ損失特性と、実効断面積と、理論遮断波長特性とを満たし、かつ波長1460nmから1625nmにおいて、WDM伝送に好適な6ps/nm・kmから12ps/nm・kmの波長分散特性を実現するといった効果を奏する。
また、本発明の単一モード光ファイバは、波長1625nm以下における波長分散が12ps/nm・km以下であるため、波長1625nm以下の信号光を用いる、伝送速度10Gbit/s、伝送距離100kmまでの伝送システムにおいて、伝送路の伝搬方向に累積する波長分散特性の補償を行うことなく、良好な伝送特性を実現できるといった効果も奏する。
According to the single mode optical fiber of the present invention, by suitably designing the core portion of the two-layer or four-layer structure having different refractive indexes and the low refractive index layer arranged in the cladding portion, or the hole portion, A chromatic dispersion characteristic of 6 ps / nm · km to 12 ps / nm · km that satisfies the practically effective bending loss characteristic, effective area, and theoretical cutoff wavelength characteristic, and is suitable for WDM transmission at wavelengths of 1460 nm to 1625 nm. The effect is achieved.
In addition, since the single mode optical fiber of the present invention has a chromatic dispersion of 12 ps / nm · km or less at a wavelength of 1625 nm or less, transmission using a signal light having a wavelength of 1625 nm or less and a transmission speed of 10 Gbit / s and a transmission distance of 100 km is performed. In the system, there is also an effect that good transmission characteristics can be realized without compensating for the chromatic dispersion characteristics accumulated in the propagation direction of the transmission path.

以下に本発明を実施するための最良の形態を実施例として図面に基づき説明する。   The best mode for carrying out the present invention will be described below as an embodiment with reference to the drawings.

本発明の第1実施例を図1に示す。
本実施例は、屈折率の異なる2層、又は4層の構造によるコア部と、クラッド部に低屈折率層を配置したものである。
図1は、単一モード光ファイバの断面方向の屈折率分布を表す概念図であり、図1(a)(b)は、それぞれコア部が2層、4層の屈折率層により構成される場合である。
また、以下の説明では、全コア半径aに対する第i(i=1,2,3)コア部の半径aiの比率をRai、第1コア部のクラッド部(SiO2)に対する比屈折率差Δ1と、第i(i=2,3,4)コア部のクラッド部に対する比屈折率差Δiとの比率をRΔiとして定義する。
A first embodiment of the present invention is shown in FIG.
In this embodiment, a core portion having a two-layer or four-layer structure having different refractive indexes and a low refractive index layer are arranged in the cladding portion.
FIG. 1 is a conceptual diagram showing a refractive index distribution in a cross-sectional direction of a single mode optical fiber. FIGS. 1A and 1B are each composed of two or four refractive index layers. Is the case.
In the following description, the ratio of the radius ai of the i-th (i = 1, 2, 3) core portion to the total core radius a is Rai, and the relative refractive index difference Δ1 with respect to the cladding portion (SiO 2 ) of the first core portion. And the ratio of the relative refractive index difference Δi to the clad portion of the i-th (i = 2, 3, 4) core portion is defined as RΔi.

また、コア中心から低屈折率層の内周までの距離をx、低屈折率層の幅をw、低屈折率層のクラッド部に対する比屈折率差をΔDとし、全コア半径aに対する、コア中心から低屈折率層の内周までの規格化距離をRaD、第1コア部の比屈折率差Δ1に対する低屈折率層の比屈折率差ΔDの比率をRΔDとして定義する。
尚、前記クラッド部(SiO2)に対する各コア部の比屈折率差Δi(i=1,2,3)、並びに低屈折率層の比屈折率差ΔDは、クラッド部の屈折率をn0、各コア部の屈折率をni、低屈折率層の屈折率をnDとして、次式(1)により定義する。
Further, the distance from the core center to the inner periphery of the low refractive index layer is x, the width of the low refractive index layer is w, the relative refractive index difference with respect to the cladding portion of the low refractive index layer is ΔD, and the core with respect to the total core radius a The standardized distance from the center to the inner periphery of the low refractive index layer is defined as RaD, and the ratio of the relative refractive index difference ΔD of the low refractive index layer to the relative refractive index difference Δ1 of the first core portion is defined as RΔD.
Note that the relative refractive index difference Δi (i = 1, 2, 3) of each core portion with respect to the cladding portion (SiO 2 ) and the relative refractive index difference ΔD of the low refractive index layer are n0, The refractive index of each core part is defined as ni, and the refractive index of the low refractive index layer is defined as nD, which is defined by the following formula (1).

Figure 0005279980
Figure 0005279980

図2は2層構造コアにおける、Ra1及びRΔ1に対する等波長分散特性の計算例を表すグラフである。図2(a)及び(b)は、それぞれ波長1550nm及び1625nmにおける等波長分散特性を表す。また、図2では第1コア部の比屈折率差Δ1、及び低屈折率層の比屈折率差ΔDを、それぞれ0.5%及び0%とし、波長1460nmの波長分散は6ps/nm・kmとして計算を行った。図2の計算例から、Ra1及びRΔ2を、それぞれ0.3〜0.75及び−0.5〜−1.4の範囲で最適化することにより、波長1625nmにおける波長分散を12ps/nm・km以下に設計できることが分かる。   FIG. 2 is a graph showing a calculation example of equal wavelength dispersion characteristics for Ra1 and RΔ1 in a two-layer structure core. FIGS. 2A and 2B show the equi-wavelength dispersion characteristics at wavelengths of 1550 nm and 1625 nm, respectively. In FIG. 2, the relative refractive index difference Δ1 of the first core portion and the relative refractive index difference ΔD of the low refractive index layer are 0.5% and 0%, respectively, and the chromatic dispersion at the wavelength of 1460 nm is 6 ps / nm · km. As a calculation. From the calculation example of FIG. 2, by optimizing Ra1 and RΔ2 in the range of 0.3 to 0.75 and −0.5 to −1.4, respectively, the chromatic dispersion at a wavelength of 1625 nm is 12 ps / nm · km. It can be seen that the following can be designed.

図3は2層構造コアにおける、比屈折率差Δ1と波長1550nmにおける実効断面積Aeffの関係の計算例を表すグラフである。尚、図の計算例ではRa1及びRΔ2を、それぞれ0.6及び−1.0、低屈折率層の比屈折率差ΔDを0%とした。図3より比屈折率差Δ1を0.32%以下とすることにより、60μm2以上の実効断面積が実現できることが分かる。
図4は2層構造コアにおける、コア中心から低屈折率層内周までの規格化距離RaDと低屈折率層の幅wに対する、波長1550nmにおける等曲げ損失特性(上図)、並びに波長1625nmにおける等波長分散特性(下図)の計算例を表すグラフである。尚、Ra1及びRΔ2は、それぞれ0.6及び−1.0、全コア半径a及び比屈折率差Δ1は、それぞれ6.5μm及び0.3%とし、低屈折率層のRΔDは−0.2とした。
FIG. 3 is a graph showing a calculation example of the relationship between the relative refractive index difference Δ1 and the effective area A eff at the wavelength of 1550 nm in the two-layer structure core. In the calculation example in the figure, Ra1 and RΔ2 are 0.6 and −1.0, respectively, and the relative refractive index difference ΔD of the low refractive index layer is 0%. It can be seen from FIG. 3 that an effective area of 60 μm 2 or more can be realized by setting the relative refractive index difference Δ1 to 0.32% or less.
FIG. 4 shows an equal bending loss characteristic (upper figure) at a wavelength of 1550 nm with respect to a normalized distance RaD from the center of the core to the inner periphery of the low refractive index layer and a width w of the low refractive index layer in the two-layer structure core, and at a wavelength of 1625 nm. It is a graph showing the example of calculation of an equal wavelength dispersion characteristic (the following figure). Ra1 and RΔ2 are 0.6 and −1.0, the total core radius a and the relative refractive index difference Δ1 are 6.5 μm and 0.3%, respectively, and RΔD of the low refractive index layer is −0. 2.

また同様に、図5は2層構造コアにおける、低屈折率層の規格化距離RaDと幅wに対する、波長1550nmにおける等曲げ損失特性(上図)、並びに波長1625nmにおける等波長分散特性(下図)の計算例を表すグラフであり、図4に対し、RΔDのみを−0.33に変更した計算例を表す。
図4並びに図5から、低屈折率層のRaD並びにwを、それぞれ2.5〜3.5並びに5.5μm〜9.5μmの範囲で最適化することにより、曲げ半径30mmにおける曲げ損失を10dB/km以下とし、かつ波長1625nmにおける波長分散を12ps/nm・km以下に設計できることが分かる。
Similarly, FIG. 5 shows an equal bending loss characteristic at a wavelength of 1550 nm (upper figure) and an equal wavelength dispersion characteristic at a wavelength of 1625 nm (lower figure) with respect to the normalized distance RaD and width w of the low refractive index layer in the two-layer structure core. FIG. 4 is a graph showing a calculation example in which only RΔD is changed to −0.33 with respect to FIG.
4 and FIG. 5, by optimizing RaD and w of the low refractive index layer in the range of 2.5 to 3.5 and 5.5 μm to 9.5 μm, respectively, the bending loss at a bending radius of 30 mm is 10 dB. It can be seen that the wavelength dispersion at a wavelength of 1625 nm can be designed to be 12 ps / nm · km or less.

ここで、非特許文献5によれば、現用の単一モード光ファイバにおける曲げ損失特性は、「曲げ半径30mm,100回巻きにおいて、損失増加0.50dB以下」と推奨されており、これは「曲げ半径30mmにおいて26.5dB/km以下の曲げ損失」に相当する。従って、前記、曲げ半径30mmにおける10dB/km以下の曲げ損失は、実用上十分な特性であると考えられる。
表1は上述の計算例に基づいて設計した、低屈折率層付与型の2層構造コア単一モード光ファイバにおける諸特性の計算結果を表す。表1から波長1460nmから1625nmにおける波長分散特性は6ps/nm・kmから12ps/nm・kmの範囲内であり、波長1550nm、曲げ半径30mmにおける20dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積と、1250nm以下の理論遮断波長特性が実現できることが分かる。
Here, according to Non-Patent Document 5, it is recommended that the bending loss characteristic in the current single mode optical fiber is “a loss increase of 0.50 dB or less at a bending radius of 30 mm and 100 turns”. This corresponds to a bending loss of 26.5 dB / km or less at a bending radius of 30 mm. Therefore, the bending loss of 10 dB / km or less at the bending radius of 30 mm is considered to be a practically sufficient characteristic.
Table 1 shows calculation results of various characteristics in the low-refractive-index layer-added two-layer core single-mode optical fiber designed based on the above calculation example. From Table 1, the chromatic dispersion characteristics at wavelengths from 1460 nm to 1625 nm are in the range of 6 ps / nm · km to 12 ps / nm · km, bending loss characteristics of 20 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and 60 μm at a wavelength of 1550 nm. It can be seen that an effective area of 2 or more and a theoretical cutoff wavelength characteristic of 1250 nm or less can be realized.

Figure 0005279980
Figure 0005279980

図6は、4層構造コアにおける、Ra2及びRa3に対する等波長分散特性の計算例を表すグラフである。図6(a)及び(b)は、それぞれ波長1550nm及び1625nmにおける等波長分散特性を表す。また、図6ではRa1=0.4,RΔ2=−1.0,RΔ3=0.5,RΔ4=−0.5とし、第1コア及び低屈折率層の比屈折率差を、それぞれ0.5%及び0%、波長1460nmの波長分散を6ps/nm・kmとした。図6から、Ra2及びRa3を、それぞれ0.6以上、及び0.7以上の領域で最適化することにより、波長1625nmにおける波長分散を12ps/nm・km以下に設計できることが分かる。   FIG. 6 is a graph showing a calculation example of equi-wavelength dispersion characteristics for Ra2 and Ra3 in a four-layer structure core. FIGS. 6A and 6B show the equal wavelength dispersion characteristics at wavelengths of 1550 nm and 1625 nm, respectively. In FIG. 6, Ra1 = 0.4, RΔ2 = −1.0, RΔ3 = 0.5, and RΔ4 = −0.5, and the relative refractive index difference between the first core and the low refractive index layer is 0. The chromatic dispersion at 5% and 0% and the wavelength of 1460 nm was 6 ps / nm · km. FIG. 6 shows that the chromatic dispersion at a wavelength of 1625 nm can be designed to be 12 ps / nm · km or less by optimizing Ra2 and Ra3 in the region of 0.6 or more and 0.7 or more, respectively.

図7は、4層構造コアにおける、RΔ2及びRΔ3に対する等波長分散特性の計算例を表すグラフである。図7(a)及び(b)は、それぞれ波長1550nm及び1625nmにおける等波長分散特性を表す。また、図7ではRa1=0.4,Ra2=0.7,Ra3=0.9,RΔ4=−0.1とし、第1コア及び低屈折率層の比屈折率差を、それぞれ0.5%及び0%、波長1460nmの波長分散を6ps/nm・kmとした。図7からRΔ2を−1.3〜−0.6の範囲で設計することにより波長1550nm及び波長1625nmにおける波長分散を6ps/nm・kmから12ps/nm・kmの範囲に設計できることが分かる。   FIG. 7 is a graph showing a calculation example of equi-wavelength dispersion characteristics for RΔ2 and RΔ3 in a four-layer structure core. FIGS. 7A and 7B show the equal wavelength dispersion characteristics at wavelengths of 1550 nm and 1625 nm, respectively. In FIG. 7, Ra1 = 0.4, Ra2 = 0.7, Ra3 = 0.9, RΔ4 = −0.1, and the relative refractive index difference between the first core and the low refractive index layer is 0.5. % And 0%, and the wavelength dispersion at a wavelength of 1460 nm was 6 ps / nm · km. It can be seen from FIG. 7 that the chromatic dispersion at the wavelength of 1550 nm and the wavelength of 1625 nm can be designed in the range of 6 ps / nm · km to 12 ps / nm · km by designing RΔ2 in the range of −1.3 to −0.6.

図8は、4層構造コアにおける、比屈折率差Δ1と波長1550nmにおける実効断面積Aeffの関係の計算例を表すグラフである。尚、Ra1,Ra2,Ra3,RΔ2,RΔ3、並びにRΔ4は、それぞれ0.4,0.7,0.9、−1.0,0.5、及び−0.1、低屈折率層の比屈折率差ΔDを0%とした。図8より、第1コアの比屈折率差Δ1を0.33%以下とすることにより、波長1550nmにおいて60μm2以上の実効断面積が得られることが分かる。 FIG. 8 is a graph showing a calculation example of the relationship between the relative refractive index difference Δ1 and the effective area A eff at the wavelength of 1550 nm in the four-layer structure core. Ra1, Ra2, Ra3, RΔ2, RΔ3, and RΔ4 are 0.4, 0.7, 0.9, -1.0, 0.5, and -0.1, respectively, and the ratio of the low refractive index layer. The refractive index difference ΔD was set to 0%. FIG. 8 shows that an effective area of 60 μm 2 or more can be obtained at a wavelength of 1550 nm by setting the relative refractive index difference Δ1 of the first core to 0.33% or less.

図9は、4層構造コアにおける、コア中心から低屈折率層内周までの規格化距離RaDと低屈折率層の幅wに対する、波長1550nmにおける等曲げ損失特性(上図)、並びに波長1625nmにおける等波長分散特性(下図)の計算例を表すグラフである。尚、Ra1,Ra2,Ra3,RΔ2,RΔ3、及びRΔ4は、それぞれ0.4,0.7,0.9、−1.0,0.5及び−0.1、全コア半径a及び比屈折率差Δ1は、それぞれ10.0μm及び0.3%とし、低屈折率層のRΔDは−0.1とした。   FIG. 9 shows an equal bending loss characteristic at a wavelength of 1550 nm (above) and a wavelength of 1625 nm with respect to the normalized distance RaD from the core center to the inner periphery of the low refractive index layer and the width w of the low refractive index layer in the four-layer structure core. It is a graph showing the example of a calculation of the equal wavelength dispersion characteristic (lower figure) in. Ra1, Ra2, Ra3, RΔ2, RΔ3, and RΔ4 are 0.4, 0.7, 0.9, -1.0, 0.5, and -0.1, the total core radius a, and the relative refraction, respectively. The rate difference Δ1 was 10.0 μm and 0.3%, respectively, and the RΔD of the low refractive index layer was −0.1.

また同様に、図10は4層構造コアにおける、低屈折率層の規格化距離RaDと幅wに対する、波長1550nmにおける等曲げ損失特性(上図)、並びに波長1625nmにおける等波長分散特性(下図)の計算例を表すグラフであり、図9に対し、RΔDのみを−0.2に変更した計算例を表す。図9並びに図10より、コア中心から低屈折率層内周までの規格化距離RaD、並びに低屈折率層の幅wを、それぞれ1.5〜2.5、並びに3.0〜9.0μmの範囲で最適化することにより、波長1625nmにおける波長分散を12ps/nm・km以下とし、かつ波長1550nmにおける曲げ半径30mmでの曲げ損失を10dB/km以下に設計できることが分かる。   Similarly, FIG. 10 shows an equal bending loss characteristic at a wavelength of 1550 nm (upper figure) and an equal wavelength dispersion characteristic at a wavelength of 1625 nm (lower figure) with respect to the normalized distance RaD and width w of the low refractive index layer in a four-layer structure core. FIG. 9 is a graph showing a calculation example of FIG. 9 and shows a calculation example in which only RΔD is changed to −0.2 with respect to FIG. 9 and 10, the normalized distance RaD from the core center to the inner periphery of the low refractive index layer and the width w of the low refractive index layer are 1.5 to 2.5 and 3.0 to 9.0 μm, respectively. By optimizing within the range, it can be seen that the chromatic dispersion at a wavelength of 1625 nm can be set to 12 ps / nm · km or less, and the bending loss at a bending radius of 30 mm at a wavelength of 1550 nm can be designed to be 10 dB / km or less.

表2は上述の計算例に基づいて設計した、低屈折率層付与型の4層構造コア単一モード光ファイバにおける諸特性の計算結果を表す。表2から波長1460nmから1625nmにおける波長分散特性は6ps/nm・kmから12ps/nm・kmの範囲内であり、波長1550nm、曲げ半径30mmにおける20dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積と、1250nm以下の理論遮断波長特性が実現できることが分かる。 Table 2 shows calculation results of various characteristics in a low refractive index layer-added type four-layer core single-mode optical fiber designed based on the above calculation example. From Table 2, the wavelength dispersion characteristics at wavelengths from 1460 nm to 1625 nm are in the range of 6 ps / nm · km to 12 ps / nm · km, the bending loss characteristic is 20 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and 60 μm at a wavelength of 1550 nm. It can be seen that an effective area of 2 or more and a theoretical cutoff wavelength characteristic of 1250 nm or less can be realized.

Figure 0005279980
Figure 0005279980

本発明の第2実施例を図11に示す。
本実施例は、屈折率の異なる2層又は4層の構造によるコア1と、クラッド部に6個の空孔2を配置したものである。
図11は、単一モード光ファイバの断面、並びにコア部の断面方向における屈折率分布を表す概念図であり、図11(a)(b)は、それぞれ2層、4層構造コア1の断面方向における屈折率分布を表している。
また、図11では1例として、クラッド部に6個の空孔2を配置した場合の断面図を示している。尚、以下の実施例の説明では、前述の第1実施例と同様に、第iコア部の断面方向における半径の比率をRai(i=1,2,3)、第1コアの比屈折率差に対する第iコア部の比屈折率差の比率をRΔi(i=2,3,4)とする。また、コア中心から空孔外周までの距離をx、空孔半径をrとし、全コア半径aに対する空孔外周までの規格化空孔距離をRaHとして定義する。
A second embodiment of the present invention is shown in FIG.
In the present embodiment, a core 1 having a two-layer or four-layer structure having different refractive indexes and six holes 2 are arranged in a clad portion.
FIG. 11 is a conceptual diagram showing a cross section of a single-mode optical fiber and a refractive index distribution in the cross-sectional direction of the core portion. FIGS. The refractive index distribution in the direction is represented.
In addition, FIG. 11 shows a cross-sectional view in the case where six holes 2 are arranged in the cladding as an example. In the following description of the embodiments, as in the first embodiment described above, the ratio of radii in the cross-sectional direction of the i-th core portion is Rai (i = 1, 2, 3), and the relative refractive index of the first core. The ratio of the relative refractive index difference of the i-th core part to the difference is RΔi (i = 2, 3, 4). Further, the distance from the core center to the hole outer periphery is defined as x, the hole radius is defined as r, and the standardized hole distance from the core periphery to the hole outer periphery is defined as RaH.

図12は、2層構造コアにおける、空孔外周までの規格化空孔距離RaHと、波長1550nm、曲げ半径30mmにおける曲げ損失特性の関係について、空孔半径rをパラメータとして計算を行った1例を示す。尚、図12の計算例では2層構造コア部のRa1を0.4,RΔ2を−1.0とし、全コア半径、並びに第1コアの比屈折率差Δ1を、それぞれ6.5μm並びに0.3%とした。図12より、規格化空孔距離RaH、並びに空孔半径rを、それぞれコア半径の4.5以下、並びに0.3倍以上に設定することにより、曲げ半径30mmにおける曲げ損失を20dB/km以下に低減できることが分かる。   FIG. 12 shows an example in which the relationship between the normalized hole distance RaH to the hole outer periphery and the bending loss characteristic at a wavelength of 1550 nm and a bending radius of 30 mm in the two-layer structure core is calculated using the hole radius r as a parameter. Indicates. In the calculation example of FIG. 12, Ra1 of the two-layer structure core portion is 0.4, RΔ2 is −1.0, the total core radius, and the relative refractive index difference Δ1 of the first core are 6.5 μm and 0, respectively. .3%. From FIG. 12, by setting the standardized hole distance RaH and the hole radius r to 4.5 cores or less and 0.3 times or more, the bending loss at a bending radius of 30 mm is 20 dB / km or less. It can be seen that it can be reduced.

図13は、2層構造コアにおける、規格化空孔距離RaHに対する、波長1550nmにおける実効断面積、並びに波長1625nmにおける波長分散特性に関する計算例を示す。尚、2層構造コア部のRa1は0.4,RΔ2は−1.0、全コア半径、並びに第1コアの比屈折率差は、それぞれ6.5μm、並びに0.3%とし、空孔半径は全コア半径の0.3倍とした。図12より、規格化空孔距離を全コア半径の4.0倍以上に設定することにより、波長1625nmにおける波長分散を12ps/nm・km以下とし、かつ空孔の付与に伴う実効断面積の減少を抑制できることが分かる。   FIG. 13 shows a calculation example regarding the effective cross-sectional area at a wavelength of 1550 nm and the chromatic dispersion characteristics at a wavelength of 1625 nm with respect to the normalized hole distance RaH in the two-layer structure core. Incidentally, Ra1 of the two-layer structure core portion is 0.4, RΔ2 is −1.0, the total core radius, and the relative refractive index difference of the first core are 6.5 μm and 0.3%, respectively. The radius was 0.3 times the total core radius. From FIG. 12, by setting the normalized hole distance to 4.0 times or more of the total core radius, the chromatic dispersion at a wavelength of 1625 nm is set to 12 ps / nm · km or less, and the effective cross-sectional area associated with the addition of holes is reduced. It can be seen that the decrease can be suppressed.

図14は、4層構造コアにおける、空孔外周までの規格化空孔距離RaHと、波長1550nm、曲げ半径30mmにおける曲げ損失特性の関係について、空孔半径rをパラメ一夕として計算を行った1例を示す。尚、図14の計算例では4層構造コア部のRa1,Ra2,Ra3,RΔ2,RΔ3、並びにRΔ4を、それぞれ0.4、0.7、0.9、−1.0、0.5及び−0.1とし、全コア半径を10.0μm、第1コアの比屈折率差を0.3%とした。図14より、規格化空孔距離RaH、並びに空孔半径rを、それぞれコア半径の3.5以下、並びに0.2倍以上に設定することにより、曲げ半径30mmにおける曲げ損失を20dB/km以下に低減できることが分かる。   FIG. 14 shows the relationship between the normalized hole distance RaH to the hole outer periphery and the bending loss characteristics at a wavelength of 1550 nm and a bending radius of 30 mm in the four-layer structure core, with the hole radius r being a parameter. An example is shown. In the calculation example of FIG. 14, Ra1, Ra2, Ra3, RΔ2, RΔ3, and RΔ4 of the four-layer structure core portion are set to 0.4, 0.7, 0.9, −1.0, 0.5, and 0.5, respectively. −0.1, the total core radius was 10.0 μm, and the relative refractive index difference of the first core was 0.3%. From FIG. 14, by setting the normalized hole distance RaH and the hole radius r to be 3.5 or less and 0.2 times or more of the core radius, the bending loss at a bending radius of 30 mm is 20 dB / km or less. It can be seen that it can be reduced.

図15は、4層構造コアにおける、規格化空孔距離RaHに対する、波長1550nmにおける実効断面積、並びに波長1625nmにおける波長分散特性に関する計算例を示す。尚、4層構造コア部のRa1,Ra2,Ra3,RΔ2,RΔ3、並びにRΔ4を、それぞれ0.4、0.7、0.9、−1.0、0.5及び−0.1とし、全コア半径を10.0μm、第1コアの比屈折率差を0.3%、空孔半径は全コア半径の0.2倍とした。図15より、規格化空孔距離を全コア半径の3.0倍以上に設定することにより、波長1625nmにおける波長分散を12ps/nm・km以下とし、かつ空孔の付与に伴う実効断面積の減少を抑制できることが分かる。   FIG. 15 shows a calculation example regarding the effective area at the wavelength of 1550 nm and the chromatic dispersion characteristic at the wavelength of 1625 nm with respect to the normalized pore distance RaH in the four-layer structure core. In addition, Ra1, Ra2, Ra3, RΔ2, RΔ3, and RΔ4 of the four-layer structure core portion are set to 0.4, 0.7, 0.9, −1.0, 0.5, and −0.1, respectively. The total core radius was 10.0 μm, the relative refractive index difference of the first core was 0.3%, and the hole radius was 0.2 times the total core radius. From FIG. 15, by setting the normalized hole distance to 3.0 times or more of the total core radius, the chromatic dispersion at a wavelength of 1625 nm is set to 12 ps / nm · km or less, and the effective cross-sectional area associated with the addition of holes is increased. It can be seen that the decrease can be suppressed.

表3は上述の第2実施例に基づいて設計した、空孔付与型の2層、並びに4層構造コア単一モード光ファイバにおける諸特性の計算結果を表す。表3から波長1460nmから1625nmにおける波長分散特性は6ps/nm・kmから12ps/nm・kmの範囲内であり、波長1550nm、曲げ半径30mmにおける20dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積と、1250nm以下の理論遮断波長特性が実現できることが分かる。 Table 3 shows calculation results of various characteristics in the hole-providing two-layer and four-layer core single-mode optical fibers designed based on the second embodiment described above. From Table 3, the wavelength dispersion characteristics at wavelengths from 1460 nm to 1625 nm are in the range of 6 ps / nm · km to 12 ps / nm · km, bending loss characteristics of 20 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and 60 μm at a wavelength of 1550 nm. It can be seen that an effective area of 2 or more and a theoretical cutoff wavelength characteristic of 1250 nm or less can be realized.

Figure 0005279980
Figure 0005279980

本発明は広波長域における高速・大容量光通信に供する単一モード光ファイバとして利用できるものである。   The present invention can be used as a single-mode optical fiber for high-speed and large-capacity optical communication in a wide wavelength range.

本発明の第1実施例に関する、光ファイバ断面方向の屈折率分布を表す概念図である。It is a conceptual diagram showing the refractive index distribution of the optical fiber cross section direction regarding 1st Example of this invention. 本発明の第1実施例に関し、2層構造コアにおける、Ra1及びRΔ1に対する等波長分散特性の計算例を表すグラフである。It is a graph showing the example of calculation of the equal wavelength dispersion characteristic with respect to Ra1 and Rdelta1 in a two-layer structure core regarding 1st Example of this invention. 本発明の第1実施例に関し、2層構造コアにおける、比屈折率差Δ1と実効断面積Aeffの関係の計算例を表すグラフである。It is a graph showing the example of calculation of the relationship between relative refractive index difference (DELTA) 1 and effective area Aeff in a 2 layer structure core regarding 1st Example of this invention. 本発明の第1実施例に関し、2層構造コアにおける、低屈折率層の規格化距離RaDと幅wに対する、等曲げ損失特性(上図)、並びに等波長分散特性(下図)の計算例を表すグラフである。(RΔD=−0.2)Regarding the first embodiment of the present invention, the calculation example of the equal bending loss characteristic (upper figure) and the equal wavelength dispersion characteristic (lower figure) with respect to the normalized distance RaD and the width w of the low refractive index layer in the two-layer structure core It is a graph to represent. (RΔD = −0.2) 本発明の第1実施例に関し、2層構造コアにおける、低屈折率層の規格化距離RaDと幅wに対する、等曲げ損失特性(上図)、並びに等波長分散特性(下図)の計算例を表すグラフである。(RΔD=−0.33)Regarding the first embodiment of the present invention, the calculation example of the equal bending loss characteristic (upper figure) and the equal wavelength dispersion characteristic (lower figure) with respect to the normalized distance RaD and the width w of the low refractive index layer in the two-layer structure core It is a graph to represent. (RΔD = −0.33) 本発明の第1実施例に関し、4層構造コアにおける、Ra2及びRa3に対する等波長分散特性の計算例を表すグラフである。It is a graph showing the example of calculation of the equal wavelength dispersion characteristic with respect to Ra2 and Ra3 in a 4-layer structure core regarding 1st Example of this invention. 本発明の第1実施例に関し、4層構造コアにおける、RΔ1及びRΔ2に対する等波長分散特性の計算例を表すグラフである。It is a graph showing the calculation example of the equal wavelength dispersion characteristic with respect to R (DELTA) 1 and R (DELTA) 2 in a 4 layer structure core regarding 1st Example of this invention. 本発明の第1実施例に関し、4層構造コアにおける、比屈折率差Δ1と波長1550nmにおける実効断面積Aeffの関係の計算例を表すグラフである。It is a graph showing the example of a calculation of the relationship between relative refractive index difference (DELTA) 1 and the effective area Aeff in wavelength 1550nm in 4 layer structure core regarding 1st Example of this invention. 本発明の第1実施例に関し、4層構造コアにおける、低屈折率層の規格化距離RaDと幅wに対する、等曲げ損失特性(上図)、並びに等波長分散特性(下図)の計算例を表すグラフである。(RΔD=−0.1)Regarding the first embodiment of the present invention, calculation examples of the equal bending loss characteristic (upper figure) and the equal wavelength dispersion characteristic (lower figure) with respect to the normalized distance RaD and width w of the low refractive index layer in the four-layer structure core It is a graph to represent. (RΔD = −0.1) 本発明の第1実施例に関し、4層構造コアにおける、低屈折率層の規格化距離RaDと幅wに対する、等曲げ損失特性(上図)、並びに等波長分散特性(下図)の計算例を表すグラフである。(RΔD=−0.2)Regarding the first embodiment of the present invention, calculation examples of the equal bending loss characteristic (upper figure) and the equal wavelength dispersion characteristic (lower figure) with respect to the normalized distance RaD and width w of the low refractive index layer in the four-layer structure core It is a graph to represent. (RΔD = −0.2) 本発明の第2実施例に関し、単一モード光ファイバの断面、並びにコア部の断面方向における屈折率分布を表す概念図である。It is a conceptual diagram showing the refractive index distribution in the cross section direction of the cross section of a single mode optical fiber, and a core part regarding 2nd Example of this invention. 本発明の第2実施例に関し、規格化空孔距離RaHと曲げ損失特性の関係の計算例を表すグラフである。It is a graph showing the example of calculation of the relationship between normalized hole distance RaH and a bending loss characteristic regarding 2nd Example of this invention. 本発明の第2実施例に関し、規格化空孔距離RaHに対する、実効断面積、波長分散特性に関する計算例を表すグラフである。It is a graph showing the example of a calculation regarding the effective area and wavelength dispersion characteristic with respect to 2nd Example of this invention with respect to normalized hole distance RaH. 本発明の第2実施例に関し、規格化空孔距離RaHと曲げ損失特性の関係の計算例を表すグラフである。It is a graph showing the example of calculation of the relationship between normalized hole distance RaH and a bending loss characteristic regarding 2nd Example of this invention. 本発明の第2実施例に関し、規格化空孔距離RaHに対する、実効断面積、波長分散特性に関する計算例を表すグラフである。It is a graph showing the example of a calculation regarding the effective area and wavelength dispersion characteristic with respect to 2nd Example of this invention with respect to normalized hole distance RaH.

符号の説明Explanation of symbols

1 コア
2 空孔
1 Core 2 Hole

Claims (5)

屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部と、クラッド部よりも屈折率の低い第2コア部と、前記クラッド部の領域内に配置されたクラッド部よりも屈折率の低い低屈折率層とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.32%であり、
かつ、第1コア部と第2コア部を合わせた全コア半径に対する、第1コア部の半径方向の比率が0.6、第1コア部のクラッド部に対する比屈折率差と第2コア部のクラッド部に対する比屈折率差との比率が−1.0であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記全コア半径に対する、コア中心からクラッド部に配置された低屈折率層の内周までの半径方向の規格化距離が2.5から3.8、低屈折率層の幅が9.0から9.1μm、第1コア部のクラッド部に対する比屈折率差と低屈折率層のクラッド部に対する比屈折率差との比率が−0.2であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする単一モード光ファイバ。
From a clad part having a uniform refractive index, a first core part having a higher refractive index than the clad part, a second core part having a lower refractive index than the clad part, and a clad part disposed in the region of the clad part In a single mode optical fiber comprising a low refractive index layer having a low refractive index and having a theoretical cutoff wavelength characteristic of 1250 nm or less,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.32%;
The ratio of the first core portion in the radial direction to the total core radius of the first core portion and the second core portion is 0.6, the relative refractive index difference between the first core portion and the cladding portion and the second core portion. The total core radius is set so that the ratio of the relative refractive index difference with respect to the cladding portion is −1.0, and the chromatic dispersion at a wavelength of 1460 nm is 6 ps / nm · km,
The normalized distance in the radial direction from the center of the core to the inner periphery of the low refractive index layer disposed in the cladding portion with respect to the total core radius is 2.5 to 3.8 , and the width of the low refractive index layer is 9. 0 to 9.1 μm, the ratio of the relative refractive index difference with respect to the cladding portion of the first core portion and the relative refractive index difference with respect to the cladding portion of the low refractive index layer is −0.2,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm A single-mode optical fiber having a cross-sectional area.
屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部及び第3コア部、並びにクラッド部よりも屈折率の低い第2コア部及び第4コア部と、前記クラッド部の領域内に配置されたクラッド部よりも屈折率の低い低屈折率層とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.33%であり、
かつ、第1コア部から第4コア部までを含む全コア半径に対する、第1コア部までの半径方向の比率が0.4、第2コア部までの半径方向の比率が0.7、第3コア部までの半径方向の比率が0.9、クラッド部を基準とした、第1コア部の比屈折率差と第2コア部の比屈折率差との比率が−1.0、第3コア部の比屈折率差との比率が0.5、第4コア部の比屈折率差との比率が−0.1であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記全コア半径に対する、コア中心からクラッド部に配置された低屈折率層の内周までの半径方向の規格化距離が1.4から2.8、低屈折率層の幅が7.8から8.2μm、第1コア部のクラッド部に対する比屈折率差と低屈折率層のクラッド部に対する比屈折率差との比率が−0.1であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする単一モード光ファイバ。
A clad part having a uniform refractive index, a first core part and a third core part having a higher refractive index than the clad part, a second core part and a fourth core part having a lower refractive index than the clad part, and the clad part In a single mode optical fiber comprising a low refractive index layer having a refractive index lower than that of the cladding portion disposed in the region, and having a theoretical cutoff wavelength characteristic of 1250 nm or less,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.33%;
And the ratio of the radial direction to the 1st core part with respect to all the core radii including from the 1st core part to the 4th core part is 0.4, the ratio of the radial direction to the 2nd core part is 0.7, The radial ratio up to 3 core parts is 0.9, the ratio of the relative refractive index difference of the first core part and the relative refractive index difference of the second core part with respect to the cladding part is -1.0, The ratio of the relative refractive index difference of the three core portions is 0.5, the ratio of the relative refractive index difference of the fourth core portion is −0.1, and the chromatic dispersion at the wavelength of 1460 nm is 6 ps / nm · km. The total core radius is set as
In addition, the normalized distance in the radial direction from the core center to the inner periphery of the low refractive index layer disposed in the clad portion with respect to the total core radius is 1.4 to 2.8, and the width of the low refractive index layer is 7. 8 to 8.2 μm, the ratio of the relative refractive index difference with respect to the cladding portion of the first core portion and the relative refractive index difference with respect to the cladding portion of the low refractive index layer is −0.1,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm A single-mode optical fiber having a cross-sectional area.
屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部及び第3コア部、並びにクラッド部よりも屈折率の低い第2コア部及び第4コア部と、前記クラッド部の領域内に配置されたクラッド部よりも屈折率の低い低屈折率層とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.33%であり、
かつ、第1コア部から第4コア部までを含む全コア半径に対する、第1コア部までの半径方向の比率が0.4、第2コア部までの半径方向の比率が0.7、第3コア部までの半径方向の比率が0.9、クラッド部を基準とした、第1コア部の比屈折率差と第2コア部の比屈折率差との比率が−1.0、第3コア部の比屈折率差との比率が0.5、第4コア部の比屈折率差との比率が−0.1であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記全コア半径に対する、コア中心からクラッド部に配置された低屈折率層の内周までの半径方向の規格化距離が1.5から3.0、低屈折率層の幅が4.0から4.1μm、第1コア部のクラッド部に対する比屈折率差と低屈折率層のクラッド部に対する比屈折率差との比率が−0.2であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする単一モード光ファイバ。
A clad part having a uniform refractive index, a first core part and a third core part having a higher refractive index than the clad part, a second core part and a fourth core part having a lower refractive index than the clad part, and the clad part In a single mode optical fiber comprising a low refractive index layer having a refractive index lower than that of the cladding portion disposed in the region, and having a theoretical cutoff wavelength characteristic of 1250 nm or less,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.33%;
And the ratio of the radial direction to the 1st core part with respect to all the core radii including from the 1st core part to the 4th core part is 0.4, the ratio of the radial direction to the 2nd core part is 0.7, The radial ratio up to 3 core parts is 0.9, the ratio of the relative refractive index difference of the first core part and the relative refractive index difference of the second core part with respect to the cladding part is -1.0, The ratio of the relative refractive index difference of the three core portions is 0.5, the ratio of the relative refractive index difference of the fourth core portion is −0.1, and the chromatic dispersion at the wavelength of 1460 nm is 6 ps / nm · km. The total core radius is set as
In addition, the normalized distance in the radial direction from the center of the core to the inner periphery of the low refractive index layer disposed in the cladding portion with respect to the total core radius is 1.5 to 3.0, and the width of the low refractive index layer is 4. 0 to 4.1 μm, the ratio of the relative refractive index difference with respect to the cladding portion of the first core portion and the relative refractive index difference with respect to the cladding portion of the low refractive index layer is −0.2,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm A single-mode optical fiber having a cross-sectional area.
屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部と、クラッド部よりも屈折率の低い第2コア部と、前記クラッド部の領域内にコア中心に対して同心円状の位置に配置された少なくとも4個以上の空孔部とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.32%であり、
かつ、第1コア部と第2コア部を合わせた全コア半径に対する、第1コア部の半径方向の比率が0.6、第1コア部のクラッド部に対する比屈折率差と第2コア部のクラッド部に対する比屈折率差との比率が−1.0であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記空孔部が、コア中心から、前記全コア半径の4倍から4.5倍離れたクラッド部に配置され、当該空孔部の、全コア半径に対する規格化半径が0.3倍以上であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする単一モード光ファイバ。
A clad part having a uniform refractive index, a first core part having a higher refractive index than the clad part, a second core part having a lower refractive index than the clad part, and a concentric circle with respect to the core center in the region of the clad part A single-mode optical fiber having at least four or more holes arranged in a shape and having a theoretical cutoff wavelength characteristic of 1250 nm or less,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.32%;
The ratio of the first core portion in the radial direction to the total core radius of the first core portion and the second core portion is 0.6, the relative refractive index difference between the first core portion and the cladding portion and the second core portion. The total core radius is set so that the ratio of the relative refractive index difference with respect to the cladding portion is −1.0, and the chromatic dispersion at a wavelength of 1460 nm is 6 ps / nm · km,
And the said void | hole part is arrange | positioned from the core center in the clad part 4 to 4.5 times away from the said all-core radius, and the normalization radius with respect to the all-core radius of the said void | hole part is 0.3 times That's it,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm A single-mode optical fiber having a cross-sectional area.
屈折率が均一なクラッド部と、クラッド部よりも屈折率の高い第1コア部及び第3コア部、並びにクラッド部よりも屈折率の低い第2コア部及び第4コア部と、前記クラッド部の領域内にコア中心に対して同心円状の位置に配置された少なくとも4個以上の空孔部とを備え、理論遮断波長特性を1250nm以下とする単一モード光ファイバにおいて、
第1コア部の前記クラッド部に対する比屈折率差が0.30から0.33%であり、
かつ、第1コア部から第4コア部までを含む全コア半径に対する、第1コア部までの半径方向の比率が0.4、第2コア部までの半径方向の比率が0.7、第3コア部までの半径方向の比率が0.9、クラッド部を基準とした、第1コア部の比屈折率差と第2コア部の比屈折率差との比率が−1.0、第3コア部の比屈折率差との比率が0.5、第4コア部の比屈折率差との比率が−0.1であって、波長1460nmにおける波長分散が6ps/nm・kmとなるように前記全コア半径が設定され、
かつ、前記空孔部が、コア中心から、前記全コア半径の3倍から3.5倍離れたクラッド部に配置され、当該空孔部の、全コア半径に対する規格化半径が0.2倍以上であり、
波長1460nmから1625nmにおいて6ps/nm・kmから12ps/nm・kmの範囲内の波長分散特性と、波長1550nm、曲げ半径30mmにおける10dB/km以下の曲げ損失特性と、波長1550nmにおける60μm2以上の実効断面積とを有することを特徴とする単一モード光ファイバ。
A clad part having a uniform refractive index, a first core part and a third core part having a higher refractive index than the clad part, a second core part and a fourth core part having a lower refractive index than the clad part, and the clad part In a single mode optical fiber having at least four or more holes disposed concentrically with respect to the center of the core in the region, and having a theoretical cutoff wavelength characteristic of 1250 nm or less,
A relative refractive index difference of the first core portion relative to the cladding portion is 0.30 to 0.33%;
And the ratio of the radial direction to the 1st core part with respect to all the core radii including from the 1st core part to the 4th core part is 0.4, the ratio of the radial direction to the 2nd core part is 0.7, The radial ratio up to 3 core parts is 0.9, the ratio of the relative refractive index difference of the first core part and the relative refractive index difference of the second core part with respect to the cladding part is -1.0, The ratio of the relative refractive index difference of the three core portions is 0.5, the ratio of the relative refractive index difference of the fourth core portion is −0.1, and the chromatic dispersion at the wavelength of 1460 nm is 6 ps / nm · km. The total core radius is set as
In addition, the hole is disposed in a clad part that is 3 to 3.5 times the total core radius from the core center, and the normalized radius of the hole with respect to the total core radius is 0.2 times That's it,
Wavelength dispersion characteristics in the range of 6 ps / nm · km to 12 ps / nm · km at wavelengths of 1460 nm to 1625 nm, bending loss characteristics of 10 dB / km or less at a wavelength of 1550 nm and a bending radius of 30 mm, and an effective value of 60 μm 2 or more at a wavelength of 1550 nm A single-mode optical fiber having a cross-sectional area.
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