KR100622615B1 - Optical fiber having low non-linearity for wdm transmission - Google Patents

Abstract

The optical transmission fiber has a refractive index distribution having an increased refractive index area in the inner core of the optical transmission fiber, an annular region located radially outward from the inner core with an index of refraction exceeding the index of refraction of the inner core, and an annular range with the inner core. It has at least a low dopant component region in the cross-sectional area in between. A low loss clad layer surrounds the core region. Light transmission fibers with divided core distributions provide high effective cross-sectional areas, low non-linear coefficients, nonzero dispersion, and relatively flat planar dispersion slopes.

Description

OPTICAL FIBER HAVING LOW NON-LINEARITY FOR WDM TRANSMISSION}

1 is a cross-sectional view of a transmission fiber according to the present invention.

2 is a graph of refractive index distribution of a cross-sectional view of the fiber of FIG. 1 according to a first embodiment of the present invention.

3 is a computer simulation graph of variance versus inner core radius for a first embodiment of the present invention.

4 is a computer simulation graph of the refractive index distribution area versus the effective cross-sectional area of the inner core for the first embodiment of the present invention.

의 컴퓨터 시뮬레이션 그래프다.Figure 5 shows the internal peak area vs. non-linear coefficient of the first embodiment of the present invention.

A computer simulation graph of.

6 is a computer simulation graph of refractive index distribution versus effective cross-sectional area for a second glass layer in a first embodiment of the present invention.

7 is a computer simulated graph of optical fiber radius versus electric field in a first embodiment of the present invention.

8A is a computer simulation graph of effective cross-sectional area versus non-linear coefficients in a first embodiment of the present invention.

8B is a computer simulation of non-linear coefficients versus effective cross-sectional area for a conventional dual shaped distributed shift optical fiber.

9 is a graph of refractive index distribution of a cross-sectional view of the fiber shown in FIG. 1 which is the same as the second embodiment of the present invention.

10 is a graph of refractive index distribution of a cross-sectional view of the fiber shown in FIG. 1 which is the same as the third embodiment of the present invention.

11 is a refractive index distribution diagram of the fibers in FIG. 1 which are the same as in the fourth embodiment of the present invention.

12 is a graph of wavelength versus total dispersion for a fiber according to a fourth embodiment of the present invention.

FIG. 13 is a refractive index distribution diagram of the fiber in FIG. 1 which is the same as the fifth embodiment of the present invention. FIG.

FIELD OF THE INVENTION The present invention generally relates to light transmission fibers having improved characteristics that reduce non-linear effects, and more particularly, where the maximum refractive index difference consists of two refractive index peaks located in the outer core region. The present invention relates to optical fibers used in wavelength-division-multiplexing (hereinafter referred to as WDM).

In optical communication systems, non-linear light effects are known to degrade the quality of transmission along standard transmission optical fibers in certain situations. Four-wave mixing (FWM), self-phase modulation (SPM), cross-phase modulation (XOM), modulation instability (MI), induction The non-linear effects, including stimulated brillouin scattering (SBS) and stimulated Raman scattering (SRS), produce distortion in high power systems.

및 파워 P의 곱과 관련이 있다. 아이이이이 저널 오브 퀀텀 일렉트로닉스 QE-23, NO. 5,1987에 기재된 와이 코다마 등에 의한 논문 "단일모드 유전체 가이드에서의 비-선형 펄스 전파"("Nonlinear pulse propagation in a monomode dielectric guide" Y. Kodama et al., IEEE Journal of Quantum Electronics, vol. QE-23, No. 5, 1987)내에서 주어진 것처럼 비-선형 계수

의 정의는 다음과 같다.The intensity of the non-linear effect along the pulse propagation in the optical fiber is a non-linear coefficient

And power P. IEI Journal of Quantum Electronics QE-23, NO. "Nonlinear pulse propagation in a monomode dielectric guide" by Y. Kodama et al., Y. Kodama et al., IEEE Journal of Quantum Electronics, vol. QE. -23, No. 5, 1987) as a non-linear coefficient

The definition of is as follows.

Where r is the radial coordinate of the fiber, n _eff is the effective mode refractive index, λ is the signal wavelength, n (r) is the refractive index radial distribution, n ₂ (r) is the non-linear exponential radial distribution, and F (r ) Is the basic mode radial distribution.

Applicants have taken into account the radial dependence of the non-linear index coefficient n ₂ by various concentrations of the fiber dopant used by Equation (1) to raise (or lower) the refractive index for pure silica. Confirmed.

에 대한 일반적으로 사용되는 수식을 얻을 수 있다.If you ignore the radial dependence of the non-linear exponent coefficient n ₂ , the coefficient

You can get commonly used formulas for.

Here, the following so-called effective core areas, i.e., the effective cross-sectional area, were introduced.

값을 갖는 굴절률 방사상 특성간을 식별하지 못했다. 1/A_eff가 종종 전송 섬유내의 비-선형 효과의 강도의 측정치로서 사용되는 반면에, 상기 수식(1)으로 정의되는 바와 같이

는 상기 효과의 강도의 보다 정확한 측정치를 제공한다.In contrast to the definition (1) above, the opposite approximation (2) has the same effective core area A _eff but different

It was not possible to distinguish between refractive index radial properties with values. While 1 / A _eff is often used as a measure of the strength of the non-linear effect in the transmission fiber, as defined by Equation (1) above

Provides a more accurate measure of the strength of the effect.

Group velocity dispersion also limits the transmission quality of optical signals over long distances. Group velocity dispersion widens the optical pulse during transmission over long distances, and the extended optical pulse can derive the dispersion of optical energy outside the time slot assigned to the pulse. Dispersion of light pulses can be slightly avoided by reducing the spacing between regenerators in the transmission system, but this approach is expensive and difficult to take advantage of repeaterless optical amplification.

One method of interactive dispersion is to add a suitable dispersion compensation system, such as a grating or dispersion compensation fiber, to the communication system.

In addition, one trend in optical communications to compensate for dispersion is a non-linear phenomenon of self-phase modulation with a specific form of return to zero (RZ) that maintains pulse width over long distances by balancing the effects of group velocity dispersion. It is to use the soliton pulse which is a modulation signal. The basic equation governing soliton propagation in single mode fiber is as follows.

은 이전에 언급한 광섬유 비-선형 계수이다. 상기 수식(4)의 만족은 펄스가 전파하는 동안 솔리톤 상태에 유지되기 위해 필요하다.P ₀ is the peak power of the soliton pulse, T ₀ is the duration of the pulse, D is the total variance, λ is the center wavelength of the soliton signal,

Is the previously mentioned optical fiber non-linear coefficient. Satisfaction of Equation (4) is necessary to remain in the soliton state during pulse propagation.

The problem that can occur in the transmission of the same soliton as in Equation (4) is that the conventional optical transmission fiber is lossy and this exponentially reduces the peak power P ₀ of the soliton pulse according to the total length of the optical fiber between the optical amplifiers. To compensate for this reduction, the peak power P ₀ of the soliton pulse can be set to a value sufficient to compensate for the substantial reduction in power along the transmission line at its firing point. F. M. Nax et al., WeC 3.2, p. 3, 101-104, ECOC 1996 Oslo (Norway) (FM Knox et al., Paper WeC. 3.2, page 3. 101-104, ECOC'96, Oslo (Norway)). Another attempt, as disclosed, is to use dispersion compensation fibers to compensate for dispersion accumulated by the pulses over the full length of the transmission line where the peak power of the pulses is under soliton propagation conditions, although dispersion fiber is also used.

의 값을 갖는 광섬유의 필요를 제안하였다.Non-return-to-zero NRZ optically amplified WDM systems, and low non-linear effects to avoid or limit non-linear effects as previously described for use in transmission systems such as non-amplified systems. Optical fibers with linear modulus are preferred. In addition, optical fibers with low non-linear coefficients enable an increase in firing power while maintaining a non-linear effect at the same level. Increased firing power also means the possibility of reaching a better S / N ratio (lower BER), and / or longer transmission distance in the receiver by increasing the amplifier spacing. Therefore, Applicant has a low non-linear coefficient

A need for an optical fiber having a value of is proposed.

도 이에 따라 증가해야한다는 것을 의미한다. 그러므로, 비-선형 계수

의 보다 낮은 값은 솔리톤 전송 시스템에서 라인 증폭기 사이의 증가한 거리를 제공하기 위해 요구된다.In addition, in the soliton system, the firing power for pulses using more powerful amplifiers can be increased to increase the spacing of the amplifiers. However, in this case, the equation (4) shows that if the reflected power is increased and the soliton pulse interval is kept constant, the ratio Dλ ² /

It also means that it should increase accordingly. Therefore, non-linear coefficients

Lower values of are required to provide increased distance between line amplifiers in soliton transmission systems.

The following patents and publications describe the design of optical transmission fibers using optical fibers having split core or double-cladding refractive index characteristics and large effective cross-sectional areas. For example, U.S. Patent (5,579,428) discloses single-mode fiber designed for use in WDM soliton telecommunication systems using optically focused or optically distributed amplifiers. Over the preselected wavelength range, the full dispersion for the disclosed optical fiber is within a preselected range of positive values high enough to balance the self-phase modulation for WDM soliton propagation. In addition, the dispersion slope is in a predetermined range at a sufficiently low value to prevent collisions between WDM solitons and to reduce time shifts and spectral shifts. The optical fiber proposed in the patent (5,579,428) is a split core having a maximum refractive index area in the core of the optical fiber.

U. S. Patent 4,715, 679 discloses an optical fiber having a split core of degraded refractive index for making low dispersion and low loss waveguides. The patent 4,715, 679 discloses a plurality of refractive index distributions including an ideal distribution having a maximum refractive index range in an annular region that is inside the outer core annular region but outside of the inner core of the optical fiber.

U. S. Patent 4,877, 304 discloses an optical fiber having the properties of a core having a maximum refractive index greater than the refractive index of the clad. U.S. Patent 4,889,404 discloses an asymmetric bidirectional optical communication system including optical fibers. Further, although the patents 4,877,304 and 4,889,404 describe an ideal refractive index distribution with perhaps an outer annular region of increased refractive index, an example corresponding to the distribution and the non-linear characteristics of the optical fiber having the distribution are given. There is no mention.

U.S. Patents 5,684,909, European Patents 789,255, and European Patents 724,171 disclose single mode optical fibers having a large effective cross-sectional area made of divided refractive index core properties. The patent and application disclose computer simulations for obtaining optical fibers with large effective cross-sectional areas for use in high bit rate optical systems over long distances. The patent (5,684,909) describes an optical fiber having two nonadjacent segments with positive refractive indices and two nonadjacent segments with negative refractive indices. For sake. The optical fiber disclosed in the European patents 789, 255 has at least two non-adjacent segments with an extremely large effective cross sectional area obtained by the refractive index with divided cores but with a negative refractive index difference. The European patents 724,171 disclose an optical fiber having a maximum refractive index present at the center of the optical fiber.

U. S. Patent 5,555, 340 discloses dispersion to compensate for an optical fiber having split cores to obtain dispersion compensation. The patent 5,555,340 discloses a refractive index distribution of a resin layer surrounding a cladding having a higher refractive index than the inner core of an optical fiber. However, the resin does not act as a low-loss light conducting layer in the optical fiber structure.

에 기여하는 것을 확인하였다. 굴절률을 증가하거나(예, GeO₂) 감소하기(예, 불소)위해 순수 실리카 유리에 첨가되는 도판트는 모두 순수 실리카의 비-선형 값 이상으로 유리의 비-선형을 증가시키는 경향이 있다. 출원인은 공지의 큰 실효 단면적의 광섬유가 실효 단면적의 전체적인 증가를 달성할 수 있지만, 광의 필드가 상대적으로 높은 강도를 가지는 광섬유 단면적 내의 도판트의 영향으로

의 최적 감소하는데는 실패한다는 것을 발견했다.Applicants noted that the distribution of refractive index modifying dopants in the optical fiber cross section has a large influence on the non-linear characteristics of the optical fiber. Applicants note that the non-linear coefficient n ₂ has a constant term due to pure silica and a non-linear coefficient with a radial variation term proportional to the concentration of the refractive index aqueous dopant.

It was confirmed to contribute to. Dopants added to pure silica glass to increase (eg GeO ₂ ) or decrease (eg fluorine) refractive index all tend to increase the non-linearity of the glass above the non-linear value of the pure silica. Applicants note that although known optical fibers of large effective cross-sectional area can achieve an overall increase in the effective cross-sectional area, due to the influence of dopants in the optical fiber cross-sectional area where the field of light has a relatively high intensity

Found that it failed to optimally decrease.

과 제한된 손실(limited loss)을 가지는 광섬유을 개발하는 작업을 제안하였다.In addition, Applicants noted that refractive index-modified-dopants have a tendency to increase fiber loss, especially because of increased scattering losses. In accordance with the above, Applicants have a low non-linear coefficient

We have proposed the work of developing optical fiber with limited loss.

Applicants have developed an optical fiber having a relatively low dopant concentration of higher light field intensity and a relatively high dopant concentration of lower light field intensity.

를 달성할 수 있음을 발견했다. 상기 광섬유에서 내부 코어 영역 외부의 광 필드 강도가 증가된다. 비교적 높은 광 필드 강도와 조합된 낮은-도판트 성분 영역의 존재는 광섬유 손실에 대한 제한된 영향과 함께 비-선형 계수의 실질적인 감소를 달성할 수 있다.Applicant selects a refractive index distribution having a first peak in the central cross-sectional area of the optical fiber, an outer ring having a second peak higher than the first peak, and a low-dopant-component region within the cross-sectional area between the two peaks. Low non-linear coefficients in optical fibers

Found that it can achieve. In the optical fiber the light field intensity outside the inner core region is increased. The presence of low-dopant component regions in combination with relatively high light field intensities can achieve a substantial reduction in non-linear coefficients with a limited effect on fiber loss.

와 높은 실효 단면적 영역을 가진 광 전송 섬유는 코어 영역과 코어 영역을 둘러싼 낮은 손실 클레딩을 구비한다. 코어 영역은 제 1 최대 굴절률차 Δn1, 분포α, 반경 r1을 가진 유리 내부 코어와; Δn1보다 작은 실질적으로 일정한 굴절률차 Δn2를 가진 내부 코어를 반경방향으로 둘러싸고 외부 반경이 r2인 제 1 유리층과; 제 1 층을 반경방향으로 둘러싸고 Δn1보다 큰 제 2 최대 굴절률차 Δn3을 가진 밑면의 폭이 W인 제 2 유리층을 구비한다. 여기서

은 미리 선정된 동작 파장 범위에 걸쳐서 약 W^-1km^-1보다 작다. 제 1 유리층의 굴절률차 Δn2는 상기 최대 굴절률차 Δn3 보다 절대치에 있어서 10% 작다. 더욱 바람직하게는 Δn2는 Δn3보다 절대치에 있어서, 5% 작다. 바람직하게 Δn2는 제 1 유리층 전체에 있어서 실질적으로 일정하다. In one aspect, the low non-linear coefficient according to the present invention

The optical transmission fiber having a high effective cross-sectional area has a core region and a low loss cladding surrounding the core region. The core region includes a glass inner core having a first maximum refractive index difference Δn 1, a distribution α, and a radius r 1; A first glass layer radially surrounding the inner core having a substantially constant refractive index difference Δn 2 less than Δn 1 and having an outer radius r2; And a second glass layer having a width W of the bottom surface that radially surrounds the first layer and has a second maximum refractive index difference Δn3 greater than Δn1. here

Is less than about W ⁻¹ km ⁻¹ over a pre-selected operating wavelength range. The refractive index difference Δn 2 of the first glass layer is 10% smaller in absolute value than the maximum refractive index difference Δn 3. More preferably, Δn 2 is 5% smaller in absolute value than Δn 3. Preferably Δn2 is substantially constant throughout the first glass layer.

Preferably, the peak of the second glass layer has a refractive index Δn3 of more than 5% of the peak refractive index Δn1 for the inner core.

를 가진 광 전송 섬유는, 코어 영역과 코어 영역을 둘러싼 낮은 손실 클레딩을 가진다. 코어 영역은 최대 굴절률 차가 Δn1과, 분포율 α, 그리고 반경 r1을 가지는 유리 내부 코어와 내부 코어를 반경방향으로 둘러싸고 Δn1보다 작은 굴절률차 Δn2를 가지고 외부 반경이 r2인 제 1 유리층; 그리고 Δn1보다 큰 제 2 최대 굴절률차Δn3과 폭이 w인 제 1 층을 둘러싼 제 2 유리층을 구비한다. 상기 제 1 유리층은 낮은-도판트-성분 영역을 구비한다. In a second aspect, the high effective area for use in the optical transmission system according to the invention and the non-linear coefficient less than about 2 W ⁻¹ km ⁻¹

The optical transmission fiber having a has a low loss cladding surrounding the core region and the core region. The core region includes: a first glass layer having a maximum refractive index difference Δn 1, a distribution ratio α, and a radius inner radius r1 and a glass inner core and an inner core in a radial direction, and having a refractive index difference Δn 2 smaller than Δn 1 and having an outer radius r 2; And a second maximum refractive index difference Δn3 larger than Δn1 and a second glass layer surrounding the first layer having a width w. The first glass layer has a low-dopant-component region.

In another aspect, the same light transmission system according to the invention comprises an optical transmitter for outputting an optical signal and an optical transmission line for transmitting the signal. The light transmission line includes an outer ring having a first index of refraction and a second index of refraction higher than the first peak in the central cross-sectional area of the optical fiber and a light transmission fiber having a low-dopant component region between the two peaks.

Preferably, the low-dopant-component region has about 15% or less of the peak refractive index difference of the optical fiber, that is, the refractive index difference of the outer ring.

In a preferred embodiment, an optical transmission system comprises a plurality of optical transmitters for outputting a plurality of optical signals each having a specific wavelength, the optical signals being combined and coupled to the optical transmission lines to form a wavelength division multiplexed optical communication signal. And an optical coupler for outputting a signal.

Preferably, the light transmitting fiber has a length longer than 50 km.

Advantageously, said optical transmission line comprises at least one amplifier.

In another aspect, the same method according to the invention for adjusting the non-linear effect in optical fiber transmission comprises the steps of: generating an optical signal; Coupling an optical signal to a silica optical fiber having a non-linear coefficient; A doping step for providing a first refractive index peak value in the central cross-sectional area of the optical fiber; Strengthening the field strength coupled with the optical signal in the optical fiber cross-sectional area outside of the central cross-sectional area by doping the annular glass ring of the optical fiber to provide a second refractive index peak value higher than the first peak value. The method comprises the step of selecting the dopant concentration of the fiber cross-sectional area between two peaks below a predetermined value to reduce the fiber non-linear coefficient.

It is to be understood that the foregoing general description and the following detailed description are exemplary of the invention only and are not intended to limit the invention as claimed. It is for explaining and showing the technique described below and the other advantages and objects of the present invention as practice of the present invention.

Various embodiments are cited according to the invention, embodiments of the invention are shown in the accompanying drawings and will become apparent from the description of the invention. In the drawings, the same reference numerals represent the same or similar components in different drawings.

와 비교적 높은 실효 면적을 포함하는 1520㎚에서 1620㎚의 파장 작동 범위에서 광 특징을 형성할 수 있다는 사실을 발견하였다. 이러한 특성에 따라 본 발명의 광섬유는, 특히 장거리(예를 들면, 50㎞ 이상)를 갖는 광 전송 라인 및 고 전력 신호(예를 들면, 광 증폭기를 갖는 광 송수신 라인)에서 효과적으로 사용될 수 있다.The optical fiber according to the invention has a refractive index distribution comprising two regions of peak refractive index difference in the radial dimension of the optical fiber, wherein the larger of the two peaks is located radially outward from the first peak. Applicants have found that optical fibers with refractive indices of the properties described above have relatively low non-linear coefficients.

It has been found that optical features can be formed in a wavelength operating range of 1520 nm to 1620 nm, which includes and relatively high effective area. According to these characteristics, the optical fiber of the present invention can be effectively used especially in optical transmission lines having a long distance (for example, 50 km or more) and high power signals (for example, optical transmission / reception lines with an optical amplifier).

Applicants also note that the optical fiber comprising the refractive index distribution is designed to minimize non-linear effects of four waveform mixing in a WDM system for both nonzero positive dispersion and nonzero negative dispersion. It was found that it can work effectively as dispersion fiber. In addition, the Applicant has determined that an optical fiber comprising the refractive index can effectively operate as a Dispersion Shifted Fiber to minimize non-linear effects in a light transmission system.

을 갖는 광 전송 섬유는 다른 굴절률을 가진 유리의 복수 광 전도층을 구비한다. 도 1의 광 전송 섬유(10)의 단면도에서 도시된 것처럼, 상기 광 전송 섬유의 축방향 중심은 가장 큰 굴절률차인 Δn1과 반경 r1을 갖는 내부 코어(12)이다. 당업자에게 쉽게 알려진 것처럼, 굴절률차는 유리의 주어진 층과 클래드 유리간의 굴절률차를 지칭한다. 즉, n1의 굴절률을 갖는 내부 코어(12)의 상기 굴절률차 Δn1은 n1-n클래드과 동일하다. 유리 코어(12)는 바람직하게, GeO₂와 같은 순수한 SiO₂의 굴절률을 증가시키는 물질로 도핑된 SiO₂로 구성된다. 굴절률을 증가시키는 다른 도판트는 예를 들면, Al₂O₃, P₂O₅, TiO₂, ZrO₂ 및 Nb₂O₃ 등이 있다. Referring to Figure 1, a low non-linear coefficient

The light transmitting fiber having the structure includes a plurality of light conducting layers of glass having different refractive indices. As shown in the cross-sectional view of the optical transmission fiber 10 of FIG. 1, the axial center of the optical transmission fiber is the inner core 12 having the largest refractive index difference Δn 1 and the radius r 1. As is readily known to those skilled in the art, the refractive index difference refers to the refractive index difference between a given layer of glass and the clad glass. That is, the refractive index difference Δn1 of the inner core 12 having a refractive index of n1 is the same as the n1-n cladding. Glass core 12 preferably consists of SiO ₂ doped with a material that increases the refractive index of pure SiO ₂ , such as GeO ₂ . Other dopants that increase the refractive index include, for example, Al ₂ O ₃ , P ₂ O ₅ , TiO ₂ , ZrO _2, and Nb ₂ O ₃ .

The first glass layer 14 surrounds the inner core 12 and is characterized by a widthwise refractive index of the layer that is smaller than the refractive index along the radius r1 of the inner core 12. Preferably, as will be explained in more detail below, the first glass layer 14 is made of pure SiO ₂ with a refractive index difference Δn ₂ that is substantially equal to zero.

The second glass layer 16 surrounds the first glass layer 14 along the length of the light transmitting fiber 10. At this time, the second glass layer 16 has a maximum refractive index Δn3 exceeding the maximum refractive index Δn1 of the glass in the inner core 12 in its width. Finally, the low loss clad layer 18 surrounds the second glass layer 16 in a conventional manner that aids light propagation along the axis of the light transmitting fiber 10.

Clad 18 may comprise pure SiO ₂ glass with a refractive index difference that is substantially zero. If the cladding 18 includes a refractive index-modifying-dopant, the cladding 18 should have a width index of refraction of the clad that is less than the maximum refractive index in the inner core 12 and the second glass layer 16.

2 shows the radial refractive index distribution of the light transmitting fiber 10 for the first embodiment of the present invention. As shown throughout, the light transmitting fiber has two refractive index peaks 20, 22 positioned respectively within the inner core 12 and the second glass layer 16. The first glass layer 14 radially disposed between the inner core 12 and the second glass layer 16 creates a refractive index dip for the two adjacent layers 12 and 16. .

 As a result, the combination of the inner core 12, the first glass layer 14 and the second glass layer 16 is generally characterized by the fact that the optical fiber has a split core comprising an outer layer having a maximum refractive index in the cross section of the core. Provide refractive index distribution.

As shown in FIG. 2, according to the first embodiment of the invention, the inner core 12 has a radius r1 which is about 3.6 μm to 4.2 μm and preferably 3.9 μm. Inner core 12 is between the center and the radial position of the optical fiber is GeO ₂ or 3.9 ㎛, peak in the axial center or in the vicinity of the optical transmission fiber (10) Dopants that increase the refractive index, such as creating a minimum refractive index for the inner core at the refractive index and the outer radius of the optical fiber.

The refractive index difference of the inner core 12 at the peak value is about 0.0082 to 0.0095, preferably about 0.0085. The dopant concentration that increases the refractive index is reduced to an outer diameter of 3.9 μm at the center of the inner core 12 in a manner that produces a distribution with a curved slope that resembles a parabolic shape in practice. The practically preferred parabolic shape corresponds to a distribution ratio α of between 1.7 and 2.0, preferably 1.9. In general, the distribution ratio of the inner core 12 may be expressed as the following equation as α.

 As is readily known to those skilled in the art, the distribution rate α indicates the roundness or curvature of the core, where α = 1 represents a triangular shape for the glass core and α = 2 represents a parabola. As the value of α is larger than 2 or close to 6, the refractive index distribution becomes almost close to the stepped refractive index distribution. In addition, while the correct stepped distribution is described as infinite α, α of about 4 to 6 is a stepped distribution for practical purposes. The distribution rate α causes a decrease in refractive index, such as an inverted cone shape, if the fiber is produced by OVD or MCVD methods.

The first glass layer 14 has a refractive index difference Δn 2, which is represented by 24 less than Δn 1. As shown in FIG. 2, the preferred refractive index difference Δn 2 of this first glass layer 14 has a constant value of about 0, which corresponds to a pure SiO ₂ glass layer. However, if the dopant component of the first glass layer 14 is low, the refractive index difference Δn 2 of the first glass layer 14 differs from zero due to the presence of dopants that change the refractive index. It is thought that the refractive index difference changes across the first glass layer 14. In any case, dopants that change the refractive index from the inner core 12 or from the second glass layer 16 can diffuse into the first glass layer 14 during optical fiber fabrication.

Applicants have a low-dopant component in the first glass layer 14 to obtain the above-described advantages (eg, low loss of fiber and low non-linearity) in combination with a relatively high field in the first glass layer 14. This absolute value leads to a refractive index difference Δn 2 in the first glass layer 14 corresponding to about 15% or preferably less than 15% of the optical fiber peak refractive index difference, for example, the refractive index difference of the second glass layer 16. It was concluded that it was a dopant component. Those skilled in the art will appreciate that the resulting optical fiber has non-linear and / or loss characteristics such as the length of the optical transmission line, the number and spacing of the amplifiers and / or the characteristics of the optical system, such as the power, number and wavelength spacing of the transmission signal. The value can be applied to match.

According to a preferred embodiment, the improved optical fiber properties can be achieved with the dopant concentration in the first glass layer 14 such that the absolute value causes a refractive index difference Δn 2 less than 10% of the refractive index difference Δn 3 of the second glass layer 16. have. The low dopant component in the first fiber layer has a very limited effect on non-linear modulus and loss in combination with the relatively high field of the optical fiber layer.

Further preferred optical fiber characteristics can be achieved with a refractive index difference Δn 2 whose absolute value is lower than 5% of the refractive index difference Δn 3 of the second glass layer 16.

The first glass layer 14 has an outer radius r2 that is between about 9.0 μm and 12.0 μm, or preferably 9.2 μm, as shown in FIG. 2. As a result, for the first embodiment of the present invention, the first glass layer 14 has a width from about 4.8 μm to about 8.4 μm.

Like the inner core 12, the second glass layer 16 has a refractive index difference that is increased or decreased by doping the width of the glass layer with Ge0 ₂ and / or other known dopants. The second glass layer 16 is at the highest point at the maximum refractive index difference Δn3 exceeding the maximum refractive index difference Δn1 of the glass core 12 and the refractive index difference Δn2 of the first glass layer 14, as shown in FIG. 2. It has a substantial parabolic distribution of its outer radius. Or a refractive index distribution different from the parabola, for example rounded or stepped, is considered to be the second glass layer 16.

Preferably, the refractive index Δn 3 of the second glass layer 16 exceeds the refractive peak rate Δn 1 for the inner core 12 at the refractive index peak by 5% or more. The refractive index Δn 3 of the second glass layer 16 is about 0.009 to 0.012, preferably about 0.0115, at the refractive index peak. The second glass layer 16 has a width w of about 0.6 μm to 1.0 μm, preferably about 0.9 μm.

The cladding 18 of the light transmitting fiber 10 has a refractive index distribution 26 having a refractive index difference that is substantially equal to zero. As mentioned, preferably the cladding 26 is pure SiO ₂ glass, but will include a dopant that does not raise the refractive index above the maximum refractive indices 20 and 22 of the inner core 12 and the second glass layer 16. Can be.

Applicants have found that the optical transmission fiber 10 having the refractive index distribution of FIG. 2 has several desirable optical characteristics for use in WDM transmission. Preferably, the optical transmission fiber 10 is used in a transmission system operating on a wavelength range of 1530 nm to 1565 nm and in which the optical fiber provides a total dispersion of 5 to 10 ps / nm / km over the operating wavelength range. More specifically, the optical transmission fiber 10 exhibits the following optical characteristics in the above wavelength range, and in parentheses the characteristics of the most preferred embodiment.

＜2W^-1km^-1(1.4W^-1km^-1@1550nm)
λ_cutoff＜1480nm(ITU.T G.650에 따른 광섬유 차단 파장(fiber cutoff wavelength))Dispersion = 5-10 ps / nm / km (5.65 ps / nm / km @ 1550nm)
Dispersion slope (dispersion slope) @ 1550nm≤0.06ps / nm 2 /km(0.056ps/nm 2 / km)
Macro Bending Attenuation Coefficient @ 1550nm <1dB / km
Effective area> 45 μm ²

<2W ^-1 km ^-1 (1.4W ^-1 km ^-1 @ 1550nm)
λ _cutoff <1480 nm (fiber cutoff wavelength according to ITU.T G.650)

The gain light feature satisfies the desired quality for optical transmission fibers for WDM systems of both soliton and non-soliton types.

는 비-선형 효과에 광 전송 섬유의 자화율(susceptibility)의 표시를 제공한다. 2 W^-1km^-1 보다 작은

을 가진 광 전송 섬유(10)는 그렇지 않으면 자기-위상 변조, 교차-위상 변조 및 그와 유사한 것으로부터 심각한 문제점을 일으킬 수 있는 고 전력 광 송수신 시스템에 있어서 호의적인 응답을 나타낸다. 마찬가지로, 광 전송 섬유(10)는 작동 범위 1530nm 내지 1565nm에 걸쳐서 횡단하는 비제로 분산 값을 포함하고, 상기 분산 값은 바람직하지 않은 4개의 파형 혼합을 막는 것을 돕는다. 또한, 작동 파장 범위에 걸쳐서 전체 분산의 비교적 작은 기울기는 광 전송 섬유(10)가 WDM 시스템에서의 반송 파장들 사이에 비교적 작은 차의 분산을 제공할 수 있도록 한다.As mentioned, the non-linear coefficient

Provides an indication of the susceptibility of the light transmission fiber to the non-linear effect. Less than 2 W ^-1 km ^-1

The optical transmission fiber 10 with a positive response exhibits a favorable response in a high power optical transmit / receive system which may otherwise cause serious problems from self-phase modulation, cross-phase modulation and the like. Likewise, the optical transmission fiber 10 includes non-zero dispersion values that traverse over the operating range 1530 nm to 1565 nm, which helps to prevent undesirable mixing of four waveforms. In addition, the relatively small slope of the overall dispersion over the operating wavelength range allows the optical transmission fiber 10 to provide a relatively small difference in dispersion between carrier wavelengths in the WDM system.

3 to 6 show in detail the relationship between the physical and optical characteristics of the light transmitting fiber 10. The figures show six parameters: radius r1 of inner core 12, maximum refractive index Δn1 of inner core 12, distribution shape α of inner core 12, outer radius r2 of first glass layer 14, Considering the width w of the second glass layer 16 and the maximum index of refraction Δn3 of the second glass layer 16, the results of the computer simulation of the optical transmission fiber 10 for various physical and optical relationships are shown. In the simulations represented by the respective graphs of FIGS. 3 to 6, the six parameters are in the range of six parameters in which these six parameters are substantially described above, namely r1 of 3.6 to 4.2 μm, Δn1 of 1.7 to 0.0095 μm, and 1.7. Α of from 2.0 to 9.0, r2 of 9.0 to 12.0 μm, w of 0.6 to 1.0 μm and Δn3 of 0.009 to 0.012 were changed at random. Each point represents a different set of six parameters. The simulation only considered a parameter set with Δn1 <Δn3. Thus, all the points correspond to fibers with an external refractive index peak higher than the internal peak.

는 낮아지게 됨을 발견하였다. As shown in the simulation results of FIGS. 3 to 6, in order to obtain an optical fiber having a low non-linear factor, the region of the refractive index distribution for the inner core 12 must be lowered. The outer ring with increased refractive index, in particular the second glass layer 16, is laid to help obtain a high effective cross sectional area and a low non-linear coefficient for the light transmitting fiber 10. In particular, Applicants note that the non-linear coefficient is because the laying of the second glass layer with increased refractive index lowers the dopant component at the center of the optical fiber by increasing the electric field distribution in the cross section of the optical fiber in the region having the low dopant component.

Found to be lowered.

Applicants also note that the laying of the second glass layer with increased refractive index has a low effect on the total optical fiber dispersion and that the optical fiber dispersion is substantially determined by the radial dimension r1 of the refractive index distribution of the inner core 12. I found out.

3 shows the relationship between the radius r1 and the dispersion of the light transmitting fiber 10. The value of r1 is preferably smaller than 3λ to achieve monomodal behavior at a given wavelength λ. For a given dispersion range, an appropriate range of radial dimensions r1 for the refractive index distribution can be determined.

The effective cross-sectional area of the light transmitting fiber 10 to prevent non-linear effects and to enable greater power should be kept relatively high, preferably in excess of 45 μm ² . Non-linear coefficients reduce the area of the refractive index distribution (ie the area area between the peak 20 and the coordinate axis of FIG. 2) for the inner core (see FIGS. 4-5) in two ways: Or by increasing the refractive index of the second outer peak (FIG. 6).

For the sake of clarity, the radial dimension r1 has remained constant in the simulation, so in this figure the variance is substantially determined. In order to reduce the area of the refractive index distribution for the inner core, it is effective to reduce the refractive index difference Δn1 for a given radial dimension r1. As the refractive index Δn1 is lowered, the effective cross sectional area increases because the confinement of the electric field in the inner core 12 becomes weaker, as shown in FIG.

를 생기게 한다. 그러므로, 보다 작은 비-선형 계수

를 갖는 상기 광 전송 섬유(10)는 증가된 전력을 취급할 수 있고 및/또는 비-선형 효과를 감소시킬 수 있다. Since the reduction of the refractive index distribution area for the inner core leads to an increased effective cross sectional area for the optical fiber, the reduction of the area is also smaller non-linear coefficient, as shown in FIG.

To produce. Therefore, smaller non-linear coefficients

The optical transmission fiber 10 with can handle increased power and / or reduce non-linear effects.

를 얻는 것을 도울 것이라는 것을 인식했다.Applicants further note that the addition of a lateral area with a higher refractive index located radially outward from the inner core results in a relatively large effective cross-sectional area and therefore a low non-linear coefficient.

Recognized it would help to get it.

The addition of the lateral peak refractive index zone helps to make the electric field distribution larger, but does not actually affect the dispersion. The radial position of the second glass layer 16, its width and its peak refractive index all affect the overall effective cross-sectional area of the optical fiber. For example, FIG. 6 shows the results of a computer simulation comparing the effective cross-sectional area and the peak refractive index difference for the second glass layer 16, where the other optical fiber parameters are kept constant for clarity. As demonstrated in FIG. 6, the increasing refractive index difference for the outer ring 16 produces an increasing effective cross sectional area for the light transmitting fiber 10.

7 shows the enlargement of the electric field in the cross-section of the light transmitting fiber 10 due to the addition of the outer ring 16. In FIG. 7, reference numerals 20 and 22 denote inner cores and outer rings, respectively, while reference numeral 23 denotes the electric field distribution over the optical fiber radius. The presence of the outer peak extends the electric field distribution in the optical fiber.

의 적, 즉, 동일한 실효 단면적을 갖는 다른 광섬유와 비교하여 보다 작은

를 나타내는 것을 확인했다. 예를 들면, 도 8a는 제1 실시예에 따른 광 전송 섬유(10)에 대한 실효 단면적과

사이의 시뮬레이트된 관계를 도시한다. 대조적으로, 도 8b는 종래 이중-형태의 분산-시프트형 광섬유에 대한

과 실효 단면적 사이의 시뮬레이트된 관계를 도시하고, 상기 광섬유는 보다 덜 바람직한(즉, 보다 높은) A_eff·

적을 나타낸다. Applicants also note that, as shown in the distribution of FIG. 2, an optical fiber having a maximum refractive index region in the outer ring of the core has a low A _eff.

Is less than that of other optical fibers with the same effective cross-sectional area

It confirmed that it represents. For example, FIG. 8A shows an effective cross-sectional area for the optical transmission fiber 10 according to the first embodiment.

The simulated relationship between them is shown. In contrast, FIG. 8B illustrates a conventional dual-type dispersion-shifted optical fiber.

And the simulated relationship between the effective cross-sectional area and the optical fiber is less desirable (ie higher) A _eff ·

Indicates an enemy.

In summary, the optical transmission fiber 10 provides an optical waveguide with a unique refractive index distribution for transmitting optical WDM signals with nonzero dispersion and relatively low non-linear coefficients. This feature allows the optical transmission fiber 10 to minimize signal degradation due to the mixing of the four waveforms and / or to use higher power.

FIG. 9 shows a second embodiment of the present invention for the light transmitting fiber 10 of FIG. 1. In the second embodiment, the inner core 12 has a radius r1 of about 2.3 μm to 3.6 μm, preferably about 2.77 μm. Between the center of the fiber and the 2.77 μm radial position, the inner core 12 produces a GeO that produces a peak index of refraction at or near the axis center of the optical transmission fiber 10 and a minimum with respect to the inner core in its outer radius. One or more refractive index increasing dopants, such as _two . At this peak value the refractive index Δn1 for the inner core 12 in the second embodiment is about 0.010 to about 0.012 and preferably about 0.0113. As in the first embodiment, the concentration of the refractive index-modified dopant in the core 12 is reduced from the center to an outer radius of about 2.77 μm to produce a distribution having a distribution ratio α of about 1.4 to about 3.0, preferably about 2.42. In the second embodiment, the first glass layer 14 has a substantially constant refractive index difference Δn 2, which is about zero due to the silica glass not doped with 24. The refractive index difference is. However, as previously described with reference to the first embodiment of FIG. 2, low dopant concentrations may be present in the first glass layer 14. The first glass layer 14 extends to an outer radius r2, such as between about 4.4 μm and 6.1 μm or more preferably 5.26 μm. As a result, the first glass layer 14 has an expanded width of about 0.8 μm to about 3.8 μm or preferably about 2.49 μm with respect to the second embodiment of the present invention.

Like the first embodiment, the second embodiment has a second glass layer 16, such as the inner core 12, having an increased refractive index difference by doping the width of the glass layer with CEO ₂ or another known refractive index increasing dopant. ) And / or other well known refractive index increasing dopants. The second glass layer 16 has a substantially parabolic distribution, reaching its highest point at the maximum refractive index difference Δn3 indicated by (22) of FIG. 9 over its radius. In addition, a refractive index distribution other than parabolic, for example, round or stepped, is also considered for the second glass layer 16.

Preferably, the refractive index Δn3 of the second glass layer 16 exceeds the peak refractive index Δn1 for the inner core 12 at a peak of this refractive index by 5% or more. The refractive index Δn 3 of the second glass layer 16 is about 0.012 to 0.014 or preferably about 0.0122 at the peak of this refractive index.

The second glass layer 16 has a width w equal to about 1.00 μm to about 1.26 μm, preferably about 1.24 μm.

Preferably, the optical transmission fiber 10 is used in a transmission system that operates over a wavelength range 1530 nm to 1565 nm where the fiber provides non-zero positive dispersion properties. Non-zero dispersed fibers are described in ITU-T Recommendation G.655.

The optical transmission fiber 10 constructed in accordance with the second embodiment of Figure 9 exhibits the following desirable optical properties (unless otherwise indicated, the values appear for values of 1550 nm):

Color dispersion at 1530 nm ≥ 0.5 ps / nm / km

0.07 ps / nm ² / km ≤ dispersion slope≤ 0.11ps / nm ² / km

45μm ² ≤A _eff ≤100μm ²

≤2W^-1km^-1 1W ^-1 km ^-1 ≤

≤2W ^-1 km ^-1

Microbending Attenuation Coefficient≤0.01 dB / km

(A loosely wound fiber with 100 turns at a bent radius of 30 mm)

Macro Bending Sensitivity≤10 (dB / km) / (g / mm)

λ _cutoff ≤ 1600 nm (fiber cut wavelength according to ITU.T G.650)

The second embodiment of the optical transmission fiber 10 having the above optical properties provides an acceptable condition for the transmission of both soliton and non-soliton WDM systems.

FIG. 10 shows the refractive index distribution of the third embodiment of the present invention for the light transmitting fiber 10, the cross section of which is shown in FIG. 1. As with the first and second embodiments, the third embodiment has a high refractive index difference with the first layer of glass having a smaller refractive index difference Δn 2 and a second layer of glass having a maximum refractive index difference Δn 3 at the cross-section of the light transmitting fiber. An inner core having Δn1 and a distribution form α.

The following shows the preferred physical parameters for the optical transmission fiber 10 according to the third embodiment of the present invention as shown in FIG.

Inner core radius r1 = 2.387μm

Inner core refractive index difference Δn1 = 0.0120

1st layer radius r2 = 5.355μm

First layer refractive index difference Δn2 = 0.0

2nd layer width w = 1.129μm

Second layer refractive index difference Δn3 = 0.0129.

Of course, the deviation from the value of the optimal structure does not affect the general inventive feature of these values. The optical transmission fiber 10 according to the third embodiment of the present invention advantageously obtains the following optimal optical properties (at wavelength 1550 nm).

Dispersion = 3.4ps / nm / km

Dispersion slope = 0.11 ps / nm ² / km

Mode Field Diameter = 9.95 μm

Effective cross section = 90 μm ²

= 1.00W^-1km^-1

= 1.00 W ^-1 km ^-1

The third embodiment of the optical transmission fiber 10 having the optical properties listed above provides an acceptable condition for transmission in both soliton and 1-soliton WDM systems.

FIG. 11 shows a fourth index of refraction distribution for light transmitting fiber 10 which produces non-zero positive dispersion of optical properties. The physical features of the inventive optical transmission fiber of FIG. 11 include a radius r1 of an inner core 12 of about 3.2 μm, a refractive index distribution α of an inner core 12 of about 2.9, an inner core of about 0.0088 at reference numeral 20. (12) the outer radius of the first glass layer 14 of about 7.2 μm having a maximum refractive index difference Δn 1, a refractive index difference Δn 2 of about 0 at 24, of the second glass layer 16 of about 0.8 μm. And a maximum refractive index Δn 3 of the second glass layer 16 of about 0.0119 in width and reference 22. As in the refractive index distribution of FIG. 2, the distribution of FIG. 11 for a non-zero positive dispersion fiber has a characteristic multi-peak high refractive index, with an outer peak present in the second glass layer 16, substantially parabolic, peak At maximum 22 the maximum refractive index 20 in the inner core 12 is exceeded. The optical transmission fiber 10 having the refractive index distribution of FIG. 11 provides a positive total fiber dispersion over a working wavelength band of 1530 nm to 1565 nm. Such performance has desirable applications in optical systems that have relatively high optical power and otherwise result in four waveform mixing results that are not beneficial.

FIG. 12 illustrates the relationship of simulated total dispersion band wavelengths for the optical transmission fiber 10 having the refractive index distribution of FIG. 11. As shown in the figure, the refractive index distribution of FIG. 11 produces dispersion over a wavelength band of about 1530 nm to about 1565 nm extending between about 0.76 ps / km / nm and 3.28 ps / km / nm. In particular, the fiber having the refractive index distribution shown in FIG. 11 provides the following optical properties at 1550 nm:

Dispersion = 2.18ps / nm / km

Dispersion slope = 0.072ps / nm ² / km

Macro bending attenuation factor = 0.01 dB / km

Mode Field Diameter = 9.0μm

Effective cross section = 62 μm ²

= 1.8W^-1km^-1

= 1.8 W ^-1 km ^-1

All of these properties fall within the range described by the ITU-T G.655 recommendation for non-zero dispersed fibers.

 FIG. 13 shows a fifth index of refraction distribution for light transmitting fiber 10 that produces optical properties of non-zero negative dispersion with relatively low non-linear coefficients. The physical properties of the inventive optical fiber of FIG. 13 range from about 2.4 μm to 3.2 μm, preferably about 2.6 μm of inner core 12 radius r1, about 1.8 to 3.0 preferably about 2.48 of inner core 12 refractive index distribution. α, about 5.3 μm with a refractive index difference Δn 1 for the inner core 12 of about 0.0106 to 0.0120, preferably about 0.0116, and about 0, preferably about 0, at reference numeral 20. From 6.3 μm, preferably about 5.9 μm, of the outer radius of the first glass layer 14, from about 1.00 μm to 1.08 μm, preferably about 1.08 μm, of the width of the second glass layer 16, and at 22. From about 0.0120 to 0.0132 preferably about 0.0129 of the second glass layer 16. As previously described, low dopant concentrations may be present in the first glass layer 14. As with the refractive index distributions of FIGS. 2, 9, 10 and 11, the refractive index distribution of FIG. 13 for a non-zero negative dispersed optical fiber has a number of peaks characteristic of high refractive index, with external peaks present in the second glass layer 16. In this case it actually has a parabolic slope and at its maximum 22 exceeds the maximum refractive index 20 in the inner core 12. In addition, refractive index distributions other than parabolas, for example, a refractive index distribution such as rounded or stepped, are considered for the second glass layer 16. Preferably, the refractive index Δn3 of the second glass layer 16 exceeds the peak refractive index Δn1 for the inner core 12 at the refractive index peak by 5% or more.

FIG. 10 with the refractive index of FIG. 13 results in negative full fiber dispersion over the operating wavelength band of 1530 nm to 1565 nm. Such performance has a desirable application in optical systems used in underwater transmission systems with relatively high optical power, which would result in four waveform mixing results which would otherwise be of no benefit. In particular, the fibers having a refractive index distribution shown in FIG. 13 represent the most preferred embodiment properties in parentheses and provide the following optical properties at 1550 nm.

Dispersion ≤ -0.5ps / nm / km (-2.46ps / nm / km)

0.07 ps / nm ² / km ≤ dispersion slope≤ 0.12ps / nm ² / km (0.11ps / nm ² / km)

Microbending Attenuation Coefficient≤0.01 dB / km (0.0004 dBm)

Mode field diameter = 9.1μm

45 μm ² ≤ effective cross section ≤ 75 μm ² (68 μm ² )

≤2W^-1km^-1(1.3W^-1km^-1)1.2W ^-1 km ^-1 ≤

≤2W ^-1 km ^-1 (1.3W ^-1 km ^-1 )

λ _cutoff ≤ 1600 nm (fiber cut wavelength according to ITU.T G.650)

A sixth refractive index distribution for the optical transmission fiber 10 that produces a dispersion shift optical feature with a relatively low non-linear coefficient is described. Distributed shift fiber is described in ITU-T Recommendation G.653. The physical feature of the optical fiber according to the sixth embodiment is an inner core 12 radius r1 of about 3.2 μm, a refractive index distribution α for the inner core 12 of about 2.8, an inner core of about 0.0092 in reference numeral 20. The maximum refractive index difference Δn1 for (12), the width of the second glass layer with an outer radius of about 0.8 μm of the first glass layer 14 of about 7.8 μm with a refractive index Δn2 of about 0, and a second glass layer of about 0.0118. The maximum refractive index Δn 3 of (16). As in the refractive index distributions of FIGS. 2, 9, 10, 11 and 13, the distribution for the dispersion shift type optical fiber according to the sixth embodiment has a characteristic multiple peak of high refractive index, where the outer peak is the second glass layer. It exists at (16), has a substantially parabolic shape, and at the maximum peak (22), exceeds the maximum refractive index (20) in the inner core (12). Alternatively, a refractive index distribution different from the parabola, for example rounded or stepped, is also contemplated for the second glass layer 16. Preferably, the refractive index Δn 3 of the second glass layer 16 exceeds the peak refractive index Δn 1 with respect to the inner core 12 at a refractive index peak of 5% or more.

 The optical transmission fiber 10 having the refractive index distribution of FIG. 13 provides a low absolute value total fiber dispersion over an operating wavelength band of 1530 nm to 1565 nm.

In particular, the fibers give rise to the following optical properties, indicated at 1550 nm unless otherwise indicated.

  Dispersion = 0.42 ps / nm / km

Dispersion slope = 0.066 ps / nm ² / km

Dispersion @ 1525nm = -1.07 ps / nm / km

Dispersion @ 1575nm = +2.22 ps / nm / km

Macro bending attenuation factor = 0.6 dB / km

Mode Field Diameter = 8.8 μm

Effective cross section = 58 μm ²

= 1.56 W^-1km^-1

= 1.56 W ^-1 km ^-1

λ _cutoff = 1359 nm (fiber cut wavelength according to ITU.T G.650)

Various modifications and changes may be made to the systems and methods of the present invention by those skilled in the art without departing from the scope and spirit of the invention. For example, the refractive index distribution shown in the figures is intended to be an illustration of the preferred embodiment. The exact shape, radial distance and refractive index differences can be easily changed by those skilled in the art to obtain the same optical fiber as disclosed herein without departing from the scope or spirit of the invention. Although optical fiber operation in the wavelength range between 1530 nm and 1565 nm has been disclosed for certain embodiments, signals of other wavelength ranges may be transmitted and received in the optical fiber according to the present invention if specific wavelength requirements arise in current or future optical communication systems. have. In particular, those skilled in the art can contemplate the use of optical fibers, or simple modifications thereof, described to operate in an extended wavelength range between about 1520 nm and about 1620 nm, while maintaining low attenuation properties.

It is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Included in the above

Claims (26)

Low non-linear coefficients for use in optical transmission systems

And a light transmitting fiber having a high effective cross-sectional area, A glass inner core having a first maximum refractive index difference Δn 1, a distribution ratio α, and a radius r 1; A first glass layer having a refractive index difference Δn 2 and an outer radius r 2 that is smaller than Δ n 1 and radially surrounding the inner core; And A core region having a second maximum refractive index difference Δn3 greater than Δn1, a width w, and comprising a second glass layer radially surrounding the first layer; And, A low loss cladding surrounding the core region, the non-linear coefficients

Is less than 2W ⁻¹ K ⁻¹ and the refractive index difference Δn 2 is less than 10% of the second refractive index difference Δn 3 in absolute value. The optical transmission fiber of claim 1, wherein r1 is about 3.6 μm to 4.2 μm, r2 is about 9.0 μm to 12.0 μm, and w is about 0.6 μm to 1.0 μm. The optical transmission fiber according to claim 2, wherein α is about 1.7 to 2.0. 4. The light transmission fiber according to claim 2 or 3, wherein Δn3 is about 0.009 to 0.012. 5. The optical transmission fiber according to claim 4, wherein Δn1 is about 0.0082 to 0.0095. The optical transmission fiber of claim 1, wherein the total dispersion of the optical transmission fiber in the wavelength range of 1530 nm to 1565 nm is about 5 ps / nm / km to 10 ps / nm / km. The optical transmission fiber of claim 1, wherein r1 is about 2.3 μm to 3.6 μm, r2 is about 4.4 μm to 6.1 μm and w is about 1.00 μm to 1.26 μm. 8. A light transmitting fiber according to claim 7, wherein said a is from about 1.4 to 3.0. 9. The optical transmission fiber according to claim 7 or 8, wherein Δn3 is 0.0120 to 0,0140. 10. The optical transmission fiber according to claim 9, wherein the Δn1 is about 0.0100 to 0.0120. 8. The optical transmission fiber according to claim 7, wherein the total dispersion of the optical transmission fiber in the wavelength range of 1530 nm to 1565 nm is greater than 0.5 ps / nm / km. The optical transmission fiber of claim 1, wherein r1 is about 2.4 μm to 3.2 μm, r2 is about 5.3 to 6.3, and w is 1.00 μm to 1.08 μm. 13. The optical transmission fiber according to claim 12, wherein α is about 1.8 to 3.0. 14. The optical transmission fiber according to claim 12 or 13, wherein Δn3 is 0.0120 to 0.0132. 15. The optical transmission fiber according to claim 14, wherein Δn1 is about 0.0106 to 0.0120, and Δn2 is about 0.0. 13. The optical transmission fiber of claim 12, wherein the total dispersion for the optical transmission fiber in the wavelength range of 1530 nm to 1565 nm is less than about -0.5 ps / nm / km. The optical transmission fiber of claim 1, wherein Δn 2 is less than 5% of Δn 3 in absolute value. 18. The optical transmission fiber according to claim 17, wherein Δn2 is about 0.0. The optical transmission fiber according to claim 1, wherein the maximum refractive index difference of the second glass layer exceeds the maximum core refractive index difference Δn1 by 5% or more. High effective cross-sectional area and non-linear coefficient less than 2 W ^-1 km ^-1 for use in optical transmission systems

In the optical transmission fiber having a A glass inner core having a first maximum refractive index difference Δn 1, a distribution α, and a radius r 1; A first glass layer radially surrounding the glass inner core and having a refractive index difference Δn 2 and an outer radius r 2 less than Δn 1; And A core region radially surrounding the first glass layer and including a second glass layer having a second maximum refractive index difference Δn 3 and a width w greater than Δn 1; And, And a low loss cladding surrounding said core region, said first glass layer comprising a low dopant component region. An optical transmission system comprising an optical transmitter for outputting an optical signal and an optical transmission line for transmitting the optical signal, The optical transmission line includes an optical transmission fiber having a first refractive index peak value in the cross-sectional area at the center of the optical transmission fiber, an outer ring having a second refractive index peak value higher than the first peak value, and a low dopant component region between the two peaks. Optical transmission system comprising a. 22. The optical transmission system according to claim 21, wherein the low dopant component region has an absolute refractive index difference less than or equal to 15% of the optical transmission fiber peak refractive index difference. 22. The apparatus of claim 21, further comprising: a plurality of optical transmitters for outputting a plurality of optical signals, each signal having a particular wavelength; And And an optical coupler for combining the optical signals to form a wavelength division multiplex optical communication signal and for outputting the combined signals onto the optical transmission line. 22. The optical transmission system according to claim 21, wherein the optical transmission fiber has a length longer than 50 km. 22. The optical transmission system of claim 21 wherein the optical transmission line comprises an optical amplifier. A method for controlling a non-linear effect in optical fiber transmission, Generating an optical signal; Coupling an optical signal in a silica light transmission fiber with a non-linear coefficient; A doping step for providing a first index of refraction peak in the central cross-sectional area of the optical transmission fiber; Reinforcing an electric field strength for coupling the annular glass ring of the fiber to an optical signal in a fiber cross-sectional area that is outside of the central cross-sectional area by doping to provide a second refractive index peak value higher than a first peak value. In a way, Non-linear effect of optical fiber transmission, further comprising selecting a dopant concentration of the optical transmission fiber cross-sectional area between the two peak values lower than a predetermined value to reduce the fiber non-linear coefficient. Control method.

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