JP2005331818A - High nonlinearity optical fiber, method for manufacturing the same, and application of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high nonlinearity optical fiber having ample nonlinearity and proper dispersion flatness characteristic, a method for manufacturing the same, and a device which uses the same. <P>SOLUTION: The highly nonlinear optical fiber has a core region 10 with n1a refractive index, a first cladding region 11 with n2a refractive index located on the outside of the core region 10, and a second cladding region 12 with n3a refractive index located on the outside of the first cladding region 11, wherein the refractive indexes of the respective regions satisfy an inequality n1a>n3a>n2a, a ratio r(ba)/r(aa) of the radius r(aa), corresponding to a distance from the center of the core region to a position with a refractive index equal to the refractive index n3a in the core region to the radius r(ba) corresponding to the distance from the center of the core region to a position with a refractive index equal to the value (n1a+n3a)/2 in the core region is 0.8 or larger, and has 20μm<SP>2</SP>or less effective cross section A<SB>eff</SB>with respect to light with 1,550 nm wavelength, wavelength dispersion in (-2)-(+2) ps/nm/km range and 6/W/km or larger nonlinear coefficient. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a highly nonlinear optical fiber having a good dispersion flat characteristic and a manufacturing method thereof, a supercontinuum light generating device, an optical amplifier, a wavelength converter, and an optical pulse compression device using the highly nonlinear optical fiber.

In general, it is known that when high-intensity (high light density) light propagates through an optical fiber, nonlinear optical phenomena such as four-wave mixing, self-phase modulation, cross-phase modulation, and stimulated Brillouin scattering occur. When these phenomena occur in an optical fiber, wavelength conversion, phase modulation, scattering, etc. may occur, resulting in an increase in noise components and insufficient transmission of input light. For this reason, conventionally, attempts have been made to form an optical fiber for transmission while eliminating these nonlinear optical phenomena as much as possible.
On the other hand, in recent years, by actively utilizing the nonlinear optical phenomenon as described above, wavelength conversion for converting the wavelength of the signal light to the long wavelength side or the short wavelength side, optical amplification of the optical signal, waveform distortion of the signal light, etc. Attempts have been made to perform optical signal processing such as waveform shaping to adjust the optical fiber, and an optical fiber capable of performing optical signal processing using such a nonlinear optical phenomenon has also been proposed (for example, Patent Documents). 1 and 2).

The nonlinearity γ of the optical fiber is the nonlinear coefficient γ
γ = (2π / λ) × (n ₂ / A _eff )
It is represented by Here, λ is the wavelength of light, n ₂ is the nonlinear refractive index in the optical fiber, and A _eff is the effective cross-sectional area of the optical fiber. From this equation, in order to increase the nonlinear coefficient γ, the concentration of GeO ₂ added in the core of the optical fiber is increased to increase the nonlinear refractive index n ₂ and the relative refractive index between the core and the cladding. The effective area A _eff may be reduced by increasing the difference.
Among the highly nonlinear fibers, in particular, a highly nonlinear dispersion-shifted fiber (HNL-DSF) having a chromatic dispersion value of approximately zero near 1550 nm, which is the signal wavelength of light, is a highly efficient four-fiber. This is very important for the use of optical wave mixing (FWM) and the application of optical signal processing to short pulse light. Recently, in order to lower the dispersion value in the vicinity of the signal wavelength, a highly nonlinear fiber with a reduced dispersion slope has also been developed, and a highly nonlinear dispersion flat fiber (High Nonlinear Displacement-Flattened Fiber: HNL-) in which the dispersion slope is almost zero. DFF) has been published, and a wavelength conversion characteristic having a wide excitation light wavelength range is obtained by the dispersion flat characteristic of this optical fiber (for example, see Non-Patent Document 1).

A phenomenon in which when an intense short optical pulse is incident on an optical fiber, the output pulse exhibits an ultra-wideband spectrum is known as supercontinuum (SC) light, and its chromatic dispersion characteristic is flat and along the propagation direction. It is known that a super-continuum spectrum with higher efficiency and higher quality can be obtained by using an optical fiber (dispersion flat / reducing fiber) whose dispersion decreases (see, for example, Non-Patent Documents 1 to 4).
International Publication No. WO99 / 10770 JP 2002-207136 A Okuno et al., “Highly Nonlinear Dispersion Flat Fiber and its Applications”, IEICE Technical Report, OCS 2003-63, OFT 2003-45, August 2003 Mori et al., “Generation mechanism of supercontinuum in optical fiber”, IEICE Technical Report, OCS97-48, ED97-138, OPE97-93, LQE97-93, November 1997 Sone et al., “Supercontinuum Generation by Dispersion Flat / Decrease Fiber Considering Optical Wavelength Dependent Loss and Higher Order Dispersion and Nonlinear Effects”, IEICE Technical Report, OCS 98-72, ED 98-163, OPE 98-104, LQE 98-103, November 1998 Imai, "Generation of supercontinuum light using a dispersion characteristic changing fiber (DFDF: dispersion flat / decreasing fiber, tapered fiber)", IEICE Technical Report, OCS 2003-57, OFT 2003-39, August 2003 Sakai et al., “Delay Equalizer for Collective 3R Regenerative Relaying of WDM Signals”, IEICE Technical Report, OCS 2003-76, October 2003

Among the wavelength changes using four-wave mixing, highly nonlinear fibers used for wavelength conversion that makes the pumping light wavelength variable, and highly nonlinear fibers used for generating supercontinuum light have a wide dispersion range. Desirably flat. A dispersion flat fiber is known as such a fiber. However, a conventional dispersion flat fiber has a dispersion value and a dispersion slope at a signal light wavelength of 1550 nm which are almost zero, but has a shorter wavelength and a longer wavelength than 1550 nm. No mention is made of the dispersion value and dispersion slope for light. Therefore, even if the dispersion value and the dispersion slope at the signal light wavelength of 1550 nm are almost zero, the dispersion value may be far away from zero in the wavelength band other than 1550 nm, and the dispersion flat characteristic may be deteriorated. In order to improve the dispersion flat characteristic, not only the dispersion value and dispersion slope at the signal light wavelength of 1550 nm are brought close to zero, but also the dispersion value and dispersion slope for light having a shorter wavelength and longer wavelength than 1550 nm are made zero. It needs to be close, but the method is not known.
In addition, an all-optical 3R regenerative relay system that collects and regenerates WDM signals has been proposed as waveform shaping optical signal processing for adjusting the wavelength distortion of signal light. This is done using four-wave mixing in the optical fiber. As these problems, since WDM channels having different wavelengths are subjected to different propagation delays due to chromatic dispersion in the optical fiber, the arrival timing of WDM signals generally differs from channel to channel, making it difficult to perform batch recovery processing of WDM signals. It is to become. If the dispersion slope at the signal light wavelength of 1550 nm is large, even if the dispersion value is zero at 1550 nm, the dispersion value becomes large at the wavelengths before and after that, causing the above-described problems. In the all-optical 3R regenerative repeater system that regenerates WDM signals at once, the dispersion flat characteristic becomes important.

  The present invention has been made in view of the above circumstances, and has been made to solve the problems relating to dispersion flat characteristics, and a highly nonlinear optical fiber having sufficient nonlinearity and very good dispersion flat characteristics, and a method for manufacturing the same, An object of the present invention is to provide a supercontinuum light generating device, an optical amplifier, a wavelength converter, and an optical pulse compression device using the same.

In order to achieve the above object, a highly nonlinear optical fiber according to a first aspect of the present invention includes a core region having a refractive index nla, a first cladding region provided on the outer periphery of the core region and having a refractive index n2a, and the first And at least a second cladding region having a refractive index n3a provided on the outer periphery of the first cladding region,
The refractive index of each of these regions is n1a>n3a> n2a,
The radius from the center of the core region to the position having the same refractive index as the refractive index n3a in the core region is r (aa), and the refractive index is the same value as (n1a + n3a) / 2 in the core region from the center of the core region. An optical fiber having a core region where r (ba) / r (aa) is 0.8 or more, where r (ba) is a radius to a position having
As characteristics for light with a wavelength of 1550 nm,
An effective area A _eff of 20 μm ² or less,
A chromatic dispersion value of −2 ps / nm / km to +2 ps / nm / km,
Having a nonlinear coefficient of 6 / W / km or more,
The wavelength dispersion characteristic is characterized in that an absolute value of a difference between a wavelength dispersion value for light having a wavelength of 1550 nm and a wavelength dispersion value for light having a wavelength 100 nm away from 1550 nm is 2 ps / nm / km or less.

In addition to the configuration of the first invention, the highly nonlinear optical fiber of the second invention has a relative refractive index difference Δ1a of the core region with respect to the second cladding region of 1.0% or more, and the second cladding region. The relative refractive index difference Δ2a of the first cladding region with respect to is in the range of −0.4% or less, and the ratio r (ca) / r (aa) of the first cladding radius to the core radius is in the range of 1.8 to 2.6. It is characterized by being.
In the present specification, the relative refractive index difference Δ2a is defined by the following equation (1).
Δ2a = {(n2a−n3a) / n3a} × 100 (1)

  In addition to the configuration of the first invention, the highly nonlinear optical fiber of the third invention has a relative refractive index difference Δ1a of the core region with respect to the second cladding region of 1.4% or more, and the second cladding region The relative refractive index difference Δ2a of the first cladding region with respect to is in the range of −0.6% or less, and the ratio of the first cladding radius to the core radius r (ca) / r (aa) is in the range of 1.8 to 2.6. It is characterized by being.

  In addition to the structure of the first invention, the highly nonlinear optical fiber of the fourth invention has a relative refractive index difference Δ1a of the core region with respect to the second cladding region of 2.9% or more, and the second cladding region The relative refractive index difference Δ2a of the first cladding region with respect to the range of −1.0% or less, and the ratio of the first cladding radius to the core radius r (ca) / r (aa) is in the range of 1.8 to 2.6. It is characterized by being.

A highly nonlinear optical fiber according to a fifth aspect of the present invention is provided in a core region having a refractive index n1b, a first cladding region having a refractive index n2b, provided in an outer periphery of the core region, and provided in an outer periphery of the first cladding region. A second cladding region having a refractive index n3b; a third cladding region having a refractive index n4b; and a third cladding region having a refractive index n4b; and a third cladding region having a refractive index n5b. A fourth cladding region having at least
The refractive index of each of these regions is n1b ≧ n3b> n5b ≧ n4b> n2b,
A position having the same refractive index as the refractive index n4b from the center of the core region is defined as r (ab), and a position having a refractive index equal to (n1b + n4b) / 2 from the center of the core region to the core region. R (bb) is an optical fiber having a core region where r (bb) / r (ab) is 0.8 or more,
As characteristics for light with a wavelength of 1550 nm,
An effective area A _eff of 20 μm ² or less,
A chromatic dispersion value of −2 ps / nm / km to +2 ps / nm / km,
Having a nonlinear coefficient of 6 / W / km or more,
The wavelength dispersion characteristic is characterized in that the absolute value of the difference between the wavelength dispersion value for light having a wavelength of 1550 nm and the wavelength dispersion value for light having a wavelength 100 nm away from 1550 nm is 2 ps / nm / km or less.

In addition to the configuration of the fifth invention, the highly nonlinear optical fiber of the sixth invention has a relative refractive index difference Δ1b of the core region with respect to the third cladding region of 1.2% or more, and the third cladding region The relative refractive index difference Δ2b of the first cladding region relative to the third cladding region is −0.35% or less, the relative refractive index difference Δ3b of the second cladding region to the third cladding region is 0.2% or more, and the third cladding region The relative refractive index difference Δ4b of the fourth cladding region with respect to the region is 0.05% or more, and the ratio r (cb) / r (ab) of the first cladding radius to the core radius is in the range of 1.8 to 2.6. The ratio r (db) / r (ab) of the second cladding radius to the core radius is in the range of 2.6 to 3.4, and the ratio of the third cladding radius to the core radius r (eb) / r ( ab) is 4.0 or more.
In the present specification, the relative refractive index difference Δ2b is defined by the following equation (2).
Δ2b = {(n2b−n4b) / n4b} × 100 (2)

  In addition to the configuration of the fifth invention, the highly nonlinear optical fiber of the seventh invention has a relative refractive index difference Δ1b of the core region with respect to the third cladding region of 1.5% or more, and the third cladding region The relative refractive index difference Δ2b of the first cladding region relative to the third cladding region is −0.5% or less, the relative refractive index difference Δ3b of the second cladding region to the third cladding region is 0.3% or more, and the third cladding region The relative refractive index difference Δ4b of the fourth cladding region with respect to the region is 0.05% or more, and the ratio r (cb) / r (ab) of the first cladding radius to the core radius is in the range of 1.8 to 2.6. The ratio r (db) / r (ab) of the second cladding radius to the core radius is in the range of 2.6 to 3.4, and the ratio of the third cladding radius to the core radius r (eb) / r ( ab) is 4.0 or more.

  In addition to the configuration of the fifth invention, the highly nonlinear optical fiber of the eighth invention has a relative refractive index difference Δ1b of the core region with respect to the third cladding region of 3.0% or more, and the third cladding region The relative refractive index difference Δ2b of the first cladding region relative to the first cladding region is −0.8% or less, the relative refractive index difference Δ3b of the second cladding region to the third cladding region is 0.7% or more, and the third cladding region The relative refractive index difference Δ4b of the fourth cladding region with respect to the region is 0.05% or more, and the ratio r (cb) / r (ab) of the first cladding radius to the core radius is in the range of 1.8 to 2.6. The ratio r (db) / r (ab) of the second cladding radius to the core radius is in the range of 2.6 to 3.4, and the ratio of the third cladding radius to the core radius r (eb) / r ( ab) is 4.0 or more.

The highly nonlinear optical fiber of the ninth invention further has a chromatic dispersion slope of −0.01 ps / nm ² / km or more and +0.01 ps / nm ² / km or less as a characteristic with respect to light having a wavelength of 1550 nm, and chromatic dispersion It has a dispersion characteristic such that there is at least one wavelength of light having a slope of zero within a wavelength range of 1450 nm to 1650 nm.

  A highly nonlinear optical fiber according to a tenth invention is characterized by being provided with a stress applying portion structure and having a polarization maintaining ability.

The highly nonlinear optical fiber of the eleventh invention is characterized in that fluorine is added together with GeO _{2 in} the core region. Addition of GeO ₂ into quartz glass increases the refractive index, and addition of fluorine has an effect of decreasing the refractive index.

The highly nonlinear optical fiber of the twelfth invention is characterized in that fluorine is added together with GeO _{2 in the} core region, and the concentration of fluorine is 1% by mass or more.

  In the highly nonlinear optical fiber according to the thirteenth aspect, the chromatic dispersion value in light having a wavelength of 1550 nm changes substantially linearly along the longitudinal direction of the fiber, and the change is zero from the positive value of the chromatic dispersion value. It is characterized by a change to a negative value via.

  A method for manufacturing a highly nonlinear optical fiber according to a fourteenth aspect of the present invention is a method for manufacturing the highly nonlinear optical fiber according to any one of the first to thirteenth aspects, wherein a glass rod for a core serving as a core region is provided. After synthesizing by VAD method or OVD method and removing a part of the outer periphery of the synthesized core glass rod, a glass layer to be the first cladding region is synthesized on the outer periphery of the core glass rod, and further on the outer periphery The core glass rod comprises the steps of producing an optical fiber preform by sequentially synthesizing the glass layers to be provided for each cladding region and then drawing the optical fiber preform to produce a highly nonlinear optical fiber. In the step of removing a part of the outer periphery of the core, the refractive index of the central portion of the synthesized core glass rod is n1c, and the refractive index of the outermost peripheral portion of the core glass rod before the outer periphery is removed is n2. Assuming that r (bc) is a position having the same refractive index as (n1c + n2c) / 2 in the core glass rod, {r (bc) / core glass rod radius} is 0.8 or more. Thus, a part of the outer periphery of the core glass rod is removed.

  According to a fifteenth aspect of the present invention, there is provided a method of manufacturing a highly nonlinear optical fiber, wherein in the step of heating and drawing the optical fiber preform, the optical fiber is drawn so that the outer diameter of the optical fiber is sequentially reduced or expanded along the longitudinal direction. The chromatic dispersion value in the light with a wavelength of 1550 nm changes almost linearly along the longitudinal direction of the fiber, and the change is that the chromatic dispersion value changes from a positive value to a negative value via zero. It is characterized by obtaining a highly nonlinear optical fiber.

  According to a sixteenth aspect of the present invention, there is provided a supercontinuum light generating device comprising: the highly nonlinear optical fiber according to any one of the first to thirteenth aspects; and a pumping light source that supplies pumping light having a predetermined wavelength λp to the highly nonlinear optical fiber. The supercontinuum light is generated by using a nonlinear optical phenomenon that is generated by inputting a predetermined wavelength λp into the highly nonlinear optical fiber.

  An optical amplifier according to a seventeenth aspect of the present invention is an optical amplifier using the highly nonlinear optical fiber according to any one of the first to thirteenth aspects, and is manifested by inputting light of a predetermined wavelength into the highly nonlinear optical fiber. It is characterized by using a nonlinear optical phenomenon.

  A wavelength converter according to an eighteenth aspect of the present invention is a wavelength converter using the highly nonlinear optical fiber according to any one of the first to thirteenth aspects, wherein light having a predetermined wavelength is input to the highly nonlinear optical fiber. It utilizes the nonlinear optical phenomenon expressed by the above.

  An optical pulse compression apparatus according to a nineteenth aspect of the present invention is an optical pulse compression apparatus using the highly nonlinear optical fiber according to any one of the first to thirteenth aspects, wherein light of a predetermined wavelength is input to the highly nonlinear optical fiber. It is characterized by utilizing a nonlinear optical phenomenon that is manifested by doing so.

In the highly nonlinear optical fiber according to the first aspect of the invention, the dispersion value and dispersion slope at the signal light wavelength of 1550 nm are close to zero, and the dispersion value and dispersion slope for light having wavelengths shorter and longer than 1550 nm are also zero. It is possible to have a very good dispersion flat characteristic and sufficient nonlinearity.
The highly nonlinear optical fiber of the second invention can provide a highly nonlinear optical fiber in which the dispersion value and dispersion slope at the optical signal wavelength of 1550 nm are close to zero.
The highly nonlinear optical fibers of the third and fourth inventions have a smaller A _eff and a larger nonlinear coefficient γ, so that they have higher nonlinearity and have a dispersion value at a signal light wavelength of 1550 nm. A highly nonlinear optical fiber having a dispersion slope close to zero can be obtained.
In the highly nonlinear optical fiber according to the fifth aspect of the invention, the dispersion value and dispersion slope at the signal light wavelength of 1550 nm are close to zero, and the dispersion value and dispersion slope for light having wavelengths shorter and longer than 1550 nm are also zero. It is possible to have a very good dispersion flat characteristic and sufficient nonlinearity.
The highly nonlinear optical fiber according to the sixth aspect of the invention provides a highly nonlinear optical fiber having a dispersion value and dispersion slope at a signal light wavelength of 1550 nm that are close to zero.
The highly nonlinear optical fibers according to the seventh and eighth inventions have a smaller A _eff and a larger nonlinear coefficient γ, so that they have higher nonlinearity and have a dispersion value at a signal light wavelength of 1550 nm. An optical fiber having a dispersion slope close to zero can be obtained.
The highly nonlinear optical fiber of the ninth invention can have a very good dispersion flat characteristic in a wide wavelength range centered on a signal light wavelength of 1550 nm.
In the highly nonlinear optical fiber according to the tenth aspect of the invention, the optical fiber can have a polarization maintaining ability, and the expression of the nonlinear optical phenomenon becomes more efficient.
Eleventh highly nonlinear optical fiber invention, as substance added to the quartz glass of the core region is equal to the refractive index obtained when only GeO _2, fluorine with GeO ₂ in the quartz glass of the core region By adding, it becomes possible to add more GeO ₂ to the core region, increase the nonlinear refractive index n2, and have a larger nonlinearity.
In the highly nonlinear optical fiber according to the twelfth aspect of the present invention, when the fluorine concentration is 1% by mass or more, more GeO ₂ can be added to the core region, and the nonlinear refractive index n2 can be increased. It is possible to have a greater nonlinearity.
A highly nonlinear optical fiber according to a thirteenth aspect of the present invention is a highly nonlinear optical fiber capable of obtaining a high-efficiency and high-quality supercontinuum spectrum and having a flat chromatic dispersion characteristic and a reduced dispersion along the propagation direction. Dispersion flat / reducing fiber).

The manufacturing method of the fourteenth invention can easily and efficiently manufacture the highly nonlinear optical fiber of the first to thirteenth inventions. In addition, the dispersion value and dispersion slope at the signal light wavelength of 1550 nm are close to zero, and furthermore, the dispersion value and dispersion slope for light having a shorter wavelength and longer wavelength than 1550 nm can be brought close to zero, which is very good. It is possible to obtain a highly nonlinear optical fiber having excellent dispersion flat characteristics and sufficient nonlinearity.
The manufacturing method of the fifteenth aspect of the invention can obtain a highly efficient and high quality supercontinuum spectrum, a highly nonlinear optical fiber having a flat chromatic dispersion characteristic and a decrease in dispersion along the propagation direction (dispersion flat / Reduced fiber).

The supercontinuum light generating device according to the sixteenth aspect of the present invention is a phenomenon in which the spectral intensity spreads over a wide band and whitens by utilizing a nonlinear optical phenomenon expressed by inputting a predetermined wavelength λp into the highly nonlinear optical fiber. The supercontinuum light known as can be generated with high efficiency.
The optical amplifier according to the seventeenth aspect of the invention can perform optical amplification with high efficiency by utilizing a nonlinear optical phenomenon that is manifested by inputting light of a predetermined wavelength into a highly nonlinear optical fiber.
The wavelength converter of the eighteenth aspect of the invention can perform wavelength conversion with high efficiency by utilizing a nonlinear optical phenomenon that is manifested by inputting light of a predetermined wavelength into a highly nonlinear optical fiber.
The optical pulse compression apparatus according to the nineteenth aspect of the invention can perform optical pulse compression with high efficiency by utilizing a nonlinear optical phenomenon that is manifested by inputting light of a predetermined wavelength into a highly nonlinear optical fiber.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram schematically showing a refractive index profile of a first embodiment of a highly nonlinear optical fiber (hereinafter referred to as an optical fiber) according to the present invention.
This optical fiber has SiO ₂ (quartz glass) as a main component, the core region 10 including the central axis of the optical fiber, the first cladding region 11 provided on the outer periphery of the core region 10, and the outer periphery of the first cladding region 11. The second clad region 12 is provided on the second clad region 12.

  The core region 10 is formed so that the maximum refractive index is n1a, the first cladding region 11 is formed so that the minimum refractive index is n2a, and the second cladding region 12 has a refractive index n3a. It is formed as follows. The refractive indexes of these regions have a relationship of n1a> n3a> n2a. The radius from the center of the core region 10 (= the center of the optical fiber) to the position having the same refractive index as the refractive index n3a of the second cladding region 12 is defined as r (aa), and the center of the core region 10 When the radius from the core region 10 to the position having a refractive index having the same value as (n1a + n3a) / 2 is r (ba), the ratio r (ba) / r (aa) of these radii is 0. It is configured to be 8 or more.

  Thus, when the refractive index (n1a, n2a, n3a, respectively) of the core region 10, the first cladding region 11, and the second cladding region 12 of the optical fiber is a W-type structure such that n1a> n3a> n2a, high nonlinearity is achieved. Is obtained, and the dispersion slope at the signal light wavelength of 1550 nm is likely to be close to zero, and the radius ratio r (ba) / r (aa) with respect to the core region 10 is 0.8 or more. As a result, the dispersion value and dispersion slope for light having a shorter wavelength and longer wavelength than 1550 nm can be brought close to zero.

Further, the relative refractive index differences Δ1a and Δ2a and the radii r (aa) and r (ca) of the core region 10 and the first cladding region 11 of the optical fiber are adjusted, and various characteristics with respect to light having a wavelength of 1550 nm are 20 μm ^2. From the following effective area A _eff , chromatic dispersion value of −2 ps / nm / km or more +2 ps / nm / km or less, nonlinear coefficient of 6 / W / km or more, chromatic dispersion value for light of wavelength 1550 nm and 1550 nm By having a structure having a wavelength dispersion characteristic in which the absolute value of the difference from the wavelength dispersion value with respect to light having a wavelength of 100 nm is 2 ps / nm / km or less, it has a very good dispersion flat characteristic and is sufficient An optical fiber having a non-linearity can be provided.
In FIG. 1, the relative refractive index difference Δ1a is defined by the following equation (3).
Δ1a = {(n1a−n3a) / n3a} × 100 (3)
The relative refractive index difference Δ2a is defined by the above equation (1). The radius of the first cladding is r (ca).

  2 and 3 are graphs showing the influence of the radius ratio r (ba) / r (aa) on the core region 10 on the dispersion characteristics of the optical fiber. FIG. 2 shows optical fiber wavelengths from 1450 nm to 1650 nm when the ratio of radii r (ba) / r (aa) is 1, 0.9, 0.8, 0.7, 0.6, and 0.5, respectively. It is a graph which shows the change of dispersion | distribution in the range. FIG. 3 shows the relationship between the value obtained by subtracting the most negative dispersion value from the maximum dispersion value in FIG. 2 (hence, referred to as dispersion width) and the radius ratio r (ba) / r (aa). It is a graph.

  2 and 3, as the radius ratio r (ba) / r (aa) is smaller than 1, the dispersion value and dispersion slope for light having wavelengths shorter and longer than 1550 nm are further away from zero, and the dispersion width Becomes larger, the dispersion flat characteristic becomes worse. If the radius ratio r (ba) / r (aa) is 0.8 or more, the dispersion width of the optical fiber having the radius ratio r (ba) / r (aa) = 1, which is the optical fiber having the smallest dispersion width. Compared with, the difference in dispersion width is less than twice, so the dispersion flat characteristic is good. Therefore, the radius ratio r (ba) / r (aa) with respect to the core region 10 is desirably 0.8 or more.

  FIGS. 4 and 5 show refractive index profiles of optical fibers having radius ratios r (ba) / r (aa) = 0.8 and 0.6, respectively. In these figures, the refractive index profile shape of the core region 10 is trapezoidal, but the refractive index profile shape of the core region 10 of the optical fiber according to the present invention is not necessarily trapezoidal. When the radius ratio r (ba) / r (aa) with respect to 10 is 0.8 or more, the dispersion flat characteristic is good regardless of the refractive index profile shape of the core region 10.

In the optical fiber of the present embodiment, the ratio of radii r (ba) / r (aa) with respect to the core region 10 is set to 0.8 or more, and the relative refractive indexes of the core region 10 and the first cladding region 11 of the optical fiber. By adjusting the differences Δ1a and Δ2a and the radii r (aa) and r (ca), as various characteristics with respect to light having a wavelength of 1550 nm, an effective area A _eff of 20 μm ² or less and −2 ps / nm / km or more +2 ps / The optical fiber has a chromatic dispersion value of nm / km or less and a nonlinear coefficient of 6 / W / km or more.
The ratio r (ba) / r (aa) of the radius related to the core region 10 is set to 0.9 to 1.0, and the ratio r (ca) / r (aa) of the first cladding radius to the core radius is set to 1.8 to 2. .6, optical fibers of the present invention were manufactured at several relative refractive index differences Δ1a and Δ2a. At this time, Δ1a and Δ2a were adjusted so that the chromatic dispersion value and the dispersion slope for light having a wavelength of 1550 nm were both substantially zero. Table 1 shows Δ1a and Δ2a of the manufactured optical fibers and A _eff of the optical fiber with respect to light having a wavelength of 1550 nm.

As shown in Table 1, in order to obtain an effective area A _eff of 20 μm ² or less, the relative refractive index difference Δ1a of the core region 10 relative to the second cladding region 12 is set to 1.4% or more, and the second cladding region 12 relative to the second cladding region 12 is obtained. The relative refractive index difference Δ2a of one cladding region 11 is preferably set to −0.4% or less. Further, in order to obtain an optical fiber having a small A _eff and higher nonlinearity, and a dispersion value and dispersion slope at a signal light wavelength of 1550 nm close to zero, the core region 10 with respect to the second cladding region 12 of the optical fiber is used. The relative refractive index difference Δ1a of the first cladding region 11 with respect to the second cladding region 12 is set to −0.6% or less, and the relative refractive index difference Δ1a is set to 1.0% or more, more preferably 2.9% or more. Is preferable, and -1.0% or less is more preferable.

FIG. 6 is a diagram schematically showing a refractive index profile of the second embodiment of the optical fiber according to the present invention. This optical fiber has SiO ₂ (quartz glass) as a main component, the core region 20 including the central axis of the optical fiber, the first cladding region 21 provided on the outer periphery of the core region 20, and the outer periphery of the first cladding region 21. The second cladding region 22 provided on the outer periphery, the third cladding region 23 provided on the outer periphery of the second cladding region 22, and the fourth cladding 24 provided on the outer periphery of the third cladding region 23. .

  The core region 20 is formed so that the maximum refractive index is n1b, the first cladding region 21 is formed so that the minimum refractive index is n2b, and the second cladding region 22 has a refractive index n3b. The third cladding region 23 is formed to have a refractive index of n4b, and the fourth cladding region 24 is formed to have a refractive index of n5b. The refractive index of each of these regions is such that n1b ≧ n3b> n5b ≧ n4b> n2b. The radius from the center of the core region 20 to a position having the same refractive index as the refractive index n4b of the third cladding region 23 in the core region 20 is defined as r (ab), and from the center of the core region 20 to the core region 20 ( n1b + n4b) / 2, where r (bb) is a radius to a position having a refractive index that is the same value, the radius ratio r (bb) / r (ab) with respect to the core region should be 0.8 or more. It is.

  Thus, the refractive indexes (n1b, n2b, n3b, n4b, n5b, respectively) of the core region 20, the first cladding region 21, the second cladding region 22, the third cladding region 23, and the fourth cladding region 24 of the optical fiber are set to n1b. When a W + side core structure such that ≧ n3b> n5b ≧ n4b> n2b is obtained, an optical fiber having high nonlinearity can be obtained, and a dispersion slope at a signal light wavelength of 1550 nm can be easily obtained with a value close to zero. By setting the radius ratio r (bb) / r (ab) with respect to the core region 20 to 0.8 or more, the dispersion value and dispersion slope for light having a wavelength shorter and longer than 1550 nm can be close to zero. It becomes.

Further, the relative refractive index differences Δ1b, Δ2b, Δ3b, Δ4b and the radius r (ab) of the core region 20, the first cladding region 21, the second cladding region 22, and the fourth cladding region 24 of the optical fiber with respect to the third cladding region 23. , R (cb), r (db), r (eb) are adjusted, and various characteristics with respect to light having a wavelength of 1550 nm have an effective area A _eff of 20 μm ² or less and −2 ps / nm / km or more +2 ps / nm / The absolute value of the difference between the chromatic dispersion value of km or less, the nonlinear coefficient of 6 / W / km or more, the chromatic dispersion value for light having a wavelength of 1550 nm and the chromatic dispersion value for light having a wavelength 100 nm away from 1550 nm is 2 ps / nm. An optical fiber having a very good dispersion flat characteristic and sufficient nonlinearity is provided by having a chromatic dispersion characteristic of less than / km Kill.
In FIG. 6, the relative refractive index differences Δ1b, Δ3b, Δ4b are defined by the following equations (4), (5), (6).
Δ1b = {(n1b−n4b) / n4b} × 100 (4)
Δ3b = {(n3b−n4b) / n4b} × 100 (5)
Δ4b = {(n5b−n4b) / n4b} × 100 (6)
The relative refractive index difference Δ2b is defined by the equation (2). The radius of the first cladding is r (cb), the radius of the second cladding region is r (db), and the radius of the third cladding is r (eb).

  7 and 8 are graphs showing the influence of the radius ratio r (ba) / r (aa) on the core region 12 on the dispersion characteristics of the optical fiber. FIG. 7 shows optical fiber wavelengths from 1450 nm to 1650 nm when the ratio of radii r (ba) / r (aa) is 1, 0.9, 0.8, 0.7, 0.6, and 0.5, respectively. It is a graph which shows the change of dispersion | distribution in the range. FIG. 8 shows the relationship between the value obtained by subtracting the largest negative dispersion value from the maximum dispersion value in FIG. 7 (hence, referred to as dispersion width) and the radius ratio r (ba) / r (aa). It is a graph.

  7 and 8, as the radius ratio r (bb) / r (ab) is smaller than 1, the dispersion value and dispersion slope for light having a wavelength shorter and longer than 1550 nm move away from zero, and the dispersion width Becomes larger, the dispersion flat characteristic becomes worse. If the radius ratio r (bb) / r (ab) is 0.8 or more, the dispersion width of the optical fiber having the radius ratio r (bb) / r (ab) = 1, which is the optical fiber having the smallest dispersion width. Compared with, the difference in dispersion width is less than twice, so the dispersion flat characteristic is good. Therefore, it is desirable that the radius ratio r (bb) / r (ab) regarding the core region is 0.8 or more.

  Refractive index profiles of optical fibers having radius ratios r (bb) / r (ab) = 0.8 and 0.6 are shown in FIGS. In these figures, the refractive index profile shape of the core region 20 is a trapezoid, but the refractive index profile shape of the core region 20 of the optical fiber according to the present invention is not necessarily a trapezoid. When the radius ratio r (ba) / r (aa) with respect to 20 is 0.8 or more, the dispersion flat characteristic is good regardless of the refractive index profile shape of the core region 20.

In the optical fiber of the present embodiment, the radius ratio r (bb) / r (ab) with respect to the core region 20 is set to 0.8 or more, and further, the core region 20, the first cladding region 21, and the second cladding region 22 of the optical fiber. By adjusting the relative refractive index differences Δ1b, Δ2b, Δ3b, Δ4b and the radius ratios r (ab), r (cb), r (db), r (eb) of the fourth cladding region 24, the wavelength As various properties for light of 1550 nm, an effective area A _eff of 20 μm ² or less, a chromatic dispersion value of −2 ps / nm / km or more +2 ps / nm / km or less, a nonlinear coefficient of 6 / W / km or more, a wavelength An optical fiber having a wavelength dispersion characteristic in which the absolute value of the difference between the wavelength dispersion value for light having a wavelength of 1550 nm and the wavelength dispersion value for light having a wavelength 100 nm away from 1550 nm is 2 ps / nm / km or less. It has become a driver.
The ratio r (bb) / r (ab) of the radius with respect to the core region 20 is set to 0.9 to 1.0, and the ratio r (cb) / r (ab) of the first cladding radius to the core radius is set to 1.8 to 2. .6, the ratio r (db) / r (ab) of the second cladding radius to the core radius is 2.6 to 3.4, and the ratio r (eb) / r (ab) of the third cladding radius to the core radius. Was set to 4.0 or more, and the relative refractive index difference Δ4b was set to about 0.05%, and the optical fibers of the present invention at several relative refractive index differences Δ1b, Δ2b, Δ3b were manufactured. At this time, Δ1b, Δ2b, and Δ3b were adjusted so that the chromatic dispersion value and the dispersion slope with respect to light having a wavelength of 1550 nm were almost zero. Table 2 shows Δ1b, Δ2b, Δ3b of the manufactured optical fiber and A _eff of the optical fiber with respect to light having a wavelength of 1550 nm.

As shown in Table 2, in order to obtain an effective area A _eff of 20 μm ² or less, in the optical fiber of the present embodiment, in addition to the above configuration, the relative refractive index difference Δ1b of the core region 20 with respect to the third cladding region 23 Is 1.2% or more, the relative refractive index difference Δ2b of the first cladding region 21 with respect to the third cladding region 23 is −0.35% or less, and the relative refraction of the second cladding region 22 with respect to the third cladding region 23 It is preferable that the rate difference Δ3b is 0.2% or more and the relative refractive index difference Δ4b of the fourth cladding region 24 with respect to the third cladding region 23 is 0.05% or more.
Further, in order to make an optical fiber having a small A _eff and higher nonlinearity, and having a dispersion value and a dispersion slope at a signal light wavelength of 1550 nm close to zero, a core region for the third cladding region 23 of the optical fiber is used. 20 relative refractive index difference Δ1b is 1.5% or more, more preferably 3.0% or more, and relative refractive index difference Δ2b of the first cladding region 21 with respect to the third cladding region 23 is −0.5% or less, More preferably, it is −0.8% or less, and the relative refractive index difference Δ3b of the second cladding region 22 with respect to the third cladding region 23 is 0.3% or more, more preferably 0.7% or more. The relative refractive index difference Δ4b of the fourth cladding region 24 with respect to the region 23 is preferably 0.05% or more.

Next, the dispersion flat characteristic of the optical fiber of the present invention will be described in detail.
Optical fibers having different dispersion flat characteristics shown in Table 3 were produced. The refractive index profile of any optical fiber is the W + side core type of the second embodiment shown in FIG. For both fibers, r (bb) / r (ab) is approximately 0.9. The dispersion width in the wavelength range from 1450 nm to 1650 nm in Table 3 is a value obtained by subtracting the most negative dispersion value from the maximum dispersion value in this wavelength range as described above, and this is used as an index of dispersion flat characteristics. . FIG. 11 shows a plot of dispersion characteristics at wavelengths from 1450 nm to 1650 nm for the A2, A3, A5, A7, and A8 fibers among the optical fibers in Table 3.

As shown in Table 3 and FIG. 11, the optical fibers A3, A4, A5, A6, and A7 have a characteristic with respect to light having a wavelength of 1550 nm of −0.01 ps / nm ² / km or more and 0.01 ps / nm ² / km or less. It has a dispersion characteristic such that the wavelength of light further having a wavelength dispersion slope and having a wavelength dispersion slope of zero is at least one in the wavelength range of 1450 nm to 1650 nm. It becomes 2 ps / nm / km or less and has a good dispersion flat characteristic.

Therefore, the refractive index profile of the optical fiber is set as the second embodiment of the present invention, and the wavelength dispersion slope of −0.01 ps / nm ² / km or more and +0.01 ps / nm ² / km or less is used as the characteristic for light having a wavelength of 1550 nm. In addition, the optical fiber of the present invention having a dispersion characteristic such that at least one wavelength of light having a chromatic dispersion slope of zero is in the wavelength range of 1450 nm to 1650 nm has a dispersion flat characteristic. Is good. The same applies to not only the second embodiment of the present invention but also the optical fiber having the W-type refractive index profile according to the first embodiment.

  As described above, an optical fiber having a core region in which r (ba) / r (aa) is 0.8 or more, and having each characteristic, sufficient nonlinearity and very good dispersion flat characteristics. By using this optical fiber, it becomes possible to make optical amplifiers, wavelength converters, supercontinuum light generators, and the like have good characteristics.

It is a schematic diagram which shows the refractive index profile of 1st Embodiment of the optical fiber which concerns on this invention. It is a graph which shows the ratio of radius ratio r (ba) / r (aa) regarding the core area | region of the optical fiber of 1st Embodiment, and the dispersion characteristic of an optical fiber. It is a graph which shows the ratio of radius ratio r (ba) / r (aa) regarding a core area | region, and the dispersion width of the optical fiber of 1st Embodiment. In the optical fiber of 1st Embodiment, it is a schematic diagram which shows an example of the refractive index profile of the optical fiber whose radius ratio r (ba) / r (aa) = 0.8 regarding a core area | region. In the optical fiber of 1st Embodiment, it is a schematic diagram which shows an example of the refractive index profile of the optical fiber whose radius ratio r (ba) / r (aa) = 0.6 regarding a core area | region. It is a schematic diagram which shows the refractive index profile of 2nd Embodiment of the optical fiber which concerns on this invention. It is a graph which shows the ratio of the radius r (bb) / r (ab) regarding the core area | region of the optical fiber of 2nd Embodiment, and the relationship of the dispersion characteristic of an optical fiber. It is a graph which shows the ratio of radius ratio r (bb) / r (ab) regarding a core area | region, and the dispersion width of the optical fiber of 2nd Embodiment. In the optical fiber of 2nd Embodiment, it is a schematic diagram which shows an example of the refractive index profile of the optical fiber whose radius ratio r (bb) / r (ab) = 0.8 regarding a core area | region. In the optical fiber of 2nd Embodiment, it is a schematic diagram which shows an example of the refractive index profile of the optical fiber whose radius ratio r (bb) / r (ab) = 0.6 regarding a core area | region. It is a graph which illustrates the dispersion characteristic of the optical fiber of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10,20 ... Core area | region, 11, 21 ... 1st clad area | region, 12, 22 ... 2nd clad area | region, 23 ... 3rd clad area | region, 24 ... 4th clad area | region.

Claims (19)

A core region having a refractive index nla; a first cladding region provided on the outer periphery of the core region and having a refractive index n2a; and a second cladding region provided on the outer periphery of the first cladding region and having a refractive index n3a Having at least
The refractive index of each of these regions is n1a>n3a> n2a,
The radius from the center of the core region to the position having the same refractive index as the refractive index n3a in the core region is r (aa), and the refractive index is the same value as (n1a + n3a) / 2 in the core region from the center of the core region. An optical fiber having a core region where r (ba) / r (aa) is 0.8 or more, where r (ba) is a radius to a position having
As characteristics for light with a wavelength of 1550 nm,
An effective area A _eff of 20 μm ² or less,
A chromatic dispersion value of −2 ps / nm / km to +2 ps / nm / km,
Having a nonlinear coefficient of 6 / W / km or more,
In addition, as a wavelength dispersion characteristic, a high nonlinearity characterized in that an absolute value of a difference between a wavelength dispersion value for light having a wavelength of 1550 nm and a wavelength dispersion value for light having a wavelength 100 nm away from 1550 nm is 2 ps / nm / km or less Optical fiber.   The relative refractive index difference Δ1a of the core region with respect to the second cladding region is 1.0% or more, the relative refractive index difference Δ2a of the first cladding region with respect to the second cladding region is −0.4% or less, and 2. The highly nonlinear optical fiber according to claim 1, wherein a ratio r (ca) / r (aa) of the first cladding radius to the core radius is in a range of 1.8 to 2.6.   The relative refractive index difference Δ1a of the core region with respect to the second cladding region is 1.4% or more, the relative refractive index difference Δ2a of the first cladding region with respect to the second cladding region is −0.6% or less, and 2. The highly nonlinear optical fiber according to claim 1, wherein a ratio r (ca) / r (aa) of the first cladding radius to the core radius is in a range of 1.8 to 2.6.   The relative refractive index difference Δ1a of the core region with respect to the second cladding region is 2.9% or more, the relative refractive index difference Δ2a of the first cladding region with respect to the second cladding region is −1.0% or less, and 2. The highly nonlinear optical fiber according to claim 1, wherein a ratio r (ca) / r (aa) of the first cladding radius to the core radius is in a range of 1.8 to 2.6. A core region having a refractive index n1b, a first cladding region having a refractive index n2b provided on the outer periphery of the core region, and a second cladding region having a refractive index n3b provided on the outer periphery of the first cladding region. A third cladding region provided on the outer periphery of the second cladding region and having a refractive index n4b; and a fourth cladding region provided on the outer periphery of the third cladding region and having a refractive index n5b. ,
The refractive index of each of these regions is n1b ≧ n3b> n5b ≧ n4b> n2b,
A position having the same refractive index as the refractive index n4b from the center of the core region is defined as r (ab), and a position having a refractive index equal to (n1b + n4b) / 2 from the center of the core region to the core region. R (bb) is an optical fiber having a core region where r (bb) / r (ab) is 0.8 or more,
As characteristics for light with a wavelength of 1550 nm,
An effective area A _eff of 20 μm ² or less,
A chromatic dispersion value of −2 ps / nm / km to +2 ps / nm / km,
Having a nonlinear coefficient of 6 / W / km or more,
In addition, as a wavelength dispersion characteristic, a high nonlinearity characterized in that an absolute value of a difference between a wavelength dispersion value for light having a wavelength of 1550 nm and a wavelength dispersion value for light having a wavelength 100 nm away from 1550 nm is 2 ps / nm / km or less Optical fiber.   The relative refractive index difference Δ1b of the core region with respect to the third cladding region is 1.2% or more, the relative refractive index difference Δ2b of the first cladding region with respect to the third cladding region is −0.35% or less, The relative refractive index difference Δ3b of the second cladding region with respect to the third cladding region is 0.2% or more, the relative refractive index difference Δ4b of the fourth cladding region with respect to the third cladding region is 0.05% or more, The ratio r (cb) / r (ab) of the first cladding radius to the core radius is in the range of 1.8 to 2.6, and the ratio r (db) / r (ab) of the second cladding radius to the core radius is 2. 6. The non-linearity according to claim 5, wherein the ratio r (eb) / r (ab) of the third cladding radius to the core radius is 4.0 or more in the range of .6 to 3.4. Optical fiber.   The relative refractive index difference Δ1b of the core region with respect to the third cladding region is 1.5% or more, the relative refractive index difference Δ2b of the first cladding region with respect to the third cladding region is −0.5% or less, The relative refractive index difference Δ3b of the second cladding region with respect to the third cladding region is 0.3% or more, the relative refractive index difference Δ4b of the fourth cladding region with respect to the third cladding region is 0.05% or more, The ratio r (cb) / r (ab) of the first cladding radius to the core radius is in the range of 1.8 to 2.6, and the ratio r (db) / r (ab) of the second cladding radius to the core radius is 2. 6. The non-linearity according to claim 5, wherein the ratio r (eb) / r (ab) of the third cladding radius to the core radius is 4.0 or more in the range of .6 to 3.4. Optical fiber.   The relative refractive index difference Δ1b of the core region with respect to the third cladding region is 3.0% or more, the relative refractive index difference Δ2b of the first cladding region with respect to the third cladding region is −0.8% or less, The relative refractive index difference Δ3b of the second cladding region with respect to the third cladding region is 0.7% or more, the relative refractive index difference Δ4b of the fourth cladding region with respect to the third cladding region is 0.05% or more, The ratio r (cb) / r (ab) of the first cladding radius to the core radius is in the range of 1.8 to 2.6, and the ratio r (db) / r (ab) of the second cladding radius to the core radius is 2. 6. The non-linearity according to claim 5, wherein the ratio r (eb) / r (ab) of the third cladding radius to the core radius is 4.0 or more in the range of .6 to 3.4. Optical fiber. The wavelength of light having a wavelength dispersion slope of −0.01 ps / nm ² / km or more and 0.01 ps / nm ² / km or less as a characteristic with respect to light having a wavelength of 1550 nm and having a chromatic dispersion slope of zero, The highly nonlinear optical fiber according to any one of claims 1 to 8, which has a dispersion characteristic such that there is at least one in a wavelength range of 1450 nm to 1650 nm.   The highly nonlinear optical fiber according to any one of claims 1 to 9, wherein a stress applying portion structure is provided and has polarization maintaining ability. The highly nonlinear optical fiber according to claim 1, wherein fluorine is added to the core region together with GeO ₂ .   The highly nonlinear optical fiber according to claim 11, wherein the fluorine concentration is 1% by mass or more.   The chromatic dispersion value in the light with a wavelength of 1550 nm changes almost linearly along the longitudinal direction of the fiber, and the change is that the chromatic dispersion value changes from a positive value to a negative value via zero. The highly nonlinear optical fiber according to claim 1, wherein the optical fiber is highly nonlinear.   A method for producing the highly nonlinear optical fiber according to claim 1, wherein a core glass rod to be a core region is synthesized by a VAD method or an OVD method, and an outer periphery of the synthesized core glass rod. Then, a glass layer to be the first cladding region is synthesized on the outer periphery of the core glass rod, and the glass layers to be the cladding regions provided on the outer periphery are sequentially synthesized to sequentially synthesize the optical fiber mother. A core glass rod synthesized in the step of manufacturing a material and then drawing the optical fiber preform to produce a highly nonlinear optical fiber, and removing a part of the outer periphery of the core glass rod (N1c + n2c) in the core glass rod, where n1c is the refractive index of the central portion of the core and n2c is the refractive index of the outermost peripheral portion before the outer periphery of the core glass rod is removed. When the position having the same refractive index as 2 is r (bc), {r (bc) / core glass rod radius} is equal to or more than 0.8 on the outer periphery of the core glass rod. A method for producing a highly nonlinear optical fiber, wherein the portion is removed.   In the step of heating and drawing the optical fiber preform, the chromatic dispersion value in the light having a wavelength of 1550 nm is along the longitudinal direction of the fiber by drawing so that the outer diameter of the optical fiber is gradually reduced or expanded along the longitudinal direction. A highly nonlinear optical fiber is obtained in which the chromatic dispersion value changes from a positive value to a negative value via zero through a change that is substantially linearly changed. 14. A method for producing a highly nonlinear optical fiber according to 14.   The high nonlinear optical fiber according to claim 1, and at least a pumping light source that supplies pumping light having a predetermined wavelength λp to the high nonlinear optical fiber. A supercontinuum light generating device characterized in that supercontinuum light is generated using a nonlinear optical phenomenon expressed by inputting a predetermined wavelength λp into the continuum.   14. An optical amplifier using the highly nonlinear optical fiber according to claim 1, wherein a nonlinear optical phenomenon expressed by inputting light of a predetermined wavelength into the highly nonlinear optical fiber is used. An optical amplifier characterized by comprising:   14. A wavelength converter using the highly nonlinear optical fiber according to claim 1, wherein a nonlinear optical phenomenon expressed by inputting light of a predetermined wavelength into the highly nonlinear optical fiber is used. A wavelength converter characterized by having An optical pulse compression device using the highly nonlinear optical fiber according to any one of claims 1 to 13, wherein a nonlinear optical phenomenon expressed by inputting light of a predetermined wavelength into the highly nonlinear optical fiber. An optical pulse compression device characterized by being used.

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