JP2006515485A - Chromatic dispersion compensation module - Google Patents

Abstract

The field of the invention is that of chromatic dispersion compensation modules and methods of configuring chromatic dispersion compensation modules. The configuration method includes an optimization step that is to reduce the original quality criteria. The compensating optical fiber of the module has a chromatic dispersion that is less than a first threshold and that is sufficiently negative with respect to a quality criterion that should be less than a second threshold.

Description

  The field of the invention is that of chromatic dispersion compensation modules. The terms “attenuation” and “attenuation coefficient” are used interchangeably with respect to optical fiber.

  In some wavelength division multiplexing (WDM) optical fiber transmission networks, including line optical fibers on which optical signals propagate, there is no means for compensating for the chromatic dispersion of the line optical fibers. When the bit rate is small, for example, 2.5 gigabits per second (Gbit / s) per channel, it is not necessary to compensate for the chromatic dispersion of the line optical fiber. However, as the bit rate increases to a large value, for example, 10 Gbit / s per channel, it becomes necessary to compensate for the chromatic dispersion and dispersion gradient of the line optical fiber. Line optical fibers generally have positive chromatic dispersion and positive dispersion slope. As a result, the chromatic dispersion compensating optical fiber generally has a negative chromatic dispersion and a negative dispersion gradient. The chromatic dispersion compensating optical fiber can be integrated into the chromatic dispersion compensating module. The spectral range in which chromatic dispersion is to be compensated can include one or more of bands C, L, and S.

  The optical signal propagates in the chromatic dispersion compensating optical fiber. When an optical signal propagates through a chromatic dispersion compensating optical fiber, the optical signal is likely to deteriorate, and is affected by, for example, a decrease in signal-to-noise ratio or an increase in nonlinear effects. A chromatic dispersion compensation module for compensating the chromatic dispersion of one segment of a line optical fiber, usually several tens of kilometers (km) in length, generally has a relatively high insertion loss on the order of several decibels (dB). Due to the magnitude of its own insertion loss, the chromatic dispersion compensation module is generally installed in the middle of the two-stage amplifier system, ie between the two amplifiers.

  Because the two-stage amplifier system has a good optical signal-to-noise ratio and gain over a flat spectrum, the two-stage amplifier system has a high gain that produces large optical power at the output of the first amplifier. Presents an amplifier and exhibits a loss between the two amplifiers at a fixed level.

A chromatic dispersion compensating optical fiber integrated into the chromatic dispersion compensating module makes it less sensitive to non-linear effects than a single mode optical fiber, for example, very large effective on the order of 80 square micrometers (μm ² ) It is a multimode optical fiber having a high-order mode (HOM, High-Order Mode) having an area. However, nevertheless, HOM multimode optical fibers have some sensitivity to non-linear effects. In order to maintain good optical signal transmission quality, it can be beneficial to limit the optical power input into the HOM multimode chromatic dispersion compensating optical fiber. In order to achieve this, an attenuator can be installed between the first amplifier and the chromatic dispersion compensation module. The attenuator also controls gain flatness across the spectrum. The attenuator is either by a wavelength routing component or by any other optical component that has a loss and thus can limit the input of optical power to the chromatic dispersion compensation module, such as an attenuator. Can be replaced.

  The problem is to produce a chromatic dispersion compensation module that provides the best possible quality. The cost of a chromatic dispersion compensation module based on a HOM multimode compensating optical fiber is relatively high. This is because this cost includes the cost of mode converters installed at the upstream and downstream ends of the HOM multimode compensating optical fiber. However, because of the very low negative value of the chromatic dispersion of the compensating optical fiber and the much higher ability of HOM multimode fiber with a very large effective area to resist non-linear effects, this kind of The compensation module may be more effective than a compensation module based on a single mode compensating optical fiber.

  One prior art compensation module is able to achieve a sufficiently high chromatic dispersion to dispersion slope ratio to compensate not only for chromatic dispersion but also dispersion slope of the line optical fiber, so Based on the use of a HOM multimode compensating optical fiber that does not have a low negative value. The disadvantage of this first prior art is that it does not fully take advantage of the very low negative value of chromatic dispersion that a HOM multimode optical fiber can achieve. Another disadvantage of this first prior art is that this first prior art has good performance in terms of insertion loss, but its poor multipath interference (MPI) performance. Using a Bragg grating converter for the compensating optical fiber has the advantage of reducing insertion loss, but also has the disadvantage of insufficient MPI. In conclusion, improved insertion loss degrades the ability to resist non-linear effects.

  The second prior art compensation module provides a chromatic dispersion emergency to obtain a sufficiently high chromatic dispersion to dispersion slope ratio for the compensation optical line so as to compensate not only the chromatic dispersion but also the dispersion slope of the line optical fiber. Based on the use of a combination of a HOM multimode compensating optical fiber having a very low negative value and a single mode compensating optical fiber. One disadvantage of this prior art is the complex design of this second prior art and the resulting complexity of the process of manufacturing the compensation module. Another disadvantage is that this second technique does not provide compensation in a very broad spectral band. A further disadvantage is that this second prior art combines the HOM multimode compensating optical fiber with a single mode compensating optical fiber having a much smaller effective area, resulting in the essential nature of the HOM multimode compensating optical fiber. The advantage, that is, the loss of its large effective area to at least some degree. Furthermore, a large loss occurs at the connection between the HOM multimode compensating optical fiber and the single mode compensating optical fiber, which further increases the already large insertion loss. Certainly, the presence of a connector is unavoidable, and this is not the case at the junction between two HOM multimode compensating optical fibers. In conclusion, improving the ability to resist non-linear effects increases module complexity and degrades insertion loss.

  An object of the present invention is to propose a high-quality chromatic dispersion compensation module that fully utilizes the advantages of a HOM multimode optical fiber. For this reason, the compensation module of the present invention does not include any single mode optical fiber. But questions arise. That is, how the quality of the chromatic dispersion compensation module is evaluated.

  Prior art methods for improving the quality of the compensation module are based on improving only one aspect of the parameters that partially represent the quality of the compensation module. Improving a parameter that partially represents the quality of the compensation module by one side has two consequences, whether the parameter is insertion loss or non-linear phase. First, this improvement increases the cost of the compensation module. Second, this improvement tends to degrade another parameter that partially represents the quality of the compensation module, so that the quality of the compensation module is not improved as much as desired, and perhaps only slightly. Or not improved at all.

  The inventive method for improving the quality of the compensation module is completely different. First, the method of the present invention creates a quality criterion that generally represents the quality of the compensation module, and integrates the contribution of insertion loss and the contribution of nonlinear effects with appropriate weighting. The contribution of insertion loss is related to the complete compensation of the line optical fiber, while the contribution of the nonlinear effect is related to the nonlinear phase but is separated from this nonlinear phase. Except for being reflected in the standard, it corresponds to the conventional insertion loss. The non-linearity criterion is obtained by simplification with a reasonable determination of the non-linear phase in order to take into account the constant nature of the loss between the two amplifiers of the two-stage amplifier system. Optimizing this new quality criterion will greatly improve insertion loss without excessively degrading the ability to resist non-linear effects, thus improving the overall quality of the compensation module, or Either significantly improve the ability to resist non-linear effects without excessively degrading the insertion loss, and thus improve the overall quality of the compensation module.

  According to the first aspect of the present invention, the quality of the compensation module of the present invention measured by the above-described novel quality criterion is high. The number of core segments in the core of the compensating optical fiber to obtain not only a very low negative value for chromatic dispersion, but also a ratio of chromatic dispersion to dispersion slope that is not only sufficiently large but also highly linear with wavelength Is preferably relatively high. In applications with relatively few channels in the spectral band where linearity can be sacrificed to some degree, compensating optical fibers where the core includes a small number of core segments are acceptable.

  According to a second aspect of the invention, the compensation module of the invention has a very low negative value of chromatic dispersion and a ratio of chromatic dispersion to dispersion slope that has not only high but also good linearity as a function of wavelength. The core uses at least one compensating optical fiber that includes multiple core segments. The core segment is preferably rectangular, as in the example described below. Nevertheless, the core segments can also be triangular or alpha-shaped; similarly, some core segments can have one specific shape and other core segments can have different shapes. it can.

  Accordingly, a first aspect of the present invention provides a method of configuring a compensation module, and one compensation module is suitable for compensating a standard single mode line optical fiber (SMF), and the other compensation module is Two compensation modules suitable for compensating non-zero dispersion-shifted single mode line optical fiber (NZ-DSF) are proposed. Therefore, the second aspect of the present invention is that one compensation module is suitable for compensating a standard single mode line optical fiber, and the other compensation module is a non-zero dispersion shifted single mode line light. Two compensation modules suitable for compensating the fiber are proposed.

かつ、ここで、Ｄ_ＤＣＭは、回線光ファイバの累積分散の負を呈し、前記モジュールは、非線形位相の効果を表し、かつワット×デシベル当たりの１０^−６キロメータ（ｋｍ／Ｗ・ｄＢ）で表された非線形性判定基準ＮＬＣを有するように構成され、ここで、

であり、
前記モジュールは、ｄＢで表された品質判定基準ＣＱを呈するように構成され、ここで、
ＣＱ＝ＩＬ＋１０ｌｏｇＮＬＣ
であり、
前記構成方法は、前記モジュールを最適化するための最適化工程を含み、前記最適化工程は、品質判定基準を低減することにある。 In a first aspect of the invention, a method for configuring a chromatic dispersion compensation module is provided,
The module is
An enclosure including input and output terminals;
A high-order mode chromatic dispersion compensating optical line installed inside the enclosure and disposed between the input terminal and the output terminal. Including a plurality of HOM multimode chromatic dispersion compensating optical fibers in series and no single mode optical fiber;
The module further includes
An input mode converter installed between the input terminal and the compensation optical line for converting the fundamental mode to the higher order mode;
An output mode converter installed between the compensation optical line and the output terminal and configured to convert the higher-order mode into a fundamental mode;
The module is configured to be inserted using a input terminal and an output terminal into a transmission line including a single mode line optical fiber configured to transmit information in a use spectrum region;
The input terminal and the input mode converter both introduce an input loss Γ _in expressed in dB into the transmission line,
The output terminal and the output mode converter both introduce an output loss Γ _out expressed in dB into the transmission line,
An additional connection between the compensating optical fibers, if present, introduces a connection loss Γ _inter , expressed in dB, into the transmission line together,
Compensating optical fiber or series of compensating optical fibers has an average attenuation coefficient α _DCF expressed in decibels per kilometer (dB / km) at a wavelength of 1,550 nanometers (nm), nanometers × picoseconds per kilometer Average chromatic dispersion D _DCF expressed in (ps / nm · km) and negative, average dispersion slope S _DCF expressed in square nanometers × picoseconds per kilometer (ps / nm ² · km) and negative Average chromatic dispersion to dispersion slope ratio D _DCF / S _DCF in nm, average performance defined as -D _DCF / α _DCF expressed in nanometers × picosecond per decibel (ps / nm · dB) Expressed as the exponent FOM _DCF , the mean effective area A _eff expressed in μm ² , and ^10-20 square meters per watt (m ² / W) Presents a plurality of average parameters, including an average second order coefficient n ₂ of refractive index as a function of intensity,
The ratio of average chromatic dispersion to dispersion slope is the ratio between average chromatic dispersion and average dispersion slope,
Average figure of merit is the negative of the ratio between average chromatic dispersion and average attenuation coefficient,
In the case of a single compensating optical fiber, the average attenuation coefficient is treated together with the corresponding attenuation coefficient of the single compensating optical fiber, and in the case of a series of compensating optical fibers, the average attenuation coefficient is Corresponding attenuation for each of the various fibers weighted by the individual contribution of the various compensating optical fibers to the total series length of the compensating optical fiber plus the ratio of the splice loss divided by the total length Equal to the sum of the coefficients,
In the case of a single compensating optical fiber, each of the other average parameters is treated together with the corresponding parameter of the single compensating optical fiber, and in the case of a series of compensating optical fibers, Each of the average parameters is an arithmetic average of the corresponding parameters of the various compensating optical fibers when weighted by the individual lengths of the various compensating optical fibers,
The module is configured to exhibit an insertion loss IL expressed in dB, where

And where D _DCM is the negative of the dispersion dispersion of the line optical fiber, the module represents the effect of nonlinear phase and is expressed in 10 ⁻⁶ kilometer per watt × decibel (km / W · dB). Is configured to have a non-linearity criterion NLC, wherein

And
The module is configured to exhibit a quality criterion CQ expressed in dB, where:
CQ = IL + 10log NLC
And
The configuration method includes an optimization step for optimizing the module, and the optimization step is to reduce a quality criterion.

かつ、ここで、Ｄ_ＤＣＭ＝−１，３６０ｐｓ／ｎｍであり、
前記モジュールは、非線形位相の効果を表し、かつ１０^−６ｋｍ／Ｗ・ｄＢで表された非線形性判定基準ＮＬＣを有し、ここで、

であり、
モジュールは、ｄＢで表された品質判定基準ＣＱを有し、ここで、
ＣＱ＝ＩＬ＋１０ｌｏｇＮＬＣ
であり、かつ、
補償光ファイバまたは直列の補償光ファイバの組は、第１に、−２００ｐｓ／ｎｍ・ｋｍよりも低い負の平均波長分散を呈し、第２に、２４０ｎｍから４００ｎｍまでの範囲の平均波長分散対分散勾配の比を呈し、かつ第３に、９．５ｄＢ未満である品質判定基準に対して十分に負である平均波長分散を呈する。 In a first aspect of the invention, a chromatic dispersion compensation module is also provided for compensating a standard single mode line optical fiber, the chromatic dispersion compensation module comprising:
An enclosure including input and output terminals;
The higher-order mode chromatic dispersion compensation optical line is disposed in the enclosure and disposed between the input terminal and the output terminal. Including a HOM multimode chromatic dispersion compensating optical fiber and no single mode optical fiber;
The chromatic dispersion compensation module
An input mode converter installed between the input terminal and the compensation optical line for converting the fundamental mode to the higher order mode;
An output mode converter installed between the compensating optical line and the output terminal for converting the higher order mode into a fundamental mode, wherein the module is a standard configured to transmit information in the use spectrum region It is configured to be inserted into a transmission line including a single mode line optical fiber using an input terminal and an output terminal,
The input terminal and the input mode converter both introduce an input loss Γ _in expressed in dB into the transmission line,
The output terminal and the output mode converter both introduce an output loss Γ _out expressed in dB into the transmission line,
An additional connection between the compensating optical fibers, if present, introduces a connection loss Γ _inter , expressed in dB, into the transmission line together,
The set of compensating optical fibers or series compensating optical fibers has an average chromatic dispersion D that is expressed as an average attenuation coefficient α _DCF expressed in dB / km, ps / nm · km, and negative at a wavelength of 1,550 nm. _DCF , expressed in ps / nm ² · km and negative, average dispersion slope S _DCF , ratio of average chromatic dispersion to dispersion slope, expressed in nm D _DCF / S _DCF , expressed in ps / nm · dB The average figure of merit FOM _DCF defined as -D _DCF / α _DCF , the average effective area A _eff expressed in μm ² , and the average refractive index 2 as a function of the intensity expressed in 10 ⁻²⁰ m ² / W Presents a plurality of average parameters, including the order coefficient n ₂ ,
The ratio of average chromatic dispersion to dispersion slope is the ratio between average chromatic dispersion and average dispersion slope,
Average figure of merit is the negative of the ratio between average chromatic dispersion and average attenuation coefficient,
In the case of a single compensating optical fiber, the average attenuation coefficient is treated together with the corresponding attenuation coefficient of the single compensating optical fiber, and in the case of a series of compensating optical fibers, the average attenuation coefficient is Corresponding attenuation for each of the various fibers weighted by the individual contribution of the various compensating optical fibers to the total series length of the compensating optical fiber plus the ratio of the splice loss divided by the total length Equal to the sum of the coefficients,
In the case of a single compensating optical fiber, each of the other average parameters is treated together with the corresponding parameter of the single compensating optical fiber, and in the case of a series of compensating optical fibers, Each of the average parameters is an arithmetic average of the corresponding parameters of the various compensating optical fibers when weighted by the individual lengths of the various compensating optical fibers,
The module has an insertion loss IL expressed in dB, where

And where D _DCM = -1,360 ps / nm,
The module has a non-linearity criterion NLC representing the effect of non-linear phase and expressed in 10 ⁻⁶ km / W · dB, where

And
The module has a quality criterion CQ expressed in dB, where:
CQ = IL + 10log NLC
And
Compensating optical fibers or series of compensating optical fibers firstly exhibit a negative average chromatic dispersion lower than −200 ps / nm · km, and secondly average chromatic dispersion versus dispersion in the range from 240 nm to 400 nm. It exhibits a gradient ratio, and third, an average chromatic dispersion that is sufficiently negative with respect to a quality criterion that is less than 9.5 dB.

かつ、ここで、Ｄ_ＤＣＭ＝−６８０ｐｓ／ｎｍであり、
モジュールは、非線形位相の効果を表し、かつ１０^−６ｋｍ／Ｗ・ｄＢで表された非線形性判定基準ＮＬＣを有し、ここで、

であり、
モジュールは、ｄＢで表された品質判定基準ＣＱを有し、ここで、
ＣＱ＝ＩＬ＋１０ｌｏｇＮＬＣ
であり、かつ、
補償光ファイバまたは直列の補償光ファイバの組は、第１に、−２５０ｐｓ／ｎｍ・ｋｍよりも低い負の平均波長分散を呈し、第２に、５．５ｄＢ未満である品質判定基準に対して十分に負である平均波長分散を呈する。 In a first aspect of the invention, a chromatic dispersion compensation module is further provided for compensating a non-zero dispersion shifted single mode line optical fiber, the chromatic dispersion compensation module comprising:
An enclosure including an input terminal (41) and an output terminal;
A high-order mode chromatic dispersion compensating optical line installed in the enclosure and disposed between the input terminal and the output terminal. The high-order mode chromatic dispersion compensating optical line includes one or a plurality of HOM multiples. Mode chromatic dispersion compensating optical fiber in series and no single mode optical fiber,
This chromatic dispersion compensation module
An input mode converter installed between the input terminal and the compensation optical line for converting the fundamental mode to the higher order mode;
An output mode converter installed between the compensation optical line and the output terminal for converting the higher order mode into a fundamental mode;
The module is inserted, using an input terminal and an output terminal, into a transmission line including a single-mode non-zero (at 1,550 nm) dispersion-shifted line optical fiber configured to transmit information in the used spectral region Configured as
The input terminal and the input mode converter both introduce an input loss Γ _in expressed in dB into the transmission line,
The output terminal and the output mode converter both introduce an output loss Γ _out expressed in dB into the transmission line,
An additional connection between the compensating optical fibers, if present, introduces a connection loss Γ _inter , expressed in dB, into the transmission line together,
The set of compensating optical fibers or series compensating optical fibers has an average chromatic dispersion D that is expressed as an average attenuation coefficient α _DCF expressed in dB / km, ps / nm · km, and negative at a wavelength of 1,550 nm. _DCF , expressed in ps / nm ² · km and negative, average dispersion slope S _DCF , ratio of average chromatic dispersion to dispersion slope, expressed in nm D _DCF / S _DCF , expressed in ps / nm · dB Average figure of merit FOM _DCF defined as -D _DCF / α _DCF , average effective area A _eff expressed in μm ² , and average refractive index as a function of intensity expressed as 10 ⁻²⁰ m ² / W Presents a plurality of average parameters, including a second order coefficient n ₂ ,
The ratio of average chromatic dispersion to dispersion slope is the ratio between average chromatic dispersion and average dispersion slope,
Average figure of merit is the negative of the ratio between average chromatic dispersion and average attenuation coefficient,
In the case of a single compensating optical fiber, the average attenuation coefficient is treated together with the corresponding attenuation coefficient of the single compensating optical fiber, and in the case of a series of compensating optical fibers, the average attenuation coefficient is Corresponding attenuation for each of the various fibers weighted by the individual contribution of the various compensating optical fibers to the total series length of the compensating optical fiber plus the ratio of the splice loss divided by the total length Equal to the sum of the coefficients,
In the case of a single compensating optical fiber, each of the other average parameters is treated together with the corresponding parameter of the single compensating optical fiber, and in the case of a series of compensating optical fibers, Each of the average parameters is an arithmetic average of the corresponding parameters of the various compensating optical fibers when weighted by the individual lengths of the various compensating optical fibers,
The module has an insertion loss IL expressed in dB, where

And where D _DCM = −680 ps / nm,
The module has a non-linearity criterion NLC representing the effect of non-linear phase and expressed in 10 ⁻⁶ km / W · dB, where

And
The module has a quality criterion CQ expressed in dB, where:
CQ = IL + 10log NLC
And
Compensating optical fibers or series of compensating optical fibers first exhibit a negative average chromatic dispersion lower than −250 ps / nm · km, and secondly for a quality criterion that is less than 5.5 dB. It exhibits an average chromatic dispersion that is sufficiently negative.

  Although not very appropriate in situations of use with amplification and compensation systems other than the two-stage amplification and compensation system described above, quality criteria remain valid and useful. The present invention is not limited to a two-stage amplification and compensation system of the type described above. The very low and thus very good quality criteria obtained with the compensation module of the present invention is the use of the compensation module of the present invention in an amplification and compensation system comprising only one amplifier and no attenuator. In this case, the compensation module of the present invention is installed downstream of the amplifier. This means that the amplifier includes only one amplifier, either with an attenuator between the amplifier and the compensation module, or without the attenuator, with a compensation module upstream of the amplifier. And also in compensation systems.

In a second aspect of the invention, a chromatic dispersion compensation module is further provided for compensating a standard single mode line optical fiber, the chromatic dispersion compensation module comprising:
An enclosure including input and output terminals;
A high-order mode chromatic dispersion compensating optical line installed in the enclosure and disposed between the input terminal and the output terminal. The high-order mode chromatic dispersion compensating optical line includes one or a plurality of chromatic dispersion compensating optical lines in series. Including a HOM multimode chromatic dispersion compensating optical fiber and no single mode optical fiber;
This chromatic dispersion compensation module
An input mode converter installed between the input terminal and the compensation optical line for converting the fundamental mode to the higher order mode;
An output mode converter installed between the compensation optical line and the output terminal for converting the higher order mode into a fundamental mode;
The module is configured to be inserted using a input terminal and an output terminal into a transmission line including a standard single mode line optical fiber configured to transmit information in a use spectrum region; and
At least one of the compensating optical fiber or the series compensating optical fiber has a core having at least five core segments, and the optical fiber having a core having at least five core segments, to which a core cladding is added. Simultaneously has a negative chromatic dispersion lower than −300 ps / nm · km and a ratio of chromatic dispersion to dispersion slope greater than 200 nm at a wavelength of 1,550 nm.

In a second aspect of the invention, a chromatic dispersion compensation module is further provided for compensating a non-zero dispersion shifted single mode line optical fiber, the chromatic dispersion compensation module comprising:
An enclosure including an input terminal and an output terminal;
A higher-order mode chromatic dispersion compensating optical line installed in the enclosure and disposed between the input terminal and the output terminal. The higher-order mode chromatic dispersion compensating optical line includes one or a plurality of chromatic dispersion compensating optical lines in series. Including a HOM multimode chromatic dispersion compensating optical fiber and no single mode optical fiber;
This chromatic dispersion compensation module
An input mode converter installed between the input terminal and the compensation optical line for converting the fundamental mode into the higher order mode;
An output mode converter installed between the compensation optical line and the output terminal for converting the higher order mode into a fundamental mode;
The module is inserted into a transmission line including a single-mode non-zero (at 1,550 nm) dispersion shifted line optical fiber configured to transmit information in the used spectral region using an input terminal and an output terminal. And
At least one of the compensating optical fiber or the compensating optical fiber in series has a core comprising at least four core segments, the core having a core comprising at least four core segments, wherein a core cladding is added to the core. The fiber has simultaneously a negative chromatic dispersion lower than −300 ps / nm · km and a ratio of chromatic dispersion to dispersion slope greater than 80 nm at a wavelength of 1,550 nm.

  The second aspect of the invention is not limited to a two-stage amplification and compensation system of the type described above.

  The invention will be more clearly understood and other features and advantages will become apparent in light of the following description and examples provided by way of example.

  The parameters and criteria used throughout the remainder of the specification are defined next. There are two situations to consider. Either the module contains a single compensating optical fiber with parameters, or the module contains a series of compensating optical fibers that make up a set of fibers with average parameters. For simplicity, in all of FIGS. 1-9, the compensation module is considered to include only one compensating optical fiber, and the qualifier “average” in the parameter definition can be ignored. .

  When the compensation module includes only one compensation optical fiber, the module has the great advantage that its design and assembly are simplified.

  The compensation module was taken from multiple compensation optical fibers from the same group, i.e. from the exact same compensation optical fiber, or from different production times of the same compensation optical fiber, and thus caused by manufacturing tolerances When including any of multiple segments that have undergone slight differences, and once the optical fiber is aligned and assembled together, the fiber is highly accurate, despite wider assembly tolerances. It provides some defined characteristics, such as line optical fiber dispersion slope, or ratio of chromatic dispersion to dispersion slope. The same group of compensating optical fibers are preferably connected together directly, but these fibers can be connected together using a connector. The compensation module has the advantages of simplicity of design and improvements to some of the characteristics of the compensation module.

  When the compensation module includes a plurality of separate compensated optical fibers that are matched and assembled together, the compensating optical fibers span a very broad spectral band, i.e. at least of spectral bands S, C, and L. Provides compensation over two. The S, C, and L spectral bands range from about 1,460 nanometers (nm) to about 1,530 nm, from about 1,530 nm to about 1,565 nm, and from about 1,565 nm to about 1,615 nm, respectively. However, the compensation module has the disadvantage that it is difficult to design and produce. In the second prior art module, the overly wide range of compensation at the same time, i.e. over multiple spectral bands, is disturbed by the excessively high levels of bending and micro-bending losses provided at large wavelengths. The use of a combination of HOM multimode and single-mode compensating optical fibers with a positive sign of dispersion slope and a very large effective area resulting from normal bending and microbending performance is This is different from the case of using a multimode optical fiber. For this type of combination of multimode HOM compensated optical fiber with single mode fiber, the selected HOM multimode, either single mode compensated fiber or standard single mode or non-zero dispersion shift compensated fiber The optical fiber's figure of merit must be much higher than the figure of merit required in the absence of single-mode compensated optical fiber for comparable values of quality criteria and is therefore more difficult to achieve It becomes.

  Consider two fibers with individual lengths l1 and l2, attenuation factors a1 and a2 per unit length, and a splice loss pc between the two fibers. The average attenuation coefficient am per unit length of the series compensating optical fiber has the value am = (al × 11 + a2 × l2 + pc) / (l1 + l2). This type of calculation of the average attenuation coefficient can be generalized to more than two compensating optical fibers in series. Only the average attenuation coefficient, which is a special case of optical fiber parameters, is calculated in this way and all other average parameters are calculated in other ways.

Consider two optical fibers with individual lengths l1 and l2 and individual chromatic dispersions c1 and c2 per unit length. The average chromatic dispersion cm per unit length of the series compensating optical fiber has the value cm = (c1 × l1 + c2 × l2) / (l1 + l2). This type of average chromatic dispersion calculation can be generalized to more than two compensating optical fibers in series. Except for average attenuation coefficient, ratio of average chromatic dispersion to dispersion slope, and average figure of merit, all other average parameters: average chromatic dispersion, average effective area, and function of the intensity of the optical signal propagating in the optical fiber The average second order coefficient of the refractive index of the optical fiber as shown as conventional n ₂ is calculated in this way. The ratio of average chromatic dispersion to dispersion slope is the ratio between the average chromatic dispersion and the average dispersion slope. The average figure of merit is the negative of the ratio between the average chromatic dispersion and the average attenuation coefficient.

  For example, in the case of two compensating optical fibers in series, called optical fiber a and optical fiber b, there is an accurate nonlinearity criterion formula. The various parameter indices a and b represent those parameters for optical fibers a and b, respectively.

である正確な式は、以下の如くである。

In the case of two compensating optical fibers in series,

The exact formula is as follows:

  However, the approximate expression obtained from the average parameter of the compensation optical line yields excellent results that are very similar to the results obtained using the exact expression. This is the reason why the approximate expression is used.

The chromatic dispersion compensation module includes a chromatic dispersion compensating optical line and an enclosure having an input terminal and an output terminal. A higher-order mode chromatic dispersion compensating optical line includes one or a plurality of HOM multimode chromatic dispersion compensating optical fibers in series, does not include any single mode optical fiber, is installed in an enclosure, and Arranged between output terminals. The input mode converter converts the fundamental mode into the higher order mode and is installed between the input terminal and the compensation optical line. The output mode converter converts the higher order mode into the basic mode and is installed between the compensation optical line and the output terminal. The module is intended to be connected, using input and output terminals, to a transmission line including a single mode line optical fiber configured to transmit information in the use spectrum region. Both the input terminal and the input mode converter introduce an input loss Γ _in expressed in dB into the transmission line. The output terminal and the output mode converter both introduce an output loss Γ _out expressed in dB into the transmission line. If the compensation line includes a plurality of compensation optical fibers in series, the additional connection between the compensation optical fibers introduces a connection loss Γ _inter expressed in dB into the transmission line together.

A compensation optical fiber or a series of compensation optical fibers in series is represented by an average attenuation coefficient α _DCF expressed in dB / km, ps / nm · km, and negative average chromatic dispersion D _DCF , ps / nm ² · The average dispersion slope S _DCF expressed in km and negative, the ratio of the average chromatic dispersion to the dispersion slope expressed in nm D _DCF / S _DCF , ps / nm · dB, and (D _DCF itself is negative Gives a value that is positive so) -D _DCF / α _DCF equals the average figure of merit FOM _DCF , average effective area A _eff expressed in μm ² , and intensity expressed in 10 ⁻²⁰ m ² / W With an average parameter at a wavelength of 1,550 nanometers (nm), including an average secondary refractive index coefficient n ₂ as a function of As already explained above, first, in the case of a single compensating optical fiber, the average attenuation coefficient is treated together with the corresponding attenuation coefficient of the single compensating optical fiber, and the series compensating optical fiber The average attenuation coefficient is weighted by the individual contribution of the various compensating optical fibers to the total series length of the compensating optical fiber plus the ratio of the splice loss divided by the total length. Is equal to the sum of the corresponding attenuation factors of each of the various fibers, and, secondly, in the case of a single compensating optical fiber, each of the other average parameters is equal to the corresponding parameter of the single compensating optical fiber. In the case of a set of compensating optical fibers in series and in series, each of the other average parameters is the corresponding parameter of the compensating optical fiber when weighted by the individual length of the compensating optical fiber. Equal to the arithmetic mean.

かつ、ここで、標準の単一モード回線光ファイバを補償するために、Ｄ_ＤＣＭ＝−１，３６０ｐｓ／ｎｍであり、または、非ゼロの分散シフト単一モード回線光ファイバの例を補償するために、Ｄ_ＤＣＭ＝−６８０ｐｓ／ｎｍである。単一モード回線光ファイバの標準セグメントは、約８０キロメータ（ｋｍ）の長さであり、このことは、標準の単一モード回線光ファイバに対して、−１，３６０ｐｓ／ｎｍの近似累積波長分散、または、非ゼロの分散シフト単一モード回線光ファイバのそのような例に対しては、ほぼ−６８０ｐｓ／ｎｍの近似累積波長分散を与える。−６８０ｐｓ／ｎｍとはわずかに異なる累積分散を有する、非ゼロの分散シフト単一モード回線光ファイバの他の例に対してさえ、Ｄ_ＤＣＭ＝−６８０ｐｓ／ｎｍを使用して品質判定基準を評価することは、完全に有効のままである。さらに、モジュールの品質を評価するために、挿入損失は、モジュールの真の挿入損失ではなく、この損失は、もしモジュールが、累積分散の一部のみを補償するなら比較的低くすることができるが、むしろ、もし累積分散の一部のみを補償することが必要な長さよりわずかに長い補償光ファイバの長さについて、モジュールが累積分散を完全に補償したなら、モジュールが有するであろう挿入損失である。さらに、品質判定基準および非線形性判定基準に対する式において、累積分散は、補償される単一モード回線光ファイバのタイプにより、−１，３６０ｐｓ／ｎｍまたは−６８０ｐｓ／ｎｍとなるように選択されるが、モジュールは、累積分散の他の値を補償するために、または累積分散の一部のみを補償するためにさえ、使用されることもできる。挿入損失は、性能指数が上昇するに従い低減される。挿入損失は、一定の性能指数に対しては一定に留まる。 The module has an insertion loss IL, where

And here to compensate for the example of a non-zero dispersion-shifted single mode line optical fiber, D _DCM = −1,360 ps / nm, to compensate for a standard single mode line optical fiber. D _DCM = −680 ps / nm. The standard segment of a single mode line optical fiber is approximately 80 kilometer (km) long, which is an approximate cumulative chromatic dispersion of -1,360 ps / nm for a standard single mode line optical fiber. Or, for such examples of non-zero dispersion shifted single mode line optical fibers, provides an approximate cumulative chromatic dispersion of approximately -680 ps / nm. Evaluate quality criteria using D _DCM = -680 ps / nm, even for other examples of non-zero dispersion-shifted single mode line optical fibers, with cumulative dispersion slightly different from -680 ps / nm To do remains fully effective. Furthermore, to assess module quality, the insertion loss is not the true insertion loss of the module, but this loss can be relatively low if the module only compensates for some of the cumulative dispersion. Rather, if the module fully compensates the accumulated dispersion for a length of the compensating optical fiber that is slightly longer than needed to compensate for only a portion of the accumulated dispersion, the insertion loss that the module would have is there. Further, in the equations for quality criteria and nonlinearity criteria, the cumulative dispersion is selected to be -1,360 ps / nm or -680 ps / nm, depending on the type of single mode line optical fiber to be compensated. The module can also be used to compensate for other values of the cumulative variance, or even to compensate only for a portion of the cumulative variance. Insertion loss is reduced as the figure of merit increases. Insertion loss remains constant for a fixed figure of merit.

  In order to be able to compensate the chromatic dispersion to dispersion slope ratio of a standard single mode line optical fiber to within about ± 20%, a compensating optical fiber or a series of compensating optical fibers in series is 240 nm to 400 nm. With an average chromatic dispersion to dispersion slope ratio in the range of In order to be able to compensate the ratio of chromatic dispersion to dispersion slope of a standard single mode line optical fiber to within about ± 10%, the compensating optical fiber or series of compensating optical fibers is preferably 270 nm. To a ratio of average chromatic dispersion to dispersion slope in the range of 370 nm.

  In order to be able to compensate for the ratio of chromatic dispersion to dispersion slope of an almost non-zero dispersion-shifted single-mode line optical fiber, the compensating optical fiber or series of compensating optical fibers preferably has an average of less than 200 nm. It has a ratio of chromatic dispersion to dispersion slope.

The module has a non-linearity criterion (NLC) representing the non-linear effect, ie the effect of the non-linear phase, in the specific case of constant loss between the two amplifiers of the two-stage amplifier system, where

However, in other amplification system structures, such as a single stage amplifier system that includes only one amplifier, the non-linearity criteria remains useful anyway. In this nonlinearity criterion, an apparent paradox, that is, increasing the attenuation of an optical fiber with a constant figure of merit leads to a decrease in the nonlinearity criterion and an increase in module performance. Nonlinearity criterion, but even be reduced by reducing the performance index, provided that the condition that the attenuation is increased sufficiently without excessively degrading the effective area and the coefficient n ₂ And

  The module has a quality criterion CQ defined as follows: That is, CQ = IL + 10 log NLC. The two contributions, insertion loss and nonlinearity criterion, are reduced to the same unit and are expressed in dB. The quality criterion CQ represents the overall quality of the compensation module.

  In particular, when integrating the compensation module into a two-stage amplifier system, the quality criterion of the present invention is caused by non-linear effects and the loss represented by the non-linearity criterion is improved proportionally more. Show that it is beneficial to slightly degrade the insertion loss. For example, if increasing the insertion loss by 1 dB reduces the contribution of the nonlinearity criterion to the quality criterion to 2 dB, this increase is beneficial. Since the insertion loss between the two amplifiers of the two-stage amplification system is fixed, only the benefit of any reduction of the insertion loss below the fixed threshold results in a reduction of the non-linear effect, which reduction of the insertion loss. It can be obtained more easily by a significant reduction in quality criteria with a slight increase. Indeed, below the fixed threshold, no further reduction in insertion loss will lead to any improvement in the overall optical loss balance. This is because the optical loss balance is canceled by a corresponding increase in the attenuation of the attenuator. The only advantage associated with this reduction in insertion loss is obtained with respect to the ability to resist non-linear effects, which replaces a slight increase in insertion loss for a corresponding greater reduction in non-linearity criteria. It can be improved more effectively and more easily.

Using a selected constant figure of merit of the compensating optical fiber, reducing the quality criterion is equivalent to reducing the nonlinearity criterion. Because the insertion loss is constant at a constant figure of merit for the compensating optical fiber, where each variable that changes is a parameter of the compensating optical fiber. Reducing the non-linearity criterion in certain performance index is equivalent to increasing the product of the multiplication by the effective area, and is divided by a factor n ₂ decay. reducing the n _2, and increasing the effective area is that the look quite natural, to increase the attenuation of the compensation optical fiber, looks somewhat paradoxical.

  FIG. 1 is a diagram showing an example of a transmission line integrated with a compensation module of the present invention. A transmission line corresponds to the segments that make up the communication system when it is periodically repeated and combined with a transmitting and receiving device. The transmission line continuously includes the line optical fiber 1 and the amplification and compensation system 6 in the propagation direction of the optical signal. The amplification and compensation system 6 includes an upstream amplifier 2, an attenuator 3, a compensation module 4 of the present invention, and a downstream amplifier 5 in series. Downstream from the downstream amplifier 5 is the line optical fiber 1 of the next segment. After propagating along the line optical fiber 1, the optical signal is amplified by the upstream amplifier 2 and attenuated by the attenuator 3 before entering the next segment, that is, the next transmission line, and the wavelength dispersion of the optical signal. Is compensated by the compensation module 4 and amplified again by the downstream amplifier 5. In different embodiments, the attenuator 3 and the amplifier 5 are omitted.

FIG. 2 is a diagram showing an example of the compensation module of the present invention. The compensation module 4 includes an enclosure 49 that includes an input terminal 41, an upstream mode converter 46, a chromatic dispersion compensating optical line 40, a downstream mode converter 47, and an output terminal 42 in series. The compensation optical line 40 can include one or a plurality of optical fibers in series interconnected by connectors. The upstream mode converter 46 converts most of the light energy propagating in the LP ₀₁ fundamental mode to a higher order mode, eg, LP ₀₂ . Downstream mode converter 47, most of the light energy propagating in the higher order mode _{LP 02,} and converts the fundamental mode _{LP 01.} In FIG. 2, for example, the compensating optical line 40 includes two compensating optical fibers 43 and 45 connected together by a connector 44. On the upstream side, at the output of the attenuator 3, an optical signal enters through the input terminal 41, is converted from the fundamental mode to the higher order mode by the upstream converter 46, propagates in the compensating optical fiber 43, and is connected to the connector. 44, propagates through the compensating optical fiber 45, is converted from the higher order mode to the fundamental mode, and exits via the downstream output terminal 42, that is, at the input of the downstream amplifier 5.

FIG. 3 is a table comparing the relative performance of a prior art compensation module and an example of a compensation module according to the present invention when compensating a standard single mode line optical fiber. The first column gives the number of example compensation modules. Examples of prior art compensation modules are numbered B1, B2, B3. Examples B1, B2, and B3 correspond to a module that couples two compensating optical fibers in series, one of the two fibers being a HOM multimode fiber and the other of the two fibers being a single mode fiber. Yes, all optical fiber characteristics shown in the table correspond to the characteristics of the HOM multimode compensating optical fiber. Examples of compensation modules of the present invention are numbered A1, A2, A3, A4. The next column gives the cumulative chromatic dispersion negative of the line optical fiber, which is the negative of chromatic dispersion that must be compensated to fully compensate the 80 km line optical fiber, which is D _DCM . And is expressed in ps / nm. The next column gives the chromatic dispersion of the compensating optical fiber, which is indicated by D _DCF and expressed in ps / nm · km. The next column gives the dispersion slope of the compensating optical fiber, which is denoted _SDDCF and is expressed in ps / nm ² · km. The next column gives the ratio of the average chromatic dispersion to the dispersion slope of the compensating optical fiber, which is expressed as D _DCF / S _DCF and expressed in nm. The next column gives the attenuation coefficient of the compensating optical fiber, which is denoted α _DCF and expressed in dB / km. The next column gives the figure of merit of the compensating optical fiber, which is indicated by FOM _DCF and expressed in ps / nm · dB. The next three columns are the input loss at the input terminal of the compensation module, if any (for the second type of prior art module where the output converter is actually installed between the two compensation optical fibers) , The connection loss at the junction between the HOM multimode compensating optical fiber and the single mode compensating optical fiber, and the output loss at the output terminal of the compensation module, respectively, which are respectively Γ _in , Γ _inter , and It is indicated by Γ _out and expressed in dB. The next column gives the insertion loss of the compensation module, which is denoted IL and expressed in dB. The next column gives the effective area of the compensating optical fiber, which is denoted A _eff and is expressed in μm ² . The next column gives the average second order coefficient of the refractive index of the compensating optical fiber as a function of the intensity of the optical signal propagating in the compensating optical fiber, which is denoted n ₂ and is 10 ⁻²⁰ m ^2. It is represented by / W. The next column gives the compensation module nonlinearity criterion, which is expressed in NLC and expressed in 10 ⁻⁶ km / W · dB. The next column gives the quality criteria for the compensation module, which is indicated in CQ and expressed in dB.

  The compensation module according to the first aspect of the invention does not use a single mode compensating optical fiber in the compensation module, and is lower and therefore better than the prior art module for equivalent quality criteria. There are also no quality criteria, and the compensation module uses optical fibers that have a much lower figure of merit and therefore are much less costly to produce.

  Example A1 is excluded from the first aspect of the invention. This is because the quality criterion is too high and is therefore insufficient.

  The compensation module of the present invention preferably has a very good quality criterion. To this end, the compensating optical fiber or series of compensating optical fibers has an average chromatic dispersion that is sufficiently negative for a quality criterion that is less than 9 dB.

  The compensation module of the present invention preferably has excellent quality criteria. To this end, the compensating optical fiber or series of compensating optical fibers has an average chromatic dispersion that is sufficiently negative for a quality criterion that is less than 8.5 dB.

  The insertion loss is preferably less than 5 dB, which is very beneficial in certain cases of amplification and compensation systems using only one amplifier.

  In order to facilitate the improvement of the quality criterion, at least one of the compensating optical fibers in the compensating optical line preferably has a core with at least four core segments, to which a core cladding is added. .

  In order to achieve a good linearity depending on the wavelength of the mean chromatic dispersion to dispersion slope ratio, while at least one of the compensating optical fibers in the compensating optical line allows at least 5 A core having a core segment is provided, and a core cladding is added to the core.

FIG. 4 is a table comparing the relative performance of a prior art compensation module and an example of a compensation module according to the present invention when compensating a non-zero dispersion shifted single mode line optical fiber. The first column gives the number of example compensation modules. Prior art compensation module examples are numbered B1, B2, C1, C2, C3. Examples of compensation modules according to the invention are numbered A5, A6, A7. Examples B1 and B2 correspond to a module that couples two compensating optical fibers in series, one of these fibers being a HOM multimode fiber and the other of these fibers being a single mode fiber; All the optical fiber characteristics shown in the table correspond to the characteristics of the HOM multimode compensating optical fiber. The next column gives the cumulative chromatic dispersion negative of the line optical fiber, which is the negative of chromatic dispersion that must be compensated to fully compensate the 80 km line optical fiber, which is D _DCM . And is expressed in ps / nm. The cumulative chromatic dispersion of a non-zero dispersion shifted single mode line optical fiber is lower than that of a standard single mode line optical fiber. This is because the non-zero dispersion shifted single mode line optical fiber has lower chromatic dispersion. The next column gives the chromatic dispersion of the compensating optical fiber, which is indicated by D _DCF and expressed in ps / nm · km. The next column gives the dispersion slope of the compensating optical fiber, which is denoted _SDDCF and is expressed in ps / nm ² · km. The next column gives the ratio of the average chromatic dispersion to the dispersion slope of the compensating optical fiber, which is expressed as D _DCF / S _DCF and expressed in nm. The next column gives the attenuation coefficient of the compensating optical fiber, which is denoted α _DCF and expressed in dB / km. The next column gives the figure of merit of the compensating optical fiber, which is indicated by FOM _DCF and expressed in ps / nm · dB. The next three columns are the input loss at the input terminal of the compensation module (for the second type of prior art module where the output converter is actually installed between the two compensation optical fibers). For example, the connection loss at the junction between the HOM multimode compensating optical fiber and the single mode compensating optical fiber and the output loss at the output terminal of the compensation module are respectively given by Γ _in , Γ _inter , And Γ _out and expressed in dB. The next column gives the insertion loss of the compensation module, which is denoted IL and expressed in dB. The next column gives the effective area of the compensating optical fiber, which is denoted A _eff and is expressed in μm ² . The next column gives the mean second order coefficient of the refractive index of the compensating optical fiber as a function of the intensity of the optical signal propagating in the fiber, which is denoted n ₂ and is 10 ⁻²⁰ m ² / W. expressed. The next column gives the compensation module nonlinearity criterion, which is expressed in NLC and expressed in 10 ⁻⁶ km / W · dB. The next column gives the quality criteria for the compensation module, which is indicated in CQ and expressed in dB.

  The compensation module of the present invention has a quality criterion that is much lower than the prior art modules and therefore much better. There is a difference of about 1 dB between the worst compensation module obtained by the method of the present invention and the best compensation module obtained in the prior art. The improvement of 1 dB is already a considerable improvement.

  The present invention preferably relates to a compensation module having a very good quality criterion. For this reason, the compensating optical fiber or series of compensating optical fibers has an average chromatic dispersion that is sufficiently negative for a quality criterion that is less than 5 dB.

  The present invention preferably relates to a compensation module having excellent quality criteria. To this end, the compensating optical fiber or series of compensating optical fibers has an average chromatic dispersion that is sufficiently negative for a quality criterion that is less than 4.5 dB.

  The insertion loss is preferably less than 4 dB, which is very useful in certain cases of amplification and compensation systems that use only one amplifier.

  In order to achieve a good linearity depending on the wavelength of the ratio of the average chromatic dispersion to the dispersion slope, while at least one of the compensating optical fibers in the compensating optical line is at least four Having a core with a core segment, to which a core cladding is added.

  This is the difference compared to the compensation module for a standard single mode line optical fiber, which requires at least 5 core segments under the same conditions. This is because the ratio of chromatic dispersion to dispersion slope of a standard single-mode line optical fiber is generally higher than the ratio of chromatic dispersion to dispersion slope of a non-zero dispersion shifted line optical fiber.

  Enables improved quality criteria while achieving good linearity depending on the wavelength of the chromatic dispersion to dispersion slope ratio when the ratio of average chromatic dispersion to dispersion slope is very large, eg, exceeding 200 nm To do so, at least one of the compensating optical fibers in the compensating optical line has a core with at least five core segments, to which a core cladding is added.

FIG. 5 is a curve plotting the change in quality criteria as a function of the performance index of the compensating optical fiber at a selected constant chromatic dispersion for the compensating optical fiber and when compensating a standard single mode line optical fiber. It is a figure which shows a group. The general trend of the curves shown in FIG. 5 applies equally to compensation for non-zero dispersion shifted line optical fibers. The quality criterion CQ expressed in dB is plotted on the vertical axis. The figure of merit FOM _DCF expressed in ps / nm · dB is plotted along the horizontal axis. The curve CA corresponds to chromatic dispersion of −300 ps / nm · km. Curve CB corresponds to chromatic dispersion of −350 ps / nm · km. Curve CC corresponds to chromatic dispersion of −400 ps / nm · km. Due to its relatively shallow slope and its relatively wide spacing, the curves CA, CB, CC increase the figure of merit of the compensating optical fiber at constant chromatic dispersion in order to reduce and thus improve the quality criterion. This shows that it is more effective to reduce the chromatic dispersion of the compensating optical fiber at a certain figure of merit than This is even more true if the figure of merit is large and especially greater than about 300 ps / nm · dB.

  In order to obtain a simpler compensation module, the compensation optical line preferably comprises a single optical fiber connecting the input terminal to the output terminal. Multiple compensating optical fibers in series provide better compensation for the dispersion slope of the line optical fiber at the expense of some complexity.

  The signal amplification and chromatic dispersion compensation system preferably includes a first signal amplifier, a signal attenuator, a chromatic dispersion compensation module of the present invention, and a second signal amplifier in series.

  In another preferred embodiment, the signal amplification and chromatic dispersion compensation system includes a single signal amplifier followed by the chromatic dispersion compensation module of the present invention.

  A very good high quality criterion for the compensation module of the present invention which is better than the quality criterion of the prior art and much better than the quality criterion of the compensation module based only on single mode compensating optical fiber Because of this, it is possible to use a compensation module with only one amplifier.

  The transmission line preferably comprises in succession a single mode line optical fiber for transmitting information in the used spectral range and the signal amplification and chromatic dispersion compensation system of the present invention.

  FIG. 6 is a table of absolute maximum index difference and radius values for several examples of HOM multimode compensating optical fiber profiles used in the compensation module of the present invention. The left hand side column identifies profiles A1 through A7. The numbers A1 to A7 are the same as those in FIGS. Two numbers that are the same correspond to the same compensating optical fiber. The second column shows the number of core segments in the related example core index profile. The next six columns give the radius in μm of the various core index profiles. The last six columns give 1000 times the difference in refractive index relative to the constant refractive index of the cladding (no unit). Not all profiles are filled in because not all profiles have the same number of core segments. A negative index difference indicates an embedded core segment.

FIG. 7 is a table of other characteristics of the HOM multimode compensating optical fiber profile shown in FIG. The columns in this table that do not include numbers, but include only dashes, correspond to characteristics that are so bad as to render the optical fiber unusable at the relevant wavelength or the relevant operating spectral range. The column on the left hand side identifies a profile as already described above. The next column gives the number of core segments in each profile. For each profile, the other columns give the fiber characteristics corresponding to the associated profile. The next column gives the effective area A _eff expressed in μm ² at a wavelength of 1,550 nm. The next column gives the chromatic dispersion expressed in ps / nm · km at a wavelength of 1,550 nm. The next seven columns show the dispersion expressed in ps / nm ² · km at wavelengths of 1,530 nm, 1,550 nm, 1,565 nm, 1,570 nm, 1,580 nm, 1,590 nm, and 1,605 nm, respectively. Giving a gradient. The next column gives the lowest chromatic dispersion wavelength expressed in nm. The last three columns represent the maximum expressed as a percentage of the operating spectral range in the range 1,530 nm to 1,565 nm, 1,530 nm to 1,580 nm, and 1,530 nm to 1,605 nm, respectively. A relative gradient change is given. The relative change in the dispersion slope over the operating spectral range is the quotient obtained by dividing the difference between the maximum dispersion slope over the operating spectral range and the minimum dispersion slope over the operating spectral range by the average dispersion slope over the operating spectral range. It corresponds to. Insufficient results in the last column correspond to a maximum relative change in gradient that is much larger than the maximum relative change in the other columns, and can be explained in particular by the minimum chromatic dispersion wavelength that is too close to the upper end of the relevant operating spectral range .

  Examples A2 and A6 are excluded from the second aspect of the invention. This is because the linearity of the dispersion gradient according to the wavelength is relatively insufficient, as is the linearity of the ratio of the chromatic dispersion to the dispersion gradient. These examples have only three core segments.

  Example A1 is excluded from the second aspect of the invention. This is because negative chromatic dispersion is not sufficiently negative. This example has only four core segments.

  Having less than 4 core segments, in fact, makes it impossible to match very low negative chromatic dispersion to a very large chromatic dispersion to dispersion slope ratio with very good linearity as a function of wavelength. Looks like.

  Having three or fewer core segments, in fact, makes it impossible to match very low negative chromatic dispersion to a large chromatic dispersion to dispersion slope ratio with very good linearity as a function of wavelength. .

  FIG. 8 is a diagram showing an example of a core profile including four core segments of a HOM multimode compensating optical fiber used in the compensation module of the present invention. The radius expressed in μm is plotted along the horizontal axis. 1,000 times the refractive index difference is plotted on the vertical axis (no unit). The first core segment, also known as the central core segment, has a maximum refractive index difference Δn1 for a constant refractive index of the cladding and an outer radius r1. The maximum refractive index difference Δn1 is positive. The refractive index is preferably constant between the radius of zero and the radius r1. The second core segment, also known as the first peripheral core segment, has an absolute maximum refractive index difference value Δn2 for a constant refractive index of the cladding and an outer radius r2. The absolute maximum refractive index difference value Δn2 can be either positive or negative. The refractive index is preferably constant between radius r1 and radius r2. The third core segment, also known as the second peripheral core segment, has an absolute maximum refractive index difference value Δn3 for a constant refractive index of the cladding and an outer radius r3. The absolute maximum refractive index difference value Δn3 can be either positive or negative. The refractive index is preferably constant between radius r2 and radius r3. The fourth core segment, also known as the third peripheral core segment, has an absolute maximum refractive index difference value Δn4 for a constant refractive index of the cladding and an outer radius r4. The absolute maximum refractive index difference value Δn4 can be either positive or negative. The refractive index is preferably constant between radius r3 and radius r4. Beyond the radius r4, the cladding has a constant refractive index.

  FIG. 9 is a diagram schematically illustrating an example of a core profile including five core segments of a HOM multimode compensating optical fiber used in the compensation module of the present invention. The radius expressed in μm is plotted along the horizontal axis. 1,000 times the refractive index difference is plotted on the vertical axis (no unit). The first core segment, also known as the central core segment, has an absolute maximum refractive index difference value Δn1 for a constant refractive index of the cladding and an outer radius r1. The maximum refractive index difference Δn1 is positive. The refractive index is preferably constant between the radius of zero and the radius r1. The second core segment, also known as the first peripheral core segment, has an absolute maximum refractive index difference value Δn2 and an external radius r2 for a constant refractive index of the cladding. The absolute maximum refractive index difference value Δn2 can be either positive or negative. The refractive index is preferably constant between radius r1 and radius r2. The third core segment, also known as the second peripheral core segment, has an absolute maximum refractive index difference value Δn3 for a constant refractive index of the cladding and an outer radius r3. The absolute maximum refractive index difference value Δn3 can be either positive or negative. The refractive index is preferably constant between radius r2 and radius r3. The fourth core segment, also known as the third peripheral core segment, has an absolute maximum refractive index difference value Δn4 for a constant refractive index of the cladding and an outer radius r4. The absolute maximum refractive index difference value Δn4 can be either positive or negative. The refractive index is preferably constant between radius r3 and radius r4. The fifth core segment, also known as the fourth peripheral core segment, has an absolute maximum refractive index difference value Δn5 for a constant refractive index of the cladding and an outer radius r5. The absolute maximum refractive index difference value Δn5 can be positive or negative. The refractive index is preferably constant between radius r4 and radius r5. Beyond the radius r5, the cladding has a constant refractive index.

It is a figure which shows the example of the transmission line which integrated the compensation module of this invention. It is a figure which shows the example of the compensation module of this invention. FIG. 5 is a table comparing the relative performance of a prior art compensation module and an example of a compensation module of the present invention when compensating a standard single mode line optical fiber. 6 is a table comparing the relative performance of a prior art compensation module and an example of a compensation module of the present invention when compensating a non-zero dispersion shifted single mode line optical fiber. FIG. 6 is a diagram showing a group of curves plotting a change in quality criterion according to a figure of merit of a compensating optical fiber at a fixed constant chromatic dispersion selected for the compensating optical fiber when compensating a standard single mode line optical fiber. is there. 6 is a table showing absolute radius and maximum index difference values for several examples of HOM multimode compensating optical fiber profiles used in the compensation module of the present invention. 7 is a table showing other characteristics of the profile of the HOM multimode compensating optical fiber shown in FIG. 6. FIG. 6 shows an example of a core profile with four core segments of a HOM multimode compensating optical fiber used in the compensation module of the present invention. FIG. 6 shows an example of a core profile with five core segments of a HOM multimode compensating optical fiber used in the compensation module of the present invention.

Claims (28)

A chromatic dispersion compensation module,
An enclosure (49) including an input terminal (41) and an output terminal (42);
A higher-order mode chromatic dispersion compensating optical line (40) installed inside the enclosure and disposed between the input terminal and the output terminal, the higher-order mode chromatic dispersion compensating optical line (40), One or a plurality of HOM multimode chromatic dispersion compensating optical fibers (43, 45) in series and without any single mode optical fiber;
The chromatic dispersion compensation module further includes:
An input mode converter (46) installed between an input terminal and a higher-order mode chromatic dispersion compensating optical line for converting a fundamental mode into the higher-order mode;
An output mode converter (47) installed between the higher-order mode chromatic dispersion compensating optical line and the output terminal, for converting the higher-order mode into a fundamental mode;
A chromatic dispersion compensation module is configured to be inserted using a input terminal and an output terminal into a transmission line including a standard single-mode line optical fiber configured to transmit information in the use spectrum region;
The input terminal and the input mode converter both introduce an input loss Γ _in expressed in dB into the transmission line;
An output terminal and an output mode converter both introduce an output loss Γ _out expressed in dB into the transmission line;
If an additional connection exists between multimode chromatic dispersion compensating optical fibers, a connection loss Γ _inter expressed in dB is introduced into the transmission line together,
A set of multimode chromatic dispersion compensating optical fibers or series multimode chromatic dispersion compensating optical fibers is represented by an average attenuation coefficient α _DCF expressed in dB / km and ps / nm · km at a wavelength of 1,550 nm. Average chromatic dispersion D _DCF , expressed as ps / nm ^{2 ·} km, and negative, and negative chromatic dispersion S _DCF , ratio of average chromatic dispersion to dispersion slope expressed as nm D _DCF / S _{DCF Expressed} as an average figure of merit FOM _DCF defined as -D _DCF / α _DCF expressed in ps / nm · dB, an average effective area A _eff expressed in μm ² , and 10 ⁻²⁰ m ² / W Presents a plurality of average parameters, including an average second order coefficient n ₂ of refractive index as a function of intensity,
The ratio of average chromatic dispersion to dispersion slope is the ratio between average chromatic dispersion and average dispersion slope;
The average figure of merit is the negative of the ratio between the average chromatic dispersion and the average attenuation coefficient;
In the case of a single multimode chromatic dispersion compensating optical fiber, the average attenuation coefficient is treated together with the corresponding attenuation coefficient of the single multimode chromatic dispersion compensating optical fiber, and the multimode in series In the case of a set of chromatic dispersion compensating optical fibers, the average attenuation coefficient is the sum of the individual contributions of the various multimode chromatic dispersion compensating optical fibers to the total length of the series of multimode chromatic dispersion compensating optical fibers. Equal to the sum of the corresponding attenuation factors of various multimode chromatic dispersion compensating optical fibers, weighted by the ratio of splice loss divided by length,
In the case of a single multimode chromatic dispersion compensating optical fiber, each of the other average parameters is treated together with a corresponding parameter of the single multimode chromatic dispersion compensating optical fiber, and in series In the case of a multimode chromatic dispersion compensating optical fiber set, each of the other average parameters is weighted by an individual length of the various multimode chromatic dispersion compensating optical fibers. Is the arithmetic mean of the corresponding parameters of the chromatic dispersion compensating optical fiber,
The chromatic dispersion compensation module has an insertion loss IL expressed in dB, where

And where D _DCM = -1,360 ps / nm,
The chromatic dispersion compensation module has a nonlinearity criterion NLC that represents the effect of nonlinear phase and is represented by 10 ⁻⁶ km / W · dB, where

And
The chromatic dispersion compensation module exhibits a quality criterion CQ expressed in dB, where
CQ = IL + 10log NLC
And
A set of multimode chromatic dispersion compensating optical fibers or series multimode chromatic dispersion compensating optical fibers
First, it has a negative average chromatic dispersion lower than −200 ps / nm · km,
Second, having a ratio of average chromatic dispersion to dispersion slope ranging from 240 nm to 400 nm, and
Third, a module having an average chromatic dispersion that is sufficiently negative with respect to a quality criterion that is less than 9.5 dB.   A multimode chromatic dispersion compensating optical fiber or a set of serial multimode chromatic dispersion compensating optical fibers has an average chromatic dispersion that is sufficiently negative with respect to a quality criterion that is less than 9 dB. Item 2. The module according to item 1.   A set of multimode chromatic dispersion compensating optical fibers or series multimode chromatic dispersion compensating optical fibers has an average chromatic dispersion that is sufficiently negative for a quality criterion that is less than 8.5 dB The module according to claim 1.   The module according to claim 1, wherein the insertion loss is less than 5 dB.   At least one of the multi-mode chromatic dispersion compensating optical fibers of the higher-order mode chromatic dispersion compensating optical line has a core having at least four core segments, and a core clad is added to the core. The module according to claim 5.   At least one of the multimode chromatic dispersion compensating optical fibers of the higher-order mode chromatic dispersion compensating optical line has a core having at least five core segments, and a core clad is added to the core. The module according to claim 1.   6. A multimode chromatic dispersion compensating optical fiber or a set of multimode chromatic dispersion compensating optical fibers in series has an average chromatic dispersion to dispersion slope ratio in the range of 270 nm to 370 nm. Module described in. A chromatic dispersion compensation module,
An enclosure (49) including an input terminal (41) and an output terminal (42);
A higher-order mode chromatic dispersion compensating optical line (40) installed inside the enclosure and disposed between the input terminal and the output terminal, the higher-order mode chromatic dispersion compensating optical line (40), One or a plurality of HOM multimode chromatic dispersion compensating optical fibers (43, 45) in series and without any single mode optical fiber;
The chromatic dispersion compensation module further includes:
An input mode converter (46) installed between an input terminal and a higher-order mode chromatic dispersion compensating optical line for converting a fundamental mode into the higher-order mode;
An output mode converter (47) installed between the higher-order mode chromatic dispersion compensating optical line and the output terminal, for converting the higher-order mode into a fundamental mode;
The chromatic dispersion compensation module is configured to be inserted into a transmission line including a standard single-mode line optical fiber configured to transmit information in a spectral region of use using an input terminal and an output terminal. And
At least one of a multimode chromatic dispersion compensating optical fiber or a serial multimode chromatic dispersion compensating optical fiber has a core having at least five core segments, and a core cladding is added to the core, and at least five cores are added. The multi-mode chromatic dispersion compensating optical fiber having a core with a segment simultaneously has a negative chromatic dispersion lower than −300 ps / nm · km at a wavelength of 1,550 nm, and a chromatic dispersion versus dispersion slope larger than 200 nm. A module having a ratio of A chromatic dispersion compensation module,
An enclosure (49) including an input terminal (41) and an output terminal (42);
A higher-order mode chromatic dispersion compensating optical line (40) installed inside the enclosure and disposed between the input terminal and the output terminal, the higher-order mode chromatic dispersion compensating optical line (40), One or a plurality of HOM multimode chromatic dispersion compensating optical fibers (43, 45) in series and without any single mode optical fiber;
The chromatic dispersion compensation module further includes:
An input mode converter (46) installed between an input terminal and a higher-order mode chromatic dispersion compensating optical line for converting a fundamental mode into the higher-order mode;
An output mode converter (47) installed between the higher-order mode chromatic dispersion compensating optical line and the output terminal, for converting the higher-order mode into a fundamental mode;
A chromatic dispersion compensation module uses an input terminal and an output terminal for a transmission line including a single mode non-zero (at 1,550 nm) dispersion shifted line optical fiber configured to transmit information in the spectral region of use. Configured to be inserted,
The input terminal and the input mode converter both introduce an input loss Γ _in expressed in dB into the transmission line;
An output terminal and an output mode converter both introduce an output loss Γ _out expressed in dB into the transmission line;
If an additional connection exists between multimode chromatic dispersion compensating optical fibers, a connection loss Γ _inter expressed in dB is introduced into the transmission line together,
A set of multimode chromatic dispersion compensating optical fibers or series multimode chromatic dispersion compensating optical fibers is represented by an average attenuation coefficient α _DCF expressed in dB / km and ps / nm · km at a wavelength of 1,550 nm. Average chromatic dispersion D _DCF , expressed as ps / nm ² · km, and negative, and negative chromatic dispersion S _DCF , ratio of average chromatic dispersion to dispersion slope expressed as nm D _DCF / S _{DCF Expressed} as an average figure of merit FOM _DCF defined as -D _DCF / α _DCF expressed in ps / nm · dB, an average effective area A _eff expressed in μm ² , and 10 ⁻²⁰ m ² / W Presents a plurality of average parameters, including an average second order coefficient n ₂ of refractive index as a function of intensity,
The ratio of average chromatic dispersion to dispersion slope is the ratio between average chromatic dispersion and average dispersion slope;
The average figure of merit is the negative of the ratio between the average chromatic dispersion and the average attenuation coefficient;
In the case of a single multimode chromatic dispersion compensating optical fiber, the average attenuation coefficient is treated together with the corresponding attenuation coefficient of the single multimode chromatic dispersion compensating optical fiber, and the multimode in series In the case of a set of chromatic dispersion compensating optical fibers, the average attenuation coefficient is the sum of the individual contributions of the various multimode chromatic dispersion compensating optical fibers to the total length of the series of multimode chromatic dispersion compensating optical fibers. Equal to the sum of the corresponding attenuation factors of various multimode chromatic dispersion compensating optical fibers, weighted by the ratio of splice loss divided by length,
In the case of a single multimode chromatic dispersion compensating optical fiber, each of the other average parameters is treated together with a corresponding parameter of the single multimode chromatic dispersion compensating optical fiber, and in series In the case of a multimode chromatic dispersion compensating optical fiber set, each of the other average parameters is weighted by an individual length of the various multimode chromatic dispersion compensating optical fibers. Is the arithmetic mean of the corresponding parameters of the chromatic dispersion compensating optical fiber,
The chromatic dispersion compensation module has an insertion loss IL expressed in dB, where

And where D _DCM = −680 ps / nm,
The chromatic dispersion compensation module has a nonlinearity criterion NLC that represents the effect of nonlinear phase and is represented by 10 ⁻⁶ km / W · dB, where

And
The chromatic dispersion compensation module has a quality criterion CQ expressed in dB, where
CQ = IL + 10log NLC
And
A set of multimode chromatic dispersion compensating optical fibers or series multimode chromatic dispersion compensating optical fibers
First, it exhibits a negative average chromatic dispersion lower than −250 ps / nm · km,
Second, a module that exhibits a sufficiently negative average chromatic dispersion relative to a quality criterion that is less than 5 dB.   A multimode chromatic dispersion compensating optical fiber or a set of serial multimode chromatic dispersion compensating optical fibers have an average chromatic dispersion that is sufficiently negative for a quality criterion that is less than 5 dB. Item 10. The module according to Item 9.   A set of multimode chromatic dispersion compensating optical fibers or series multimode chromatic dispersion compensating optical fibers has an average chromatic dispersion that is sufficiently negative for a quality criterion that is less than 4.5 dB. The module according to claim 10.   12. Module according to claim 11, characterized in that the insertion loss is less than 4 dB.   At least one of the multi-mode chromatic dispersion compensating optical fibers of the higher-order mode chromatic dispersion compensating optical line has a core having at least four core segments, and a core clad is added to the core. The module according to claim 9.   At least one of the multimode chromatic dispersion compensating optical fibers of the higher-order mode chromatic dispersion compensating optical line has a core having at least five core segments, and a core clad is added to the core; The module according to claim 13.   14. A multimode chromatic dispersion compensating optical fiber or a set of serial multimode chromatic dispersion compensating optical fibers has an average chromatic dispersion to dispersion slope ratio of less than 200 nm, according to claim 9 or 13. module. A chromatic dispersion compensation module,
An enclosure (49) including an input terminal (41) and an output terminal (42);
A higher-order mode chromatic dispersion compensating optical line (40) installed inside the enclosure and disposed between the input terminal and the output terminal, the higher-order mode chromatic dispersion compensating optical line (40), One or a plurality of HOM multimode chromatic dispersion compensating optical fibers (43, 45) in series and without any single mode optical fiber;
The chromatic dispersion compensation module further includes:
An input mode converter (46) installed between an input terminal and a higher-order mode chromatic dispersion compensating optical line for converting a fundamental mode into the higher-order mode;
An output mode converter (47) installed between the higher-order mode chromatic dispersion compensating optical line and the output terminal, for converting the higher-order mode into a fundamental mode;
A chromatic dispersion compensation module uses an input terminal and an output terminal for a transmission line including a single mode non-zero (at 1,550 nm) dispersion shifted line optical fiber configured to transmit information in the spectral region of use. Configured to be inserted, and
At least one of a multimode chromatic dispersion compensating optical fiber or a serial multimode chromatic dispersion compensating optical fiber has a core having at least four core segments, and a cladding is added to the core, and at least four cores are provided. The multi-mode chromatic dispersion compensating optical fiber having a core with a segment has a negative chromatic dispersion lower than −300 ps / nm · km at a wavelength of 1,550 nm, and a chromatic dispersion versus dispersion slope larger than 80 nm. A module having a ratio of   10. The module according to claim 1, wherein the higher-order mode chromatic dispersion compensating optical line is composed of a single optical fiber connecting the input mode converter to the output mode converter. .   The higher-order mode chromatic dispersion compensating optical line includes a plurality of optical fibers of the same group, that is, a plurality of segments of the same optical fiber, or a plurality of optical fibers that are similar within an assembly tolerance. The module according to claim 1, 8 or 9.   The high-order mode chromatic dispersion compensating optical line includes a plurality of separated optical fibers, and the used spectral region includes at least two of spectral bands S, C, and L. Item 18. The module according to Item 1 or 8 or 9 or 16.   Signal amplification and chromatic dispersion comprising a first signal amplifier (2), a signal attenuator (3), a chromatic dispersion compensation module (4) according to claim 1, and a second signal amplifier (5) in succession. Compensation system.   Signal amplification and chromatic dispersion compensation system comprising a single signal amplifier (2) followed by a chromatic dispersion compensation module (4) according to claim 1.   Transmission line comprising a single-mode line optical fiber (1) configured to transmit information in the use spectrum region and a signal amplification and chromatic dispersion compensation system (6) according to claim 20 or 21 in series. A method for configuring a chromatic dispersion compensation module, comprising:
The chromatic dispersion compensation module is
An enclosure including input and output terminals;
A high-order mode chromatic dispersion compensating optical line that is installed inside the enclosure and disposed between the input terminal and the output terminal. Or a plurality of HOM multimode chromatic dispersion compensating optical fibers in series and no single mode optical fiber,
The chromatic dispersion compensation module further includes:
An input mode converter installed between an input terminal and a higher-order mode chromatic dispersion compensating optical line, for converting a fundamental mode into the higher-order mode;
A high-order mode chromatic dispersion compensating optical line and an output terminal, and configured to include an output mode converter for converting the high-order mode into a fundamental mode;
The chromatic dispersion compensation module is configured to be inserted into a transmission line including a single-mode line optical fiber configured to transmit information in a use spectrum region, using an input terminal and an output terminal;
The input terminal and the input mode converter both introduce an input loss Γ _in expressed in dB into the transmission line;
An output terminal and an output mode converter both introduce an output loss Γ _out expressed in dB into the transmission line;
If an additional connection exists between multimode chromatic dispersion compensating optical fibers, a connection loss Γ _inter expressed in dB is introduced into the transmission line together,
A set of multimode chromatic dispersion compensating optical fibers or series multimode chromatic dispersion compensating optical fibers is represented by an average attenuation coefficient α _DCF expressed in dB / km and ps / nm · km at a wavelength of 1,550 nm. Average chromatic dispersion D _DCF , expressed as ps / nm ² · km, and negative, and negative chromatic dispersion S _DCF , ratio of average chromatic dispersion to dispersion slope expressed as nm D _DCF / S _{DCF Expressed} as an average figure of merit FOM _DCF defined as -D _DCF / α _DCF expressed in ps / nm · dB, an average effective area A _eff expressed in μm ² , and 10 ⁻²⁰ m ² / W Presents a plurality of average parameters, including an average second order coefficient n ₂ of refractive index as a function of intensity,
The ratio of average chromatic dispersion to dispersion slope is the ratio between average chromatic dispersion and average dispersion slope;
The average figure of merit is the negative of the ratio between the average chromatic dispersion and the average attenuation coefficient;
In the case of a single multimode chromatic dispersion compensating optical fiber, the average attenuation coefficient is treated together with the corresponding attenuation coefficient of the single multimode chromatic dispersion compensating optical fiber, and the multimode in series In the case of a set of chromatic dispersion compensating optical fibers, the average attenuation coefficient is the sum of the individual contributions of the various multimode chromatic dispersion compensating optical fibers to the total length of the series of multimode chromatic dispersion compensating optical fibers. Equal to the sum of the corresponding attenuation factors of various multimode chromatic dispersion compensating optical fibers, weighted by the ratio of splice loss divided by length,
In the case of a single multimode chromatic dispersion compensating optical fiber, each of the other average parameters is treated together with a corresponding parameter of the single multimode chromatic dispersion compensating optical fiber, and in series In the case of a multimode chromatic dispersion compensating optical fiber set, each of the other average parameters is weighted by an individual length of the various multimode chromatic dispersion compensating optical fibers. Is the arithmetic mean of the corresponding parameters of the chromatic dispersion compensating optical fiber,
The chromatic dispersion compensation module is configured to exhibit an insertion loss IL expressed in dB, where

In addition, here, the _DCMM exhibits a negative cumulative dispersion of the line optical fiber, the chromatic dispersion compensation module exhibits a nonlinear phase effect, and the nonlinearity determination expressed by 10 ⁻⁶ km / W · dB. Configured to have a reference NLC, where:

And
The chromatic dispersion compensation module is configured to exhibit a quality criterion CQ expressed in dB, where
CQ = IL + 10log NLC
And
The configuration method includes an optimization step for optimizing the chromatic dispersion compensation module, and the optimization step is to reduce a quality criterion.   A high-order mode chromatic dispersion compensating optical fiber having a core having at least four core segments, to which a core cladding is added, and at a wavelength of 1,550 nm, simultaneously, -300 ps / nm A higher order mode chromatic dispersion compensating optical fiber having a negative chromatic dispersion below km and a ratio of chromatic dispersion to dispersion slope greater than 80 nm. The higher order mode is LP _02, the chromatic dispersion compensating optical fiber of the higher order modes of claim 24.   26. The high-order mode chromatic dispersion compensating optical fiber according to claim 24, wherein a ratio of the chromatic dispersion to the dispersion gradient is larger than 120 nm.   A higher-order mode chromatic dispersion compensating optical fiber having a core having at least five core segments, to which a core cladding is added, and at a wavelength of 1,550 nm, simultaneously, −300 ps / nm · A higher order mode chromatic dispersion compensating optical fiber having a negative chromatic dispersion lower than km and a ratio of chromatic dispersion to dispersion slope greater than 200 nm. The higher order mode is LP _02, the chromatic dispersion compensating optical fiber of the higher order modes of claim 27.

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