KR100769268B1 - A signal distribution network for distributing signal to a plurality of user equipments, optical fiber and optical cable therefor - Google Patents

Abstract

According to the present invention, a signal distribution network 100 for distributing signals to a plurality of user equipments includes a distribution device 40 and a plurality of optical cables formed such that the distribution device 10 communicates with the plurality of user equipments 42. (1) is provided. In turn, each optical cable 1 has an optical fiber 10 having a core 14, a cladding 12 and a predetermined simple refractive index profile Δn (r). Each optical fiber 10 is suitable for ensuring single mode propagation at wavelengths greater than about 1260 nm and several mode propagation at about 850 nm, with each optical fiber having a macro bending loss at about 1550 nm and less than about 0.5 dB. It has this refractive index profile Δn (r) to ensure intermode delay Δτ at 850 nm, which is less than or equal to 1 ns / Km.

Network, Fiber, Macro Bending Loss, Index Profile

Description

A signal distribution network for distributing signal to a multiple of user equipments, optical fiber and optical cable therefor}

The present invention relates to a signal distribution network from a common branch having a distribution device and a plurality of optical fiber cables to a plurality of user equipments.

The invention also relates to an optical fiber cable and an optical fiber formed for use in a signal distribution network.

Currently, optical technology in the field of telecommunications is mainly used for the long-distance transmission of optical signals using the known properties of broadband provided by optical fibers. In contrast, it distributes signals to multiple users (such as television and / or analog and / or digital telephone signals, for example) and distributes digital data among electronic equipment (such as personal computers on a LAN network). Recently used technology for transmission uses, for example, electrical cables such as coaxial cables or cables composed of copper pairs.

Nevertheless, electrical cables have a relatively narrow band and bottleneck the signal band being transmitted. In addition, electrical cables present problems of electromagnetic interference and impedance matching, and stiffness makes them difficult to introduce into certain raceways in buildings. In addition, the volume is large, which significantly reduces the number of cables that can be inserted into the conduit. Moreover, due to electrical safety requirements, electrical cables require the provision of wiring away from the cables used for distributing electrical energy.

Thus, the present study set out to exploit the use of optics in signal distribution networks, as well as in long distance signaling, from a common fork to multiple users. In fact, fiber optic cables are not too bulky, flexible, lightweight and free of electromagnetic interference, making them suitable for insertion into specific wiring conduits in buildings. In addition, optical fiber cables are suitable for insertion into the same conduit line used for electrical energy dissipation. Moreover, optical fibers are potentially very wide bands, have low attenuation values, and are transparent to bit rates, formats, and transmission codes.

Furthermore, among the various forms of optical fibers, conventional single mode optical fibers are more preferable than multimode because they have low absorption loss and are inexpensive; Single-mode fiber is formed for use in WDM transmission and has a wider band.

In general, according to the ITU-T G652 standard, a conventional single mode optical fiber has a cutoff wavelength comprised between 1100 nm and 1280 nm, and a single (of a signal wavelength greater than the cutoff wavelength) and a second or third optical fiber transmission window. It is used with a laser source and detector operating at about 1300 nm and / or 1550 nm to allow transmission in mode propagation.

Nevertheless, due to the relatively high cost of optoelectronics and optical components (eg, such as light sources and detectors) operating at about 1300 nm and / or 1550 nm, conventional single mode optical fibers operating in single mode propagation conditions Distribution networks, including, are not very price competitive for conventional networks using electrical cables.

Thus, while conventional single-mode optical fibers show several advantages, the use of optical fibers in signal distribution networks for large numbers of users has so far been limited.

In order to overcome the above disadvantages, it has been proposed to implement a signal transmission line with a conventional single mode optical fiber at 1300 nm and a laser source and detector operating at about 800 nm, that is, an optical fiber operating under multimode propagation conditions. a. G.A. Bogert ("Signal transmission with optical carriers in multimode range of single-mode fibers"), Electronics Letters, January 1987, Vol. 23, No. 2, pages 71-73; F.J. FJ Gillham et al. ("Single mode fiber optic transceiver using short wavelength active devices in long wavelength fiber" SPIE Fiber Networking and telecommunication, 1989, Vol. 1179, pages 26-33; V.C.W.S. (VCY So et al.) ("Multiple wavelength bidiretional transmission for subscriber loop applications", Electronics Letters, January 1989, Vol. 25, No. 1, pages 16-19) and Ko-ichi Suto, et al. et al.) (“0.78 μm digital transmission characteristics using 1.3 μm optimized single-mode fiber for subscriber loop”, Electronics and Communicaitons in Japan, Part 1, 1992, Vol. 75, No. 2, pages 38-47).

In fact, the transmission lines take advantage of the above advantages of single-mode fiber and at the same time cost is reduced because laser sources and detectors operating at about 800 nm are much cheaper than laser sources and detectors operating at about 1300 nm or 1550 nm. .

Nevertheless, when used in multimode propagation conditions, an optical fiber is a temporary transient of optical pulses propagating in the fiber by moving two different propagation modes (e.g., basic mode LP ₀₁ and first higher order mode LP ₁₁ ) at different group velocities. As it causes widening, a known intermodal dispersion phenomenon is exhibited.

Thus, in an optical fiber transmission line operating under multimode propagation conditions, intermode dispersion limits the maximum data rate (i.e. bit rate) or the maximum length of the line.

Some methods have been proposed to reduce intermode dispersion.

M. M. Romeiser et al. ("Sources and systems: 800 nm transmission on 1300 nm SM fiber", FOC / LAN '87 & MFOC-WEST, pagg. 388-3891); M. Stern et al. (M. Stern et al. ("Three-channel, high-speed transmission over 8 km installed, 1300 nm optimized single-mode fiber using 800 nm CD laser and 1300/1500 nm LED transmitters", Electronics Letters, February 1988, Vol. 24, No. 3, pages 176-177); JL McNaughton et al. ("A compact-disc laser system for video single-mode fiber distribution in the subscriber loop", FOC / LAN '' 88, pages 231-233; M. Stern et al. (“Short-wavelength transmission on 1300 nm optimized single-mode fiber”. Optical Engineering, October 1988, Vol. 27, No. 10, pages 901-908) and H. Jorring ("Design of optical fiber for single-mode transmission at 800 nm", E-FOC / LAN '91, pages 105-108) are conventional optical fiber single at 1300 nm. Mode and laser source emitting at 800/850 nm (e.g., Compaq It discloses a local transmission system having a mode filter (modal filter) for removing a disc or a laser for CD) and high-order mode.

K. A. H. KAH van Leeuwen et al. ("Measurement of higher-order mode attenuation in single-mode fibers: effective cutoff wavelength", Optics Letters, June 1984, Vol. 9, No. 6, pages 252-254 ) Shows that a single-mode fiber-optic communication system can operate below the LP ₁₁ mode's theoretical cutoff wavelength if the attenuation of the transmitted light in LP ₁₁ mode significantly reduces the effects of mode noise and intermode dispersion. To do this, we introduce a method for determining the attenuation coefficient according to the wavelength of LP ₁₁ mode in a single mode optical fiber.

K. Kitayama et al. ("Experimental verification of modal dispersion free characteristics in a two-mode optical fiber", IEEE Journal of Quantum Electronics, January 1979, Vol. QE-15, No. 1, pages 6 -8) discloses theoretical and experimental measurement results formed to measure group delays in LP ₀₁ and LP ₁₁ modes in a stepped optical fiber along one wavelength region, where the optical fiber only guides the two modes. do. The results obtained indicate that the group delays of the two modes have matching wavelengths.

U.S. Patent No. 4 955 014 proposes an optical waveguide communication system in the subscriber area, where a conventional single mode optical waveguide optimized for propagation in the range of 1300 nm to 1600 nm has an optical transmitter whose operating wavelength is below the waveguide cutoff wavelength. And a receiver. This waveguide is coupled to the laser to activate a single propagation mode that allows high bit rate digital signal transmission.

US Patent No. 4 204 745 discloses a graded index optical fiber having a distribution of refractive index n as a function of radial distance r from the core axis presented below;

Where n ₀ is the refractive index in the core axis, a is the core radius, α is the power factor, and Δ = (n ₀ -n _e ) / n _e and n _e are the cladding refractive indices. In the fiber, the power index α and the normalized frequency ν [ν = (2πan ₀ / λ) × (2Δ) ^1/2 ] are selected such that the group delay of the basic mode is equal to the group delay of the first higher-order mode.

Applicants have found that the patent relates to radiation transmission in multimode, preferably two mode, propagation conditions, especially at 1.25 μm wavelength, and does not disclose or suggest the use of fibers in single mode propagation conditions.

U.S. Patent No. 4 877 304 discloses that the refractive index n ₀ at the core axis, the refractive index n ₁ of the cladding, the core radius a and the core refractive index profile are (a) normalized with the normalized delay time of the j th mode (j = 1 or 2). The difference between the normalized delay times of the modes is less than about 5 × 10 ⁻² for a wide range of normalized frequencies V [V = (n ₁ ² -n ₀ ² ) ^1/2 × (2πa) / λ] (b The normalized waveguide variance is chosen to be less than or equal to 0.2 at a V value near the normalized cutoff frequency of the first higher order mode. Due to the limited number of variables in the stepped refraction profile or α design in the patent specification, it is not expected that a fiber with the refractive index profile will satisfy both conditions (a) and (b). . An example of a fiber that can satisfy the above condition is, for example, a W-shaped fiber having a fragmented core index profile. An optical fiber having the above features (a) and (b) has a bandwidth comprised between 2 GHz × Km and 4 GHz × Km and a signal having 2 or 3 modes over a wavelength range between 800 nm and 900 nm and more than 1250 nm. At higher wavelengths it can propagate low distributed monomode signals (total dispersion less than 5 ps / Km × nm).

In that patent, the fiber can be used in several system applications. For example, firstly, if the bandwidth requirement is contained between 2 GHz × Km and 4 GHz × Km, the system using the optical fiber can be operated at a wavelength comprised between 800 nm and 900 nm where the optical fiber guides several modes. Take advantage of using low cost sources and connectors. On the other hand, if bandwidth requirements are later increased, the system can be upgraded by using source equipment and detectors operating in the low-distributed single-mode region of the optical fiber and terminal equipment operating at higher bit rates.

Nevertheless, Applicants have found that the optical fiber actually disclosed by US Pat. No. 4,877,304 is very difficult and expensive to manufacture. Therefore, it is used in an optical fiber distribution network where cost factor is very important, which is not suitable.

Jun-ichi Sakai et al. ("Large-core, broadband optical fiber", OPTICS LETTERS, Vol. 1, No. 5, 1977, pages 169-171) are the cores of conventional single-mode optical fibers. A bimodal broadband optical fiber having a core diameter larger than the diameter is disclosed. Sakai et al. Select a normalized frequency of 4.6 and a refractive index profile parameter α of 4.5, whereby a core diameter of about 16.3 μm in size with a refractive index difference of 0.3% at a wavelength of 1.25 μm can be obtained.

Applicants are initially suited for use at wide bandwidths at about 850 nm in multimode propagation conditions that are cost-competitive for conventional distribution networks using electrical cables when the bandwidth requirements are relatively limited, and later, bandwidth requirements. When this increased, the technical problem of providing a signal distribution network in a simple and effective manner suitable for upgrading to operate in a very wide band of single mode propagation conditions at about 1300 nm and 1550 nm was encountered.

Thus, in a first aspect, the present invention includes a distribution device and a plurality of optical cables configured to communicate with a plurality of user equipment, each optical cable having a core, cladding and a predetermined simple refractive index profile Δn (r). Wherein Δn (r) means the difference in refractive index between the core and the cladding as a function of radial distance r, and each optical fiber is monomode propagated at wavelengths greater than about 1260 nm. Is a signal distribution network for distributing signals to a plurality of user equipments configured to provide multimode propagation at about 850 nm, wherein the refractive index profile Δn (r) of each optical fiber is 100 times on a principal axis having a diameter of 60 mm. Macro bending loss at 1550 nm which is less than about 0.5 dB after rotation; To provide an intermode delay Δτ at 850 nm that is about or less than about 1 ns / Km.

In the specification and in the claims that follow,

&Quot; Multimode propagation " is used to indicate the optical fiber propagation of the basic mode LP ₀₁ and the first higher order mode LP ₁₁ and optionally, the second higher order mode LP ₀₂ . Nevertheless, the second higher order mode, when present, is significantly disadvantaged by the high attenuation which is susceptible to normal use conditions. Preferably, the expression "multimode propagation" is used to represent two mode optical fiber propagation (of basic mode LP ₀₁ and first higher order mode LP ₁₁ ) to prevent output loss caused by attenuation of the second mode LP ₀₂ . do;

* "Simple refractive index profile" is used to represent a refractive index profile defined by a single radial piece, small dip or diffuse tail of a fiber, independent of possible variations due to the production process.

According to the applicant's recognition, by optimizing both the transmission capacities of the multimode propagation conditions at 850 nm and the single mode propagation conditions at 1550 nm, it is possible to obtain an upgradeable multiwavelength optical distribution network having a very wide band.

The optical fiber of the distribution network of the present invention is formed to operate at several propagation conditions at 850 nm with an intermode delay Δτ of less than about 1 ns / Km, thus inexpensive optical components and / or optoelectronics operating at 850 nm with high bandwidth. Allow the use of parts in an effective manner.

In addition, the optical fiber of the distribution network of the present invention has a macro bending at 1550 nm that is less than 0.5 dB after 100 rotations of a fiber wound around a 60 mm diameter main axis (corresponding to about 26 dB / Km) with respect to the basic propagation mode LP ₀₁ . Has a loss.

Moreover, since the macro bending loss for the propagation mode has been proved to increase with increasing wavelength, the optical fiber of the network of the present invention has a macro bending loss which is also less than 0.5 dB at 1300 nm and 850 nm for the basic propagation mode LP. Has

Applicants have found that the optical fiber of the present invention, having a bending loss of less than 0.5 dB at 1550 nm, has the undesired effect of the hard conditions in which the fiber in the distribution network is susceptible to both multimode propagation conditions and single mode propagation conditions. Significantly reduced. In fact, in a distribution network installed in a building, due to the winding path to the conduit into which the optical fiber is inserted, the presence of other electrical or optical cables in the conduit and the pressure on the inner wall of the conduit, the optical fiber is subject to strong stress and bending on the raw surface. , Torsional, and lateral pressures are susceptible to strong attenuation of the signals propagating into the fiber.

In particular, the Applicant has found that a fiber having the above characteristics provides a low bending loss under severe use conditions, such as a form installed in a building up to at least 1625 nm wavelength, and allows transmission up to the upper limit of the transmission band at 1550 nm.

Thus, the distribution network of the present invention is advantageously formed for low cost and effective operation (at about 850 nm) under multimode propagation conditions (Δτ less than 1 ns / Km and bending loss lower than 0.5 dB at 850 nm), single mode. It can be upgraded to work effectively in propagation conditions (bending loss lower than 0.5 dB at 1300 nm and 1550 nm).

First, when bandwidth requirements are relatively limited, the distribution network of the present invention is thus formed to be used at low cost in broadband multimode propagation conditions, and is cost competitive with conventional distribution networks using electrical cables. It is also suitable for later upgrades to operate over a wide range of single mode propagation conditions when bandwidth requirements increase.

In particular, the distribution network of the present invention directly allows the end user to optically transmit signals transmitted by one or more suppliers at any wavelength of one or more of the three bands at 850 nm, 1300 nm, and 1550 nm.

Moreover, since the optical fiber of the present invention has a simple refractive index profile, the optical fiber can be well compatible with a single mode optical fiber conforming to the ITU-T G652 standard having a simple refractive index profile.

In addition, the optical fiber of the present invention having a simple refractive index profile is easy to manufacture and guarantees low production cost and low defects.                 

Preferably, the intermode delay Δτ at a wavelength of 850 nm is less than about 0.5 ns / Km. More preferably, the intermode delay Δτ at a wavelength of 850 nm is less than about 0.05 ns / Km.

Preferably, the macro bending loss at a wavelength of 1550 nm after 100 rotations on a major axis having a 60 mm diameter is less than about 0.2 dB.

Preferably, the optical fibers of the distribution network of the present invention have a microbending loss of less than about 15 [(dB / Km) / (g / mm)] at a wavelength of 1550 nm. More preferably, it has a micro bending loss of less than about 10 [(dB / Km) / (g / mm)] at a wavelength of 1550 nm.

Micro bending loss is for example. G. Grasso and F. F. Meli ("Microbending losses of cabled sigle-mode fibers", ECOC '88, page 526 and below) or G. It can be measured by the stretchable coil method disclosed by Grasso et al. (“Microbending effects in single-mode optical cables”, International Wire and Cable Symphosium, 1988, page 722 and below).

The cladding of each optical fiber has a lower refractive index relative to the refractive index of the core, thereby allowing the transmitted signal to be limited to the core.

Generally, both the core and the cladding are silica based glass materials (n is about 1.46) and the difference in refractive index between the core and the cladding is determined by the addition of a suitable additive (dopant) to the core and / or to obtain a predetermined refractive index profile Δn (r). It is obtained by including in the glass matrix of the cladding.

Examples of common dopants are fluorine, phosphorus and germanium.

From the measurement of the refractive index profile of actual fibers carried out according to known methods, in particular of fibers produced by "external vapor deposition" (OVD) or "vacuum axial deposition" (VAD) production methods, It is possible to determine the normalized frequency values V and Δn ₀ values accordingly.

Preferably, each optical fiber has a normalized frequency value V at 850 nm (defined below) comprised between about 3.0 and 3.6. More preferably, the frequency value is comprised between about 3.2 and 3.6.

In general, each optical fiber has a Δn ₀ value comprised between 5 × 10 ⁻³ and 7 × 10 ⁻³ .

Advantageously, the area determined by integrating the value of the difference in refractive index between the core and the cladding by a semi-area bound by the refractive index profile (ie r ranging from 0 to a radial value corresponding to the cladding). ) Is about 0.017 μm or more. Preferably, it is about 0.018 micrometers or more.

Advantageously, the core radius of each optical fiber defined according to the ITU-T G650 standard is comprised between 3 μm and 6 μm. This means that the optical fiber of the present invention generally has a radius comprised between 4 μm and 6 μm and is a single mode optical fiber according to the ITU-T G650 standard, and a laser source having (eg, a conventional optical fiber pigtail) It is highly compatible with devices used in conventional optical fiber telecommunication systems (such as optical connectors optimized for connecting conventional single mode optical fibers) and equipment for measuring optical and / or optoelectronic components.

Advantageously, each optical fiber outside the cladding is provided with an outer protective coating which is generally made of a two-layer polymeric material.

In general, the diameter of the outer protective coating is about 250 μm. In addition, the outer diameter of the cladding is generally about 125 μm.

Preferably, the material of at least a portion of the outer coating in contact with the outer coating or cladding has a refractive index greater than that of the cladding. It is commonly excited, for example, in fiber optics with splices, connections, or warpage, and may cause cladding mode stripping (“mode stripping”), which degrades system performance when the cladding modes are left to propagate to the receiver. To advantage.

More preferably, the refractive index of the material constituting the outer coating is higher than the refractive index of the cladding when the temperature varies in the temperature range generally comprised between 10 ° C. and 60 ° C. This allows to ensure the suppression of the cladding mode also at varying temperature conditions. This is advantageous because in optical signal distribution networks installed in buildings, optical fibers are generally subjected to temperature changes due to, for example, the arrangement of optical fibers in the vicinity of electrical cables, heat sources for home heating purposes, hot water mains, or electrical equipment.

According to another solution, the external protective coating is composed of a material capable of strongly absorbing electromagnetic radiation at the relevant wavelengths, thereby suppressing possible cladding modes.

Advantageously, the optical fiber of the network of the present invention, in multimode propagation conditions, transmits an optical signal of bit rate of 2.5 Gbit / s or more on a link of about 300 m length.

Advantageously, each optical cable also has a second optical fiber.

For the structural and functional features of the second optical fiber, reference will be made directly to the above disclosed optical fiber.

In general, on the user side, the network of the present invention also includes a plurality of optoelectronic converters in communication with the plurality of optical cables.

Each optoelectronic converter is configured to convert an optical signal from an associated optical cable into a corresponding electrical signal for sending to a corresponding user equipment.

In general, each optoelectronic converter includes a photodetector.

In a bidirectional embodiment, each optoelectronic converter is also configured to convert electrical signals from associated user equipment into corresponding optical signals for sending to corresponding optical cables. In this case, each optoelectronic converter also has a light source.

In general, to operate in multimode propagation conditions of an optical fiber, the light source is configured to operate at a wavelength comprised between about 820 nm and 870 nm. Preferably, it is formed to operate at a wavelength comprised between about 830 nm and 860 nm. More preferably, it is formed to operate at a wavelength of about 850 nm.

According to a variant, in order to operate in a single mode propagation condition of an optical fiber, the light source is formed to operate at a wavelength comprised between about 1300 nm and 1625 nm.

Generally, on the distribution device side, the network of the present invention also includes a plurality of optoelectronic converters in communication with the plurality of optical cables.

Each optoelectronic converter is configured to convert an electrical signal from the distribution device into a corresponding optical signal for sending to an associated user equipment via a corresponding optical cable.

In general, each optoelectronic converter includes a conventional light source.

In general, to operate in multimode propagation conditions of an optical fiber, the light source is configured to operate at a wavelength comprised between about 820 nm and 870 nm. Preferably, it is formed to operate at a wavelength comprised between about 830 nm and 860 nm. More preferably, it is formed to operate at a wavelength of about 850 nm.

According to a variant, in order to operate in a single mode propagation condition of an optical fiber, the light source is formed to operate at a wavelength comprised between about 1300 nm and 1625 nm.

In a bidirectional embodiment, each optoelectronic converter is further configured to convert an optical signal from user electronics into a corresponding electrical signal via an associated optical cable.

In this case, each optoelectronic converter generally includes a photodetector.

A common example of a conventional light source is a vertical cavity surface emitting laser (VCSEL) laser source that emits at about 850 nm or about 1310 nm. Also, general examples of conventional light sources emitting in the range of 1300 nm to 1350 nm-1350 nm or 1480 nm-1625 nm are Fabry-Perot lasers and DFB or DBR semiconductor lasers.

A common example of a conventional photodetector is a photodiode in particular of PIN type.

In general, the distribution signal is digital.                 

Generally, optical cable lengths are less than about 2 km, taking into account the usage provided for distribution of signals to end users, starting from a common branch point. Preferably, the length of the optical cable is less than 1 km. More preferably less than 300 m.

According to an embodiment, at the user side, the distribution network of the invention comprises at least one domestic network connected to the corresponding optical cable. In general, home networks are star type or bus type.

The home network is configured to send signals from connected optical cables to a number of user equipments, for example, to a plurality of user equipment located in a user's home.

In this case, the network distribution apparatus of the present invention is configured to multiplex a plurality of signals of wavelengths according to one wavelength division multiplexed (or WDM) optical signal and to send WDM optical signals along the optical cable.

In general, a home network wavelength-demultiplexes a WDM optical signal entering an input into a plurality of signals of different wavelengths and transmits the plurality of signals to an optoelectronic converter connected to other user equipment. And an optical coupler.

According to a variant, the home network is configured to distribute the output of the WDM optical signal entering the input and send a portion of the obtained output of the WDM optical signal to an optoelectronic converter connected to other user equipment. In this case, the optoelectronic converter also advantageously comprises a filter for extracting from the WDM optical signal the wavelength carrying the intended information for the associated user equipment.

In a second aspect, the invention also includes at least one optical fiber having a core, cladding and a predetermined simple refractive index profile Δn (r), wherein Δn (r) is a function of radial distance r. A refractive index difference between the cladding and the cladding, wherein the at least one optical fiber is suitable for use in signal distribution networks formed to ensure single mode propagation at wavelengths greater than about 1260 nm and multimode propagation at about 850 nm. In an optical cable, the at least one optical fiber has a macro bending loss at 1550 nm of less than about 0.5 dB after 100 rotations on a principal axis having a diameter of 60 mm, and an intermode delay Δτ at 850 nm of about 1 ns / Km or less. To ensure this refractive index profile Δn (r).

Preferably, the cable also includes a second optical fiber.

For the structural and functional features of the optical fiber and the optical cable, reference will be made to what has been disclosed above for the distribution network of the present invention.

In a third aspect, the invention also has a core, cladding and a predetermined simple refractive index profile Δn (r), wherein Δn (r) is a function of the refractive index difference between the core and the cladding as a function of radial distance r. An optical fiber suitable for use in a signal distribution network configured to provide monomode propagation at wavelengths greater than about 1260 nm and multimode propagation at about 850 nm, the optical fiber being 100 times on a principal axis having a diameter of 60 mm. It has a refractive index profile Δn (r) to ensure a macro bending loss at 1550 nm that is less than about 0.5 dB after rotation and an intermode delay Δτ at 850 nm that is less than or about 1 ns / Km.

With regard to the structural and functional features of the optical fiber, reference will be made to what has been disclosed above in conjunction with the distribution network of the present invention.

Further features and advantages of the present invention will become more apparent from the following detailed description of preferred embodiments made with reference to the accompanying drawings.

1 is a first example of the refractive index profile Δn (r) of an optical fiber according to the present invention;

2 is a second example of the refractive index Δn (r) of the optical fiber according to the present invention;

3 is a schematic diagram of a signal distribution network according to the present invention;

4 is a schematic diagram of a first embodiment of a signal distribution network of the present invention;

5 is a schematic diagram of a second embodiment of a signal distribution network of the present invention;

6 is a schematic diagram of a third embodiment of a signal distribution network of the present invention;

FIG. 7 is a modified schematic view of the third embodiment of FIG. 6;

8 is a distribution network of the present invention installed in a building with wiring conduits for passage of optical cables;

9 is an embodiment of an optical fiber according to the present invention;

10 shows the refractive index profile Δn (r) of an optical fiber according to the present invention manufactured by the applicant;

11 (a)-(c) show three examples of the beta form of the refractive index Δn (r).

12 is a schematic diagram of a fourth embodiment of a signal distribution network of the present invention;

FIG. 13 shows the pattern of form factor g as a normalized frequency change for inter mode delay values obtained with a beta form of refractive index profile and less than or equal to 1 ns / Km;

14 shows the pattern of bending loss as the corresponding reflectance zone by the refractive index profile change obtained with the beta profile;

15 (a)-(c) are three or more examples of the beta form of the refractive index Δn (r);

16 (a)-(c) are three or more examples of the beta form of the refractive index Δn (r);

17 (a)-(c) are two or more examples of the beta form of the refractive index Δn (r).

9 shows an embodiment of an optical fiber 10 according to the present invention, in which the optical fiber has an inner region 14 called a core through which the optical signal is transmitted and an outer annular region 12 called cladding. . The cladding 12 has a lower refractive index relative to the refractive index of the core 14 and thus limits the transmitted signal to the core.

In general, both the core 14 and the cladding 12 are made of a silica-based glass material, and the difference in refractive index between the core 14 and the cladding 12 may result in an appropriate additive (dopant) being added to the core 14 and / or the like. Or by including it in the glass matrix of the cladding 12.

Based on the radial distribution of the dopant in the core 14 and cladding 12 of the optical fiber 10, a predetermined refractive index profile Δn (r) is obtained, wherein Δn (r) is the longitudinal direction of the optical fiber 10. The refractive index difference between the core 14 and the cladding 12 as a function of the radial distance r from the axis XX.

In general, as shown in the examples disclosed below, the cladding 12 is made of substantially pure silica and has a substantially constant refractive index n ₀ even if the radial distance from the axis XX changes.

The optical fiber 10 according to the present invention is selected in the following manner with a cutoff wavelength and a simple refractive index Δn (r) for the first higher order mode LP ₁₁ and the second higher order mode LP ₀₂ .

Monomode propagation at wavelengths greater than about 1260 nm, ie the 2 m fiber cutoff wavelength (ITU-T G652) of the first higher-order mode LP _{11 that} is less than about 1260 nm;

- Several mode propagation at about 850 nm—ie, a 2m fiber cutoff wavelength (ITU-T G652) of the first higher-order mode LP _{11 that} is greater than about 850 nm;

A macrobending loss at a wavelength of 1550 nm which is less than about 0.5 dB after 100 revolutions of the fiber around the major axis having a diameter of 60 mm; And

Provide an intermodal delay Δτ between the basic propagation mode LP ₀₁ and the first higher-order mode LP _{11 at} or about 1 ns / Km at a wavelength of about 850 nm.

Further, the 2m fiber cutoff wavelength (ITU-T G652) of the second higher order mode LP ₀₂ is preferably less than about 800 nm.

For example, in general theory a simple refractive index profile, hereinafter referred to as a "beta profile"-"external vapor deposition" (or outside vapor deposition) and "vapor deposition" (or VAD, vapor axial deposition) It is similar to the actual refractive index profile obtained by conventional methods for the production of optical fibers, known as N-), with a small dip in the center of the core 14 (representing the OVD production process) that initially has a parabolic pattern but is later flattened. A central portion having a super Gaussian pattern and an outer tail having a Laurentzian pattern, wherein the super Gaussian pattern is represented by a curve diagram defined by the following formula;

Where r is the radial distance from the longitudinal axis XX of the optical fiber 10, a and g are the two parameters of the radial dimension and the pattern form, and the Lorentian pattern is given by the curve diagram defined in the equation Become;

Where r is the radial distance from the longitudinal axis XX of the optical fiber 10, and parameters A, w and x _c are the foam parameters selected such that the Lorentian cove intersects the central super Gaussian portion at the inflection point of the Gaussian portion.

Applicants note that the frequency V at which the intermode delay Δτ is normalized at 850 nm between the basic propagation mode LP ₀₁ and the first higher-order mode LP ₁₁ , the form parameter g of the central super Gaussian portion of the beta profile, and the small dip of the beta profile in general, It is noted that it depends on the parameters defining the super Gaussian part and Lorenchian cove.

Normalized frequency V is defined as follows;

Where Δn ₀ is the maximum refractive index difference between the core 14 and the cladding 12, n is the refractive index of the silica (about 1.46), and a is the core radius.

For the beta profile, Δn ₀ corresponds to the value taken by the super Gaussian curve interpolating for a r value of zero, where a is the radial parameter of the super Gaussian curve.

Applicants also noted that the macro bending loss depends on the parameters defining the semi- and beta profiles of small dips, super Gaussian portions, and Lorentian tails defined by a simple refractive index profile.

Thus, computer simulations show that the super-Gaussian pattern of the beta profile is such that when the normalized frequency V at 850 nm changes with respect to other values of the parameters of the beta profile, the g-value is obtained to obtain an intermode delay Δτ of less than 1 ns / Km at 850 nm. Was performed to determine the value of the form parameter g of the central part with.

In addition, computer simulations show that 1550 nm obtained from 100 turns of fiber wound around a major axis having a diameter of 60 mm for a fiber having a beta refractive index profile when the semi-region corresponding to the profile changes for different values of the beta profile parameter. Was performed to measure the loss of macro bending at.

FIG. 13 shows the value of the form parameter g when the normalized frequency obtained by simulation changes.

In FIG. 13, line 500 represents the normalized cutoff frequency of the first higher-order mode LP ₁₁ , while line 501 represents the normalized cutoff frequency of the second higher-order mode LP ₀₂ ; That is, the two lines 500, 501 define a two mode propagation area (of the basic mode LP ₀₁ and the first higher order mode LP ₁₁ ) within the line. Moreover, line 502 constitutes an area in which points (V, g) corresponding to a beta profile having an intermode delay of 1 ns / Km or less are dense, and line 503 is an intermode delay of 0.5 ns / Km or less. The points (V, g) corresponding to the beta profile having a dense region are formed, and the line 504 is close to the points (V, g) corresponding to the beta profile with an intermode delay of about 0.05 ns / Km or less. To form an area.

 As noted, for optical fibers having a beta-type refractive index profile to have an intermode delay Δτ less than 1 ns / Km, the frequency V normalized at 850 nm should be included between about 2.85 and about 3.95. Preferably, the normalized frequency V is comprised between about 3.0 and about 3.6. More preferably, between about 3.2 and about 3.6. In this last case, the value of the form parameter g is preferably 9 or less.

In turn, FIG. 14 shows the macro bending loss at 1550 nm, expressed in dB after 100 revolutions of the fiber wound around a major axis having a diameter of 60 mm as the corresponding semi-area A by the profile change obtained in the simulation. (L) is shown.                 

The upper region consists of points (A, L) corresponding to the beta profile with macro bending loss greater than 0.5 dB after 100 turns of fiber wound around the 60 mm spindle, and the macro bending loss lower than 0.5 dB. Two regions of the lower region consisting of points A and L corresponding to the beta profile having can be noted in FIG. 14.

  As noted, for an optical fiber having a beta-shaped refractive index profile to have a macrobending loss lower than 0.5 dB, the semi-region corresponding to the profile should have a value greater than about 0.017 μm. Preferably, the semi-region corresponding to the profile has a value greater than about 0.018 μm.

11 (a)-(c), 15 (a)-(c), 16 (a)-(c) and 17 (a)-(b)

Monomode propagation at wavelengths greater than about 1260 nm;

Multimode propagation at about 850 nm;

Macro bending loss at 1550 nm which is less than about 0.5 dB after 100 rotations of the fiber around the major axis having a 60 mm diameter; And

11 examples of beta profiles that provide an intermode delay Δτ between the basic propagation mode LP ₀₁ and the first higher-order mode LP ₁₁ at about 850 nm, which is about 1 ns / Km or less.

The main features of the beta profiles shown in FIGS. 11 (a)-(c), 15 (a)-(c), 16 (a)-(c) and 17 (a)-(b) are shown in Table 1 It is shown at -4.

characteristic 11 (a) 11 (b) 11 (c) Δn ₀ 5.9 × 10 ^-3 5.8 × 10 ^-3 6.6 × 10 ^-3 a (μm) 3.5 3.6 3.4 g 4 2.7 3.4 Δτ (ns / Km) at 850 nm 0.02 0.02 0.019 Semi Area (㎛) 0.020 0.020 0.020 Normalized Frequency V 3.38 3.53 3.45 λ cutoff LP ₁₁ (nm) 1204 1244 1177 λ cutoff LP ₀₂ (nm) 808 843 779 Color Dispersion at 1550 nm [ps / (nm × Km)] 14.5 15.4 13.3 Mode field diameter at 850 nm (μm) 6.5 6.8 6.2 Mode field diameter at 1550 nm (μm) 9.8 10.2 9.3 Macro bending LP ₀₁ at 850 nm (dB after 60 turns with 100 mm diameter) <10 ^-3 <10 ^-3 <10 ^-3 Macro bending LP ₀₁ at 1550 nm (dB in 60 mm diameter and 100 revolutions) 0.6 × 10 ^-3 0.9 × 10 ^-3 <10 ^-3 Macro bending LP ₁₁ at 850 nm (60 mm diameter, dB after 100 revolutions) 0.3 × 10 ^-3 0.2 × 10 ^-3 <10 ^-3 Micro bending at 1550 nm [(dB / Km) / (g / mm)] 3.9 4.9 2.4

characteristic 15 (a) 15 (b) 15 (c) Δn ₀ 6.8 × 10 ^-3 5.3 × 10 ^-3 5.3 × 10 ^-3 a (μm) 3.3 3.5 3.5 g 3.5 4.0 5.7 Δτ (ns / Km) at 850 nm 0.03 0.01 0.03 Semi Area (㎛) 0.022 0.019 0.019 Normalized Frequency V 3.47 3.24 3.23 λ cutoff LP ₁₁ (nm) 1226 1208 1177 λ cutoff LP ₀₂ (nm) 824 835 792 Color Dispersion at 1550 nm [ps / (nm × Km)] 13.86 15.3 14.65 Mode field diameter at 850 nm (μm) 6.2 7.0 6.7 Mode field diameter at 1550 nm (μm) 9.2 10.7 9.3 Macro bending LP ₀₁ at 850 nm (dB after 60 turns with 100 mm diameter) <10 ^-3 <10 ^-3 <10 ^-3 Macro bending LP ₀₁ at 1550 nm (dB in 60 mm diameter and 100 revolutions) <10 ^-3 0.05 0.02 Macro bending LP ₁₁ at 850 nm (60 mm diameter, dB after 100 revolutions) <10 ^-3 0.06 0.04 Micro bending at 1550 nm [(dB / Km) / (g / mm)] 1.9 9.0 6.9

characteristic 16 (a) 16 (b) 16 (c) Δn ₀ 5.0 × 10 ^-3 7.2 × 10 ^-3 7.5 × 10 ^-3 a (μm) 3.5 2.9 2.8 g 6.9 7.0 8.9 Δτ (ns / Km) at 850 nm 0.04 0.03 0.01 Semi Area (㎛) 0.018 0.022 0.022 Normalized Frequency V 3.18 3.19 3.15 λ cutoff LP ₁₁ (nm) 1162 1162 1170 λ cutoff LP ₀₂ (nm) 783 780 816 Color Dispersion at 1550 nm [ps / (nm × Km)] 14.70 11.71 11.18 Mode field diameter at 850 nm (μm) 6.8 5.7 5.6 Mode field diameter at 1550 nm (μm) 10.5 8.7 8.6 Macro bending LP ₀₁ at 850 nm (dB after 60 turns with 100 mm diameter) <10 ^-3 <10 ^-3 <10 ^-3 Macro bending LP ₀₁ at 1550 nm (dB in 60 mm diameter and 100 revolutions) 0.11 <10 ^-3 <10 ^-3 Macro bending LP ₁₁ at 850 nm (60 mm diameter, dB after 100 revolutions) 0.3 <10 ^-3 <10 ^-3 Micro bending at 1550 nm [(dB / Km) / (g / mm)] 9.1 1.4 1.25

characteristic 17 (a) 17 (b) Δn ₀ 6.6 × 10 ^-3 5.1 × 10 ^-3 a (μm) 3.1 3.4 g 9.2 10.7 Δτ (ns / Km) at 850 nm 0.04 0.04 Semi Area (㎛) 0.021 0.018 Normalized Frequency V 3.18 3.08 λ cutoff LP ₁₁ (nm) 1184 1151 λ cutoff LP ₀₂ (nm) 828 815 Color Dispersion at 1550 nm [ps / (nm × Km)] 12.51 13.98 Mode field diameter at 850 nm (μm) 5.9 6.6 Mode field diameter at 1550 nm (μm) 9.1 10.4 Macro bending LP ₀₁ at 850 nm (dB after 60 turns with 100 mm diameter) <10 ^-3 <10 ^-3 Macro bending LP ₀₁ at 1550 nm (dB in 60 mm diameter and 100 revolutions) <10 ^-3 0.11 Macro bending LP ₁₁ at 850 nm (60 mm diameter, dB after 100 revolutions) <10 ^-3 0.58 Micro bending at 1550 nm [(dB / Km) / (g / mm)] 2.1 8.7

In the table above,                 

-"Mode Field Diameter" refers to the mode field diameter according to the ITU-T G650 standard;

"Macro bending with 60 mm diameter" refers to the attenuation in dB that an optical fiber wound 100 times around a major axis having a 60 mm diameter is susceptible;

"Microbending" is the attenuation (dB / Km) introduced by an optical fiber assuming the pressure (expressed in g / mm) on a reference raw surface measured according to the above-described extensible coil method. Say.

From Table 1-4, it can be noted that the chromatic dispersion value is better than the chromatic dispersion value of the optical fiber according to the ITU-T G652 standard. This is advantageous, for example, in the application of optical fibers to medium to long distance optical communication systems in metropolitan systems.

Moreover, MFD values are formed to provide low junction loss, joint loss, and joint loss.

Thus, the optical fiber according to the present invention, in an effective manner, implements a signal distribution network with low cost optoelectronic components (light sources and detectors) and allows it to operate at 850 nm and monomode at about 1300 nm and / or 1550 nm. It can be upgraded to work in an effective manner in the radio field.

1 and 2 show two different examples of the refractive index profile Δn (r) according to the invention for the optical fiber 10 as the radial distance r from the axis XX of the optical fiber 10 changes. .                 

It can be noted that in FIG. 1 and FIG. 2 the refractive index profile is lower than 10 ⁻⁴ at a value of r about 4.65 μm.

Moreover, the semi-regions defined by the refractive index profiles of FIGS. 1 and 2 have values of 0.19 and 0.0179 μm, respectively.

The numerical simulation shows that the theoretical cutoff wavelength λ _c for the first higher propagation mode LP ₁₁ is about 1098 nm for the optical fiber of FIG. 1 and about 1095 nm for the optical fiber of FIG. 2. In turn, the theoretical cutoff wavelength λ _c for the second higher order propagation mode LP ₀₂ was about 715 nm for the optical fiber of FIG. 1 and about 714 nm for the optical fiber of FIG. 2.

Thus, the optical fiber 10 having the refractive index profiles of FIGS. 1 and 2 has a single mode propagation of optical signals in the second and third transmission windows (concentrated around wavelengths of about 1310 nm and 1550 nm, respectively) and 2 at about 850 nm. Allows propagation of two modes (basic mode LP ₀₁ and first higher mode LP ₁₁ ).

Numerical simulations of the propagation of an optical signal in an optical fiber showed that the optical fiber with the refractive index profile of FIGS. 1 and 2 (at a single wavelength of about 850 nm)

The difference Δτ between the propagation delays of the two modes LP ₀₁ and LP ₁₁ is 0.34 ns / Km in FIG. 1 and 0.23 ns / Km in FIG. 2;

The attenuation due to the calculated macro bending for the fiber wound 100 times around the main axis with 60 mm diameter for mode LP ₀₁ was found to be 0.059 dB / Km in FIG. 1 and 1.17 dB / Km in FIG. 2.

Thus, the optical fiber operates at about 850 nm and enables to implement a signal distribution network with low cost optoelectronic components (light sources and detectors) in an effective manner.

Numerical simulations also showed that optical fibers with the refractive index profiles of FIGS. 1 and 2 under single mode propagation conditions (of about 1310 nm and 1550 nm of single wavelength) have the characteristics summarized in Tables 5 and 6, respectively.

At 1310 nm At 1550 nm Color dispersion (ps / (nm × Km)) -4.2 12.5 Chromatic Dispersion Slope (ps / (nm ² × Km)) 0.085 0.059 Mode field diameter (㎛) 8.25 9.66 Effective area (㎛ ² ) 51.5 69.3 Macro bending (60 mm) in diameter <10 ^-3 0.02 Micro Bending (dB / Km) (g / mm) 0.8 2.8

At 1310 nm At 1550 nm Color dispersion (ps / (nm × Km)) -3.4 13.4 Chromatic Dispersion Slope (ps / (nm ² × Km)) 0.086 0.059 Mode field diameter (㎛) 8.76 10.26 Effective area (㎛ ² ) 58.0 78.2 Macro bending (60 mm) in diameter <10 ^-3 0.34

In the table above, "effective area" is defined according to the ITU-T G650 standard.

It can be noted from Tables 5 and 6 that the macrobending values are less than 0.5 dB after 100 turns of fiber wound around a major axis having a 60 mm diameter in both cases.

It can also be noted that from Tables 5 and 6 the chromatic dispersion and chromatic dispersion slope values are equivalent to or better than optical fibers according to the ITU-T G652 standard. This is advantageous, for example, in the application of optical fibers to medium to long distance optical communication systems in metropolitan systems.

Advantageously, the chromatic dispersion at 1550 nm has one or lower of 20, 19, 18, 17, 16 ps / (nm × Km) listed in ascending order.

Moreover, the MFD and effective area values are formed to produce low junction loss, connection loss and coupling loss.

Thus, the optical fiber according to the present invention is effective for signal distribution networks having low cost optoelectronic components (light sources and detectors) that can operate at about 850 nm and can be upgraded to operate in single mode propagation areas of about 1300 nm and / or 1550 nm. To be implemented in such a way.

FIG. 10 shows the experimentally measured actual refractive index profile Δn (r) of the optical fiber 10 according to the invention produced by the applicant.

As noted, the profile is similar to that of the beta form.

The semi-region corresponding to this index profile is about 0.0186 mu m.

Experimental measurements performed on the optical fiber with the exponential profile of FIG. 10 show that the 2m fiber cutoff wavelength (ITU-T G652) for the first higher propagation mode LP ₁₁ of the fiber is about 1069 nm, while the second higher order propagation mode is It was found that the 2m fiber cutoff wavelength (ITU-T G652) for LP ₀₂ was about 690 nm.

In addition, experimental measurements show that under the two-mode propagation conditions of the optical fiber (of about 850 nm single wavelength) having the refractive index profile of FIG.                 

The difference Δτ of propagation delay of the two modes LP ₀₁ and LP ₁₁ is about 0.8 ns / Km;

The attenuation due to the calculated macro bending for the fiber wound once around the major axis with a 40 mm diameter is about 0.28 dB for mode LP ₁₁ and ignored for mode LP ₀₁ ;

It was found that the attenuation due to the calculated macro bending for the fiber wound once around the main axis with a 32 mm diameter was about 0.42 dB for mode LP _{11 and} was ignored for mode LP ₀₁ .

On the other hand, for the single mode propagation conditions (of single wavelength of about 1310 and 1550 nm), experimental measurements showed that the optical fiber having the refractive index profile of FIG. 10 has the characteristics summarized in Table 7.

At 1310 nm At 1550 nm Color dispersion (ps / (nm × Km)) -3.6 13.2 Chromatic Dispersion Slope (ps / (nm ² × Km)) 0.089 0.055 Mode field diameter (㎛) 8.7 10.1 Macro bending (dB) after 100 rotations with a diameter of 60㎜ <10 ^-3 0.2 Macro bending (dB) after one rotation with 40mm diameter <10 ^-3 0.15 Macro bending (dB) after one rotation with a diameter of 32 mm <10 ^-3 0.37 Micro Bending (dB / Km) (g / mm) 0.9 7.5 Attenuation (dB / Km) 0.38 0.199

It can be noted from Table 7 that the macrobending value measured after 100 turns of fiber wound on a 60 mm diameter spindle is less than 0.5 dB.

It can also be noted from Table 7 that an optical fiber having the refractive index profile of FIG. 10 has a color dispersion and chromatic dispersion slope that are equivalent to or better than that of an optical fiber according to the ITU-T G652 standard.

Moreover, the MFD and effective area values are for example to produce low junction loss, connection loss and coupling loss.

Thus, the optical fiber of the present invention operates at about 850 nm and enables to implement a signal distribution network with low cost optoelectronic components (light sources and detectors) in an effective manner and is effective for single mode propagation regions at about 1300 nm and / or 1550 nm. Can be upgraded to work in a way.

Experimental measurements were carried out on a cable approximately 60 m long with an optical fiber having an exponential profile in FIG.

The experimental test showed that the optical fiber had a total of 0.2 dB attenuation at 1550 nm.

In addition, experimental measurements were taken and carried out to measure the attenuation of the optical fiber with the exponential profile of FIG. The experimental test showed that the attenuation values at 1310 nm and 1550 nm matched the values provided by the ITU-T standard.

As a beta profile, there is a small dip in the center of the core 14 (typical of the OVD production process), and a real refractive index profile (such as the refractive index profile of FIG. 10) with a central and outer tail having a pattern similar to a super Gaussian. For, Applicants found that the parameters g, V, a and Δn ₀ can be determined according to the steps disclosed below:

a) filtering the actual profile measured by a measuring noise with, for example, a low pass filter (number) or a moving average method;

b) In general, it can be determined by the radius corresponding to the maximum value taken by the profile (Δn _max ), which determines the radius r _dip generally in the range between about 0.3 μm and 2.5 μm, which defines the maximum extension of the small dip. Making;

c) determining a radius r _max , corresponding to the measurable minimum value Δn of the profile according to the sensitivity of the device, generally Δn = 0.0001;

의 군(群)을 이용한 r_딥 및 r_최대 사이에 측정된 프로파일의 선정법(best fit method)에 따르고 슈퍼가우시안과 측정된 프로파일 사이의 편차를 최소화하는 3가지 파라미터의 값을 결정하게 하는 보간을 수행하는 단계: 그리고d) Super Gaussian function when the parameters Δn ₀ , a, g change

Follow the best fit method of the measured profile between the r _dip and r _max using the group of s and determine the values of the three parameters that minimize the deviation between the super Gaussian and the measured profile. Steps to perform: And

계산단계.e)

Calculation step.

For example, by applying this method to the actual exponential profile of FIG. 10, the following values for g, V, a and Δn ₀ were obtained:

g = 3.85

a = 3.27 μm                 

Δn ₀ = 5.62 × 10 ^-3

V = 3.09.

It can be noted from FIG. 13 that the point (V = 3.09; g = 3.85) is in the region made by line 502.

The method can also be used for the actual refractive index profile in beta form without a small dip. In this case, step b) must be omitted and step d) must be performed on the profile measured between r = 0 and r _max .

The optical fiber 10 of the present invention is formed for use in a signal distribution network for distributing signals to multiple user equipment.

3 shows the invention of a network 100 for resolving signals to a plurality of user electronics 42 having a distribution device 40 and a plurality of optical cables 1 and a plurality of optoelectronic converters 62. An embodiment according to this is shown.

For simplicity of illustration, three optical cables 62 and three user electronics are shown in the embodiment of FIG. 3.

The optical cable 1 allows the distribution device 40 to communicate with user electronic equipment 42.

More specifically, the optical cable 1 is connected to three optical input / output ports of the distribution device 40 for transmitting the optical signal from the distribution device to the optoelectronic converter 62. The optoelectronic converter 62 has a conventional (not shown) photodetector for converting optical signals from the distribution device 40 into corresponding electrical signals and sending these electrical signals to the corresponding user electronics 42. do.

In general, the optoelectronic converter 62 is also provided from a photodetector according to physical requirements and protocols required by the user equipment 42, e.g., the Internet protocol, or typical protocols for digital or analog television signals or telephone signals. With a device intended to form an electrical signal at the output.

Moreover, the optical cable 1 has at least one optical fiber 10 according to the invention.

One of the two ends of the optical fiber 10 is coupled to the optical port of the photodetector of the optoelectronic converter 62, while the other end is coupled to one of the optical ports 43 of the distribution device 40.

According to a variant, the optical cable 1 is advantageously bidirectional, allowing the propagation of signals from the user electronics 42 to the distribution device 40 and from the distribution device 40 to the user equipment 42.

In the bidirectional case, each optoelectronic converter 62 converts the electrical signal from the user equipment 42 into a corresponding optical signal and transmits the optical signal to the distribution device 40 via the optical cable 1. And a photodetector that converts the optical signal from distribution device 40 into a corresponding electrical signal and provides the electrical signal to user electronic equipment 42.

In general, a laser source emits amplitude modulated electromagnetic radiation by modulating the laser supply current or through a conventional amplitude modulator in accordance with information carried by an electrical signal from user equipment 42.

Moreover, in the bidirectional case, each optical cable 1 generally has a first and a second optical fiber 10 according to the invention. The first optical fiber is connected to the laser source of the optoelectronic converter 62 and is formed for transmitting an optical signal from the corresponding user equipment 42 to the distribution device 40. In turn, the second optical fiber is connected to the photodetector of the optoelectronic converter 62 and is formed for transmitting the optical signal from the distribution device 40 to the corresponding user equipment 42.

According to a variant, each optical cable 1 is formed for transmitting optical signals in two directions and is connected to both the laser source and the photodetector of the optoelectronic transducer 62 via a conventional optical coupler or conventional optical circulator. It has a single optical fiber 10 according to the invention.

According to another variant, the optical signal traveling in two directions has different wavelengths, and the coupler is advantageously wavelength selective, for example as in conventional wavelength multiplexing / demultiplexing devices.

In the last variant, two different wavelengths in the two propagation directions of the optical signal, for example, one below the cutoff wavelength for the first higher order mode LP ₁₁ of the optical fiber 10 and the other to operate in a multimode propagation condition. Can be selected above the cutoff wavelength for the first higher order mode LP ₁₁ of the optical fiber 10 to operate in a single mode propagation condition. For example, in the case of optical fiber 10 having the refractive index profiles of FIGS. 1, 2 and 10, the two wavelengths may be about 850 nm and 1310 nm or 1550 nm.

In the case of the multimode propagation condition of the optical fiber 10, the laser source of the optoelectronic converter 62 is, for example, a VCSEL type laser source having an emission at a wavelength of about 850 nm.

In turn, the photodetector of the optoelectronic converter 62 is, for example, a conventional photodiode in the form of a PIN that receives in a dense wavelength band at about 850 nm.

Lasers and photodetectors of this type are available on the market at low cost.

In the case of the single mode propagation condition of the optical fiber 10, the laser source is, for example, a conventional Fabry Perot type laser or a conventional DFB or DBR type that emits in a band of 1300 nm-1350 nm or 1480 nm-1625 nm. Semiconductor laser.

In one example, a power greater than -20 dBm, in particular about -16 dBm, was coupled to the optical fiber 10 to include transmission up to 5 Km at a wavelength of about 850 nm.

In this example, the sensitivity of the photodetector was better than -32 dBm, especially about -34 dBm.

Thus the available light output (output supply) for the optical fiber 10 connection of the above example was greater than 12 dB, in particular about 18 dB.

The photodetector of the laser source and photoelectric converter 62 is generally connected to the optical fiber 10 of the present invention via a conventional optical connector.

The optoelectronic converter 62 is connected to each user electronic device 42 via an electrical cable (not shown), preferably a connector.                 

The electrical cable is a conventional coaxial cable having a conventional UTP-5 type or a corresponding connector, usually terminated with a conventional connector of RJ-45 type.

In addition to the optical fiber 10, the optical cable 1 also includes a plastic coating and an outer plastic sheath to cover the fiber.

In addition, between the plastic coating of the optical fiber 10 and the outer plastic sheath, the optical cable 1 also comprises a reinforcing member such as a plurality of longitudinal yarns made of Kevlar ^™ , for example (not shown). The optical cable is flexible and tensile resistant.

For example, the optical cable 1 is of the type disclosed in EP 0 829 742 filed by the applicant or in the form of a ribbon.

According to a variant, the optical cable 1 also has one or more electrical conductors formed, for example, for carrying a supply current.

Nevertheless, the deformation of the optical cable 1 without electrical conductor is preferred to have the advantage of being inserted into the same wiring conduit used for distributing electrical energy without any electrical safety problems.

In the embodiment of FIG. 4, distribution network 100 is formed to send optical signals (preferably involving digital information) out of optical fiber line 46 to user electronics 42.

In this embodiment, the distribution device 40 is, for example, an optical device including a conventional distributor formed to send optical signals from the optical fiber wire 46 to the three optical input / output ports 43.

In this embodiment, the optical fiber 10 of the three optical cables 1 is preferably secured to the optical port 43 of the distribution device 40 via a fusion joint.

According to a variant, the optical fiber 10 is mechanically connected to the optical port 43 of the distribution device 40 via a conventional optical connector.

In the embodiment of FIG. 5, the distribution network 100 is similar to the distribution network of FIG. 4 except that the distribution device 40 is formed to have optoelectronic equipment 48 and 49.

More specifically, the dispensing apparatus 100 receives, from a plurality of electrical input / output ports 47, a plurality of electrical input signals (preferably in digital form) from the plurality of electrical cables 44; Send the electrical input signal to an electrical processing device 48 that processes the electrical input signal according to the application; Providing a plurality of electrical output signals; Converting the electrical output signal into a corresponding optical signal through an optoelectronic converter (49); The optical signal is provided to the optical input port / output port 43 and is configured to send the optical signal to the optoelectronic converter 62 and thus to the user electronic equipment 42 through transmission on the optical cable 1.

Moreover, the distribution device 40 also receives-via the optical cable 1-the optical signal from the user equipment 42 from the optical port 43; Converting the optical signal into a corresponding electrical signal through an optoelectronic converter (49); Depending on the application, it is configured to send the electrical signal to an electrical processing device 48 that processes the electrical signal to provide a plurality of electrical output signals to the plurality of electrical input / output ports 47.

Electrical processor 48 demodulates, for example, an electrical digital signal from input / output port 47, amplifies the electrical digital signal and optionally modulates the electrical digital signal in accordance with a conventional modulation format. And the signal is selected to be sent to each optical cable 1. Further, for example, demodulating the electrical digital signal from the optoelectronic converter 49, amplifying the electrical digital signal and optionally modulating the electrical digital signal according to a conventional modulation format, and wherein the signal is input to each input. It is configured to be selected to be sent to the port / output port 47.

In general, the optoelectronic converter 49 emits electromagnetic radiation whose amplitude is modulated by modulating a laser supply current or through a conventional amplitude modulator according to information carried by an electrical signal at the output from the processing device 48. A laser source is provided.

Also, in both directions, the optoelectronic conversion device is conventionally formed to receive an optical signal from the optical port 43, convert the optical signal into a corresponding electrical signal, and provide the electrical signal to the processing device 48. Photodetectors are also advantageously provided.

In the case of multimode propagation conditions of the optical fiber 10, the laser source of the optoelectronic converter 49 is, for example, a VCSEL type laser source that emits at a wavelength of about 850 nm.

In turn, the photodetector of the optoelectronic converter 49 is, for example, a conventional photodiode of the PIN type which is received in a wavelength band densely located near 850 nm.

Lasers and photodiodes of this type are available on the market at low cost.

In the case of the single mode propagation condition of the optical fiber 10, the laser source is, for example, a conventional laser in the form of Fabry Perot or in the form of DFB or DBR emitting in the band of 1300 nm-1350 nm or 1480 nm-1625 nm. It is a conventional semiconductor laser.

In turn, the photodetectors are, for example, conventional photodiodes in the form of PINs that are received in the wavelength band of 1300 nm-1350 nm or 1480 nm-1625 nm.

The photodetector of the laser source and photoelectric converter 49 is generally connected to the optical fiber 10 of the present invention via a conventional optical connector.

In the embodiment of FIG. 6, the distribution network 100 is of FIG. 5 except that the distribution device 40 also includes an optoelectronic transducer 50 and the input / output port 47 is an optical port instead of an electrical port. Similar to a distribution network.

More specifically, the distribution device 40 receives a plurality of optical signals (preferably accompanying digital information) from the plurality of optical fibers 46 upon input to the plurality of optical input / output ports 47. ; The optical signal is converted into a corresponding electrical signal through the optoelectronic converter 50, and the electrical signal is sent to an electrical processing device 48 that processes the electrical signal and provides a plurality of electrical signals at the time of application. ; Converting the electrical signal into a corresponding optical signal through an optoelectronic converter (49); The optical signal is provided to the optical input port / output port 43 so as to send the optical signal to the user electronic device 42 through transmission on the optical cable 1.

In addition, the distribution device 40 also receives, from the optical port 43, an optical signal from the user equipment 42-via transmission on the optical cable 1; Converting the optical signal into a corresponding electrical signal through an optoelectronic converter (49); Send the electrical signal to an electrical processor (48) for processing electrical signals; Providing a plurality of digital electrical signals to the optoelectronic converter 50 for converting the plurality of digital electrical signals into corresponding optical signals; The optical signal is provided to an input port / output port 47 and is configured to send the optical signal along a plurality of optical fibers 46.

FIG. 7 illustrates the embodiment of FIG. 6 where the network 100 is a signal distribution network for distributing digital signals to multiple users in accordance with the Fastethernet ^™ 100 Mbit / s protocol. The signal arrives in optical form from the optical input fiber 51 to the optical port 47 and is converted by the optoelectronic converter 50 into a corresponding electrical signal. The electrical signal is processed by the processing device 48, which selects the intended digital signal for each user (e.g., a digital signal according to the EthernetTM 10 Mbit / s protocol) and the digital It is configured to send a signal to the corresponding optoelectronic converter 49. The converter converts the intended digital electrical signal for the user into a corresponding optical signal and sends the optical signal to the user's electronic equipment 42 via the associated optical cable 1.

In addition, in the variant of FIG. 7, each user electronic device 42 is formed to transmit a digital signal according to the Ethernet 10 Mbit / s protocol to the distribution device 40. In one of the optical ports 43, each digital signal from the optical cable 1 is converted into a corresponding electrical signal by an associated optoelectronic converter 49 and sent to the device 48, which sends the electrical signal according to the application. Process. Among others, the device 48 time multiplexes the signal from the other user equipment 42 and into one photomultiplexed electrical signal with the optoelectronic converter 50 according to the Fast Ethernet 100 Mbit / s protocol. To provide. The converter 50 converts the multiplexed electrical signal into a corresponding optical signal and sends the optical signal to an optical port 47 connected to the optical output fiber 52.

In the example of FIG. 7, the processing device 48 is, for example, a ROUTER CATALYST 2900 XL produced by CISCO SYSTEM.

In the embodiment of FIG. 12, the distribution network 100 is also configured in addition to the building or local network consisting of a plurality of optical cables 1 extending between the distribution network 40 and the home networks 601, 603. It is similar to the distribution network of FIG. 6 except it includes an input port / output port 47 and home (or home) networks 601 and 603.

More specifically, the distribution device 40 includes a plurality of optical signals (preferably digital information) from a plurality of optical fibers 46, 46 'and a plurality of electrical signals (preferably also from a plurality of electrical cables 44). Digital) is input to a plurality of input ports / output ports 47 at the time of input.

The signals transmitted by the other electrical cables 44 and the optical fibers 46, 46 'are, for example, signals from other suppliers, such as telephones, televisions and Internet service providers.

The optical signal from the optical fiber 46 is converted into a corresponding electrical signal by the photoelectric converter 50 and sent to the electrical processor 48. The electroprocessing device processes the electrical signals from the optoelectronic transformer 50 and the electrical signals from the electrical cable 44 according to the application, and a plurality of electrical signals are each opto-electronic combiner 49. To provide.

More specifically, the electroprocessing device 48 is sometimes intended for a user associated with the electrical device and provides each optoelectronic synthesizer 49 with electrical signals from various supplies.

In turn, each optoelectronic synthesizer 49 has a different wavelength (typically for each supply or type of service) upon inputting the electrical signal from the various supplies (via the optoelectronic converter 49 ') to the synthesizer. Converts the optical signal into a corresponding optical signal, multiplexes the optical signal to the combiner 41 by wavelength through conventional wavelength selection, etc., and provides a wavelength division multiplexed (or WDM) optical signal to the input / output optical port 43 The optical signal is configured to be sent to a related user through transmission on the optical fiber 10 of the optical cable 1.

In turn, the optical signal from the optical fiber 46 'having a predetermined wavelength (different from the wavelength associated with other supplies or services in the distribution network) is separated at the output by the conventional optical combiner 38 and transmitted to the combiner 41. Directly sent, the combiner multiplexes the optical signal with other signals of different wavelengths.

Although a single optical fiber 46 'and a single optical coupler 38 are shown in FIG. 12, the network has many optical couplers 38 for connecting to multiple corresponding optical fibers 46' linked to other supplies or services. It may be provided.

On output from each optoelectronic synthesizer 49, a WDM signal is sent via the optical cable 1 to the corresponding home networks 601, 603.

The home network 601 is molded and formed with a coupler 39, a plurality of optical cables 1 and a plurality of optoelectronic converters, for example, connected to a plurality of electrical user equipment 42 provided in various rooms of the user's home. 62 is provided. For example, the user equipment 42 may be a telephone, a television receiver and / or a personal computer.

According to an embodiment, the combiner 39 is a conventional optical beam splitter that distributes the optical power of the input WDM optical signal between the outputs connected to the optical cable 1 associated with the various user equipments 42. beam splitter). Moreover, each optoelectronic converter 62-in addition to including a conventional photodetector and optionally a light source, in the case of bidirectional propagation-is also linked from the WDM optical signal to the user equipment corresponding to the converter. And an optical filter formed to extract wavelengths carrying the collected information and to send the wavelengths to the photodetectors. Such filters may be fixed or adjusted automatically or manually, for example, through mechanical, thermal or electrical control. The use of adjustable filters allows the placement of generic modules for optoelectronic converters 62, which can sometimes be used at desired wavelengths. The module also includes an electronic circuit for signal protocol conversion, according to the protocol of the user equipment 42.

According to a variant, the combiner 39 demultiplexes the incoming input WDM optical signal into multiple optical signals of different wavelengths and sends the optical signal to the optical cable 1 associated with several user equipments 42. It is a wavelength demultiplexer. In this case, the preselected wavelength reaches each photoelectric converter 62, and the presence of the optical filter is no longer necessary.

The home network 603 is bus type. Is completely similar to the home network 601 except that the WDM signal arriving from the optical cable 1 connected to the network 603 is sent to the optical signal converter 62; The optoelectronic converter 62 processes the WDM signal and sends the WDM signal to the optoelectronic converter 63. In turn, the optoelectronic converter 63 processes the WDM signal and converts the WDM signal into an optical signal converter. 64).

More specifically, each optoelectronic converter 62, 63, 64 extracts a wavelength from an input WDM optical signal carrying information associated with user equipment corresponding to the converter and sends the wavelength to the photodetector. Has a filter of the type disclosed.

In a variant, each optoelectronic converter 62, 63, 64 derives an output portion from an input WDM optical signal, extracts a desired wavelength from the output portion and sends the remaining output portion of the WDM optical signal to a connected optoelectronic transducer. It is formed to. According to another variant, each optoelectronic converter 62, 63, 64 is formed to extract the desired wavelength directly from the input optical signal, thereby sending a WDM optical signal having the remaining wavelength to the connected optoelectronic converter.

First, if the band requirement is not large, WDM transmission on the optical fiber 10 of the optical cable 1 can be advantageously performed in the multimode propagation region at about 850 nm. For example, the wavelength of the multiple wavelength multiplexed optical signal may be selected in a band configured between 820 nm and 870 nm with an interval of 20 nm, 10 nm, 5 nm or 2 nm.

Then, if the band requirement becomes larger, the WDM transmission can be performed in the single mode propagation region of the optical fiber 10 and the wavelength of the multiple wavelength multiplexed optical signal is, for example, 20 nm, 10 nm, 5 nm or 2 It may be selected from the band having a spacing of nm and configured between 1300 nm-1350 nm and / or 1480 nm-1625 nm.

Further, WDM transmission can be performed in both the multimode propagation region and the single mode propagation region of the optical fiber 10.

For the transmission on the optical fiber 10 from the user side of the distribution network of FIG. 12 to the distribution device 40 side, it can be carried out via a WDM transmission in a manner very similar to the above-described WDM transmission for transmission from the distribution device side to the user side. have. Nevertheless, since the amount of information transmitted from the user side to the distribution device 40 side is limited (generally, adapted to control and / or select received information), the optical fiber 10 from the user side to the distribution device 40 side. The transmission of the phases is preferably performed in accordance with conventional low cost time division multiple (or TDM) transmission. In this case, the distribution network also includes, at each user side, conventional TDM transmission management electronics.

From distribution device 40 to user equipment 42, it is desirable to use one or more available wavelengths for the transmission of service channels for processing failures and / or alert conditions and / or allowing synchronization of TDM transmissions in the opposite direction. It is possible. The service channel is operated in the distribution device 40 via appropriate control electronics and electro-optical converters, and distributed to each optoelectronic converter 62 through output distribution.

In general, the signal distribution network 100 of the present invention includes a plurality of televisions and / or telephones and / or from long distance satellite and / or coaxial cables and / or fiber optics and / or aerial transmissions to a plurality of electronic user equipment 42. It can be used to distribute internet digital signals.

It can also be used, for example, in a LAN distribution network.

8 shows a distribution network 100 of the present invention installed in a building. More specifically, the distribution device 40 is arranged in the basement or basement floor 45 of the building, and the optical cable 1 housed in a suitable wiring conduit of the building, optionally via a home optical network of the type disclosed with reference to FIG. The distribution device 40 is connected to the user equipment 42 located on the various floors of the building.

Included in the Detailed Description of the Invention.

Claims (41)

Distribution device 40, The distribution device 40 has a plurality of optical cables 1 configured to communicate with a plurality of user equipments 42, each of which is due to the core 14, the cladding 12 and the production process. Optical fibers with a predetermined refractive index profile Δn (r) defined by a single radial segment, small dips or diffusion tails, which are independent of possible variations. 10), wherein Δn (r) means the refractive index difference between the core 14 and the cladding 12 as a function of radial distance r, wherein each optical fiber 10 is greater than 1260 nm. As a signal distribution network 100 for distributing signals to a plurality of user equipments 42 configured to provide single mode propagation at large wavelengths and multimode propagation at 850 nm, The refractive index profile Δn (r) of each optical fiber 10 has a macro-bending loss of less than about 0.5 dB at a wavelength of 1550 nm after 100 rotations on a major axis having a diameter of 60 mm, And a signal distribution network for distributing signals to the plurality of user equipments 42, characterized by providing an intermodal delay Δτ of less than about 1 ns / Km at a wavelength of 850 nm. The method of claim 1, And a signal distribution network for distributing signals to a plurality of user equipments whose intermode delay Δτ is less than 0.5 ns / Km at a wavelength of about 850 nm. The method of claim 2, And a signal distribution network for distributing signals to a plurality of user equipments whose intermode delay Δτ is less than 0.05 ns / Km at a wavelength of about 850 nm. The method of claim 1, And a signal distribution network for distributing the signal to a plurality of user equipments having a macro bending loss at a wavelength of 1550 nm after 100 rotations on the 60 mm diameter main axis. The method of claim 1, The optical fiber for distributing signals to a plurality of user equipments having a micro-bending loss of less than about 15 [(dB / Km) / (g / mm)] at a wavelength of 1550 nm. The method of claim 5, The optical fiber for distributing signals to a plurality of user equipments having a microbending loss of less than about 10 [(dB / Km) / (g / mm)] at a wavelength of 1550 nm. The method of claim 1, Wherein each optical fiber has a normalized frequency value (V) comprised between about 3.0 and 3.6 at a wavelength of 850 nm. The method of claim 7, wherein Wherein each optical fiber has a normalized frequency value (V) comprised between about 3.2 and 3.6 at a wavelength of 850 nm. The method according to claim 7 or 8, The optical fiber is a signal distribution network for distributing signals to a plurality of user equipment fabricated by an " external vapor deposition (OVD) " method. The method according to claim 7 or 8, The optical fiber is a signal distribution network for distributing signals to a plurality of user equipment manufactured by a "vacuum vapor deposition" method. The method of claim 1, Wherein each optical fiber has a Δn ₀ value that is a maximum refractive index difference between the core and the cladding comprised between about 5 × 10 ⁻³ to 7 × 10 ⁻³ . The method of claim 1, And a semi-area corresponding to the refractive index profile is between about 0.017 μm and 0.021 μm. The method of claim 12, And a semi-region corresponding to the index of refraction profile is between about 0.018 microns and 0.021 microns. The method of claim 1, And a signal distribution network for distributing signals to a plurality of user equipments wherein the core radius of each optical fiber is comprised between about 3 μm and 6 μm. The method of claim 1, Wherein each optical fiber outside the cladding is for distributing signals to a plurality of user equipments having an external protective coating made of a polymeric material. The method of claim 15, A portion of the outer coating in contact with the cladding having a refractive index greater than the refractive index of the cladding in a temperature range comprised between about 10 ° C. and 60 ° C. The method of claim 15, The external protective coating is a signal distribution network for distributing signals to a plurality of user equipment consisting of a material capable of strongly absorbing electromagnetic radiation. The method of claim 1, Wherein each optical cable also distributes signals to a plurality of user equipments having a second optical fiber. The method of claim 1, And a signal distribution network for distributing signals to a plurality of user equipments further comprising a plurality of optoelectronic converters in communication with the plurality of optical cables. The method of claim 19, A signal distribution network for distributing signals to a plurality of user equipment, each optoelectronic converter having a photodetector. The method of claim 19 or 20, Wherein each optoelectronic converter is for distributing signals to a plurality of user equipment having an optical source. The method of claim 21, And the light source is configured to distribute the signal to a plurality of user equipments configured to operate at a wavelength comprised between about 820 nm and 870 nm. The method of claim 22, And the light source is configured to distribute the signal to a plurality of user equipments configured to operate at a wavelength comprised between about 830 nm and 860 nm. delete The method of claim 21, And at least some of the light sources of the optoelectronic converter are configured to distribute signals to a plurality of user equipments configured to operate at wavelengths comprised between about 1300 nm and 1625 nm. The method of claim 1, And wherein the distribution device is configured to multiplex a plurality of signals of different wavelengths into a single WDM signal and to distribute the signal to a plurality of user equipments to send the WDM signal along at least one of the optical cables. The method of claim 1, A signal distribution network for distributing signals to a plurality of user equipment-on the user side-at least one domestic network connected to a corresponding optical cable and configured to send signals from the optical cable to the plurality of user equipment . The method of claim 27, The home network is a signal distribution network for distributing signals to a plurality of user equipments of star type. The method of claim 27, The home network is a signal distribution network for distributing signals to a plurality of user equipments of a bus type. The method of claim 26 or 27, The home network is a signal distribution network for distributing signals to a plurality of user equipments having a wavelength selective optical coupler configured to wavelength demultiplex the WDM optical signal entering the input. The method of claim 26 or 27, The home network is a signal distribution network for distributing signals to a plurality of user equipments having an optical coupler configured to distribute the output of the WDM optical signal entering the input. The method of claim 1, Each optical fiber 10 is for distributing a signal to a plurality of user equipments having a color dispersion value of one or less of 20, 19, 18, 17 and 16 ps / (nm × Km) at a wavelength of 1550 nm. Signal distribution network. The method of claim 1, Each optical fiber (10) for distributing signals to a plurality of user equipment having a chromatic dispersion value of 15.4 ps / (nm × Km) or less at a wavelength of 1550 nm. Preset refractive index defined by a single radial segment, small dips or diffusion tails separate from the possible variation due to core 14, cladding 12 and production process Profile Δn (r), wherein Δn (r) means the refractive index difference between the core 14 and the cladding 12 as a function of radial distance r, at wavelengths greater than about 1260 nm An optical fiber 10 formed to provide single mode propagation for multimode propagation at a wavelength of about 850 nm, The predetermined refractive index profile Δn (r) has a macro bending loss of less than about 0.5 dB at a wavelength of 1550 nm after 100 rotations on a major axis having a diameter of 60 mm, And provide an intermode delay Δτ of less than about 1 ns / Km at a wavelength of 850 nm. The method of claim 34, wherein An optical fiber having a chromatic dispersion value of one or lower of 20, 19, 18, 17 and 16 ps / (nm × Km) at a wavelength of 1550 nm. The method of claim 34, wherein An optical fiber having a color dispersion value of 15.4 ps / (nm × Km) or less at a wavelength of 1550 nm. 38. An optical cable formed for use in a signal distribution network having at least one optical fiber according to any of claims 34 to 36. delete delete delete delete

Images