KR19990028560A - Fiber Optic Manufacturing Method - Google Patents

Abstract

Optical fibers having optical properties that vary regularly along the length are produced by inserting a plurality of cylindrical plates into a coated glass tube and applying the tube with coated glass particles. Each plate comprises a core region, which optionally includes a coating glass layer. Neighboring plates can form optical fiber portions having different optical properties. Prior to bonding the glass particles, chlorine flows through the tube onto the plate. When the tube starts to sinter, the flow of chlorine is stopped and the sintered particles produce an inwardly directed force, causing the tubes to collide inward onto the plates that are simultaneously melted against each other. The final draw margin can be drawn into a low loss fiber. This method is particularly useful for producing single mode optical fibers with controlled spectroscopy.

Description

Fiber manufacturing method

The present invention relates to a method for manufacturing an optical fiber having optical properties that change regularly over the entire length. In particular, this method is useful for producing spectroscopically controlled (DM) single-mode optical waveguide fibers. Potentially the high bandwidth of single-mode fiber can be realized only when the shape of the system is utilized to the fullest so that the entire spectrum at operating wavelength is near zero or nearly zero. The term "spectral" means pulse extension, which is expressed in ps / nm-km. "Spectral multiplication" means the spectral times the length and is expressed in ps / nm.

If the telecommunications network employs multi-channel communication or wavelength division multiplexing, the system may be mixed with four wavelengths, resulting in loss. This loss occurs when the signal wavelength is at or near the zero spectral wavelength of the optical transmission fiber. This involves spectroscopy of the waveguide fibers, which can reduce signal degradation resulting from the nonlinear waveguide effect. A dilemma arises in the form of waveguide fibers to minimize the mixing of the four wavelengths while maintaining the properties required for systems with long spacing between regenerators. That is, since the mixing of the four wavelengths occurs at a low waveguide spectroscopy, i.e., about 0.5 ps / nm-km or less, the waveguide fibers generally operate near zero of the total spectroscopy to eliminate the mixing of the four wavelengths. Should not be. On the other hand, because of the presence of total spectroscopy, signals with wavelengths spaced at zero out of the total spectra of the waveguide are attenuated.

One method proposed to overcome this dilemma is to construct a system that uses waveguide fiber portions, some of which are connected by cables with positive and negative total spectra. If the weighted average length of the spectra is close to zero for all cable segments, the regenerator spacing can be large. In essence, however, the four wavelengths are prevented from mixing because the signal does not pass through the waveguide portion where the spectroscopy is near zero.

The problem with this method is that each connection between the regenerators must be tailored to provide the weighted average required length of the spectroscopy. Maintaining the same cable spectra from the cable machine to the device is an undesirable additional task and causes a failure. Moreover, the need not only to provide adequate spectroscopy but also to provide cables of the appropriate length with such spectroscopy increases manufacturing difficulties and increases system cost. More serious problems arise when considering the need to change the location of the cable.

This problem is described in US patent S.N. Resolved with the optical fiber disclosed in 08 / 584,868. According to Becky's application, each individual fiber has its own managed spectroscopic system. Preselected, the weighted average of the total spectra, i.e. the total spectral multiplication, is formed in each waveguide fiber. Each waveguide fiber may be replaced with another waveguide fiber formed for the system connection. Thus, all cabled waveguide fibers have essentially the same spectral multiplying properties, and there is no need to assign a particular group of cables to a particular part of the system. The power loss resulting from the mixing of the four wavelengths is essentially eliminated or reduced to a predetermined level, while the spectral of the entire link is maintained to a predetermined degree, which may be generally near zero.

According to Bucky's application, the spectra of DM fibers vary between positive and negative ranges along the length of the waveguide. Spectral multiplication of a particular length 1, expressed in ps / nm, is a multiplication of (D ps / nm-km × 1 km). Positive numbers of ps / nm can be offset with negative numbers of the same ps / nm. In general, the spectra related to length 1 _i may vary sequentially along 1 _i . That is, the spectra D _i are within a predetermined spectral range, but may vary sequentially along 1 _i . In order to indicate the effect of 1 _i on the spectral multiplication expressed in ps / nm, the associated constant spectroscopy D _i , which is a generally constant, consists of the upper part d1 _i . The total of the multiplication (d1 _i × D _i ) then represents the characteristic of the spectral multiplication contribution of 1 _i . It should be noted that at the limit of d1 _i approaching zero, the sum of the multiplications d1 _i × D _i is simply the integral of (d1 _i × D _i ) over the length 1 _i . If the spectral is largely a constant on the additional length 1 _i , the sum of the multiplications is simply 1 _i × D _i .

Spectroscopy of the entire waveguide fiber length is managed by controlling the spectra D _i of each portion d1 _i , so that the sum of the multiplications d1 _i × D _i is over a predetermined wavelength range over which the signal can be multiplexed. It is equal to the numerical value. For advanced systems with long regenerator intervals, the above wavelength range in low attenuation windows ranging from 1525 nm to 1565 nm can be advantageously selected. In this case, the sum of the spectral multiplications for the DM fibers would have to be targeted to zero over the range of wavelengths. In general, the size of (D _i ) is kept above 0.5 ps / nm-km and below 20 ps / nm-km in order to prevent the mixing of the four wavelengths so that too large fluctuations in the waveguide fiber parameters are not required.

The total spectroscopy given above is generally at least 0.1 km long. This low length limit reduces power loss and simplifies the manufacturing process (see FIG. 5).

The period of the DM single mode waveguide is any of a first length having a full spectrum in the first range, a second length having a spectrum in the second range, and a transition length in which the spectrum is switched between the first and second ranges. Is determined by the sum, and the first and second ranges are opposite signals. In order to mix the four wavelengths and prevent any associated power loss on the transition length, it is advantageous to keep the transition length related to the overall spectroscopy as short as possible, below about 0.5 ps / nm-km.

If the transition region between the high and low spectral regions is too long, the center of the transition region will be close to zero with respect to the predetermined finite length of the fiber. This will cause a slight power loss since the four wavelengths are mixed. The longer the switching area, the larger the power loss. Thus, the transition zone must be sharp enough so that the fiber power loss does not result in a total system reduction exceeding the allotted power loss budget.

The main point in the process of producing DM fibers is to be able to form short transition areas. Moreover, the process of making DM fibers should not include the excess loss itself, which is independent of the mixing of the four wavelengths. In addition, the process should be simple and flexible enough to allow for transition to various fiber forms and materials. Thus, the DM fiber must be a single fiber formed by withdrawing a withdrawal preform or withdrawal raw article comprising portions forming fiber sections of different spectra. This single fiber does not contain icing that causes additional loss between the separated and drawn fiber parts. Ideally, the overall attenuation of a single fiber is no greater than the synthesis of the weighted attenuations of each part arranged in series making up it.

Attempts have been made to form DM fiber core rods by melting core rod portions by lathe and welding methods. In addition to the difficulty of forming, the method suffers from a poor installation of the core and causes a problem that the flame causes the core to wet.

Summary of the Invention

It is therefore an object of the present invention to provide an optical fiber having strictly different optical properties over its entire length and an improved method of manufacturing such an optical fiber. It is another object of the present invention to provide a method for producing an optical fiber of the above-described type with a very short switching length between parts having different characteristics. It is still another object of the present invention to provide an optical fiber of the type described above with low attenuation for use as a long distance transmission fiber. It is yet another object of the present invention to provide a method for producing a low loss single mode DM optical fiber having a short switching length. Another object is to provide a method for manufacturing an optical fiber exhibiting low polarization mode spectroscopy.

One aspect of the invention relates to a method of making an optical fiber preform. In summary, the method consists of the following steps. A coating glass particle film is formed in the outer surface of a coating glass tube, and several flat plate is inserted in the said coating glass tube. The optical properties of at least one flat plate in the glass tube differ from those of neighboring flat plates, each flat plate having at least a central region of the core glass. On the other hand, the applied assembly is heated to below the sintering temperature of the coated glass particles, and the centerline gas flows through the tube. The centerline gas is selected from the group consisting of pure chlorine or chlorine mixed with diluent gas. Thus, the applied assembly is heated to sinter the coating, thus generating a radially inward force that melts the tube into the plate, and contracts the coated glass tube in the longitudinal direction and thus forces the neighboring flats against each other. And melt.

Another feature of the invention relates to a single optical fiber produced by the above method. The fiber consists of a plurality of optical fiber parts arranged in series, each fiber part having a glass core and an outer coating made of glass. The first fiber portion is different from each other core neighboring it. The coating of the first fiber portion is the same as the coating of the neighboring fiber portion. Between each optical fiber, two neighboring fiber portions are transition areas, and the length thereof is 10 m or less.

1 is a diagram showing total spectroscopy varying along a waveguide fiber length,

FIG. 2 is a diagram showing how the zero spectroscopy of the waveguide fibers varies to maintain the overall spectroscopy of the waveguide within a preselected range of predetermined wavelength indices,

FIG. 3A is a plot of input power versus power loss for a system consisting of partial lengths of certain waveguides with low overall spectroscopic quantities,

FIG. 3B is a plot of input power versus power loss for a system consisting of a partial length of a particular waveguide with a high total spectroscopic amount,

4 is a view showing the total power loss versus the spectrum,

5 is a diagram showing the length of the power loss band spectral change period,

6 is a view showing the power loss to switching area length,

7 is a schematic diagram illustrating an optical fiber manufacturing process in which neighboring portions have distinctly different characteristics,

8 is an enlarged view illustrating a cross section of the flat plate of FIG. 7;

9 shows the application of a layer of applied glass particles to a tube,

FIG. 10 is a cross-sectional view of the molten assembly produced by the bonding / melting step shown in FIG. 7,

11 is a partial cross-sectional view showing a change to the embodiment of FIG. 7,

12 to 13 are diagrams showing the refractive index of the modified spectroscopic optical fiber.

Spectroscopically Managed Fiber Forms

The overall spectroscopy of the DM fibers is shown in a table compared to the waveguide length in FIG. 1. Total spectroscopy is shown alternately between positive (2) and negative (4). On the other hand, Fig. 1 shows a plurality of partial lengths representing negative spectra and a plurality of partial lengths representing positive spectroscopy, and only one negative spectral partial length and one positive spectral partial length are required. The extension in the total spectral values indicated by line 6 indicates that the total spectral changes with the wavelength of propagated light. The horizontal line of the extension 6 represents the total spectroscopy for a particular light wavelength. In general, the length of the waveguide 8 characterized by the particular total spectroscopy is at least about 0.1 km. There is essentially no upper limit on the length 8 except that the sum of the multiplications, i.e., the length X corresponding to the entire spectral can be judged as a necessity to match the preselected value.

The plot of wavelength versus total spectroscopy shown in FIG. 2 helps to illustrate the importance of designing for DM single mode waveguide fibers. Lines 10, 12, 14 and 16 represent the total spectra for the four individual waveguide fibers. Above the narrow wavelength range taking into account each waveguide, i.e., about 30 nm, the spectra will be nearly straight, as shown. The wavelength range in which multiplexing is performed is in the range of (26) to (28). All waveguide portions having a zero spectral wavelength between the ranges (18) to (20) are combined with waveguide portions having a zero spectral wavelength between the ranges (22) to (24) above the operating windows (26) to (28). Calculate a waveguide with a preselected total spectroscopy.

The following example is based on FIG. 2. Assume the operating window is 1540 nm to 1565 nm. Assume that the single mode waveguide fiber has a spectral gradient of about 0.08 ps / nm-km. Line 30 is 0.5 ps / nm-km and line 32 is 4 ps / nm-km. The whole spectroscopy within the operating window is subject to the condition that it should be in the range of about 0.5 to 4 ps / nm-km. A simple straight line calculation yields a zero spectral wavelength range 18-20 of 1515 nm to 1534 nm. Similar calculations yield zero spectral wavelength ranges 22 to 24 of 1570 nm to 1590 nm. The algebraic addition of the total spectroscopy of the waveguide fiber with zero spectroscopy within the above-described range yields a total spectroscopy of 0.5 to 4 ps / nm-km.

The shape of the DM fiber is strongly dependent on the details of the telecommunication system seen in FIGS. 3A and 3B showing the input power band power loss for a 120 km link with eight channels, the frequency division of which is 200 GHz. . In this case, the power loss is mainly due to the mixing of four wavelengths. Curve 62 in FIG. 3A rises steeply with a power loss of approximately 1 dB for an input power of about 10 dBm. For an input power of 10 dBm, the loss is about 0.6 dB (curve 64). The total spectral amount for all curves is about 0.5 ps / nm-km. However, for the steeper curve 62 the partial length for the entire spectral of a given signal is 10 km. The length of the corresponding part of the spectrum in curve 64 is 60 km. The additional loss is due to further conversion through zero spectroscopy for the shorter 10 km partial length case. Another term for the 10 km case is the path segmentation of the signal proportional to the length of the partial oscillation and is generally not large enough to prevent the four wavelengths from mixing. "Vibration portion length" is the positive or negative spectral portion length for a predetermined period of time. In parts where there is no signal associated with the vibrating portion length, the positive and negative vibrating portion lengths are considered equal.

However, the total spectral amount affects the power loss because it affects the path splitting. Curve 66 in FIG. 3B shows power loss for the same system as shown in FIG. 3A except that the partial length is short at about 1 km and the total spectral amount is 1.5 ps / nm-km. Making the waveguide total spectra from wide positive amplitude to negative amplitude significantly reduces power loss from 0.6 dB to 0.2 dB. The loss difference of about 0.4 dB / 120 km is large enough as the difference between the functional and non-functional links, especially for long links that are not reproduced at 500 km or more.

4 is generally described in the same manner as FIGS. 3A and 3B. Curve 68 represents power loss over the entire spectral amount. The partial length of the wavelength is usually about 1 km since the shortest cable used is about 2 km in length. There are also eight channels with a frequency division of 200 GHz, a total length of 120 km and an input power of 10 dBm. In addition, power loss increases rapidly when the total spectral amount falls below 1.5 ps / nm-km.

The system design can be seen from another aspect of FIG. In this case, the spectroscopic amount is fixed at 1.5 ps / nm-km. Curve 70 shows the power loss for the partial length amount for a system with an input power of 10 dBm and 8 channels of frequency division of 200 GHz. The length is selected to be 60 spectroscopic partial lengths and the partial lengths are allowed to vary. If the part length is more than 2 km, low power losses occur. However, at relatively large total spectral amounts, little is gained by extending the partial length beyond 2 km. As can be seen from curve 72, when the number of channels used is reduced to four, generally a low four wavelength mixing loss is compensated.

Another type of conception is the sharp transition length from which the entire spectral changes the signal. Signal path splitting here is also affected by the switching length. Thus, a shallow transition can result in a signal traveling through the waveguide region of nearly zero full spectroscopy, which in turn adversely affects the power loss resulting from mixing four wavelengths.

The following example shows the effect of switching length on power loss. Assume that the input output is 10dBm. Four channels with a frequency division of 200 GHz are used. The total spectral amount is 1.5 ps / nm-km and the length of the vibrating portion of the total spectral is considered to be 2 km. As shown by the curve 74 in FIG. 6, the plot of power loss over the transition length indicates that a short transition length is preferred.

Textile manufacturing

A method of making a very short transition region is shown in FIGS. 7 and 8. To carry out this method, the core preform can be prepared by known processes. Examples of processes that can be employed to make core preforms include: outside vapor deposition (OVD), vapor axis deposition (VAD), limited chemical vapor deposition (MCVD) where core layers are formed inside glass tubes, Plasma Chemical Vapor Deposition (PCVD), a reaction-induced plasma. The core preform may be formed entirely of core glass or may be formed of a core region and an application region.

Two or more cylindrical eb moldings are initially formed which can be formed into an optical fiber bundle with different optical properties and which can be overlaid. For most applications, only two different types of core preforms are required; Two preforms are used in the embodiment shown in FIGS. 7 and 8.

The first and second preforms are inserted into the flat plates 81 and 82, respectively. The length of the plate depends on the particular type of fiber produced. In the production of DM fibers, the length of the flat plates 81 and 82 is determined to yield the desired portion length in the final optical fiber. Plates can be made by a simple score and snap method. The flat plate 81 has a core region 83 and an application region 84; The flat plate 82 has a core region 85 and an application region 86.

The tubular glass handle 92 having an annular projection 97 is melted at one end of the elongated glass tube 90. The handle 92 is part of a gas supply system in the form of a ball joint of the type described in US Pat. No. 5,180,410. The protruding portion 97 is employed to be placed at the base of the groove of the support tube (not shown) for supporting the handle 92 to the coupling furnace. The tube 90 is heated and a recess 98 is formed near the handle 92. Optionally, the portion of the handle 92 adjacent to the tube 90 may be concave. An assembly comprising a handle 97 and a tube 90 is inserted into a shelf (not shown) and rotated against the burner 100 which deposits coated glass particles or flexible layer on the tube 90 ( 9). Coating 91 may be formed with a sufficient outer diameter (OD) through which the final preform may be drawn and combined into an optical fiber having the desired optical properties. Layer 91 may partially overlap over handle 92 as shown in FIG. 7.

The tube 90 begins with one end fixed to the handle 92 lower than the other end, and the flat plates 81 and 82 are alternately inserted into the upper end of the tube 90. The plate cannot fall beyond the recess 98. The tube 90 is heated and the recess 99 is formed in the vicinity of the opposite recess 98. When the tube 90 is reversed, the recess 99 prevents the flat plate from falling out of the recess.

The handle 92 extends from the lower support tube (not shown) to insert the assembly 94 into the engagement muffle 95. While the assembly 94 is heated in the combined furnace, dry gas (arrow 93) flows up through the furnace. Dry gas is usually composed of a mixture of chlorine and an inert gas such as helium. A gas flow containing chlorine (arrow 96) flows from tube 92 to tube 90. Although gas flow 96 may include a diluent such as helium, pure chlorine is suitable for washing. Since the diameter of each plate 81, 82 is slightly smaller than the inner diameter of the tube 90, chlorine flows down around the circumference of each plate; It also flows or spreads between neighboring plates. The chlorine is then discharged through the bottom of the tube 90. Chlorine functions like a high temperature chemical cleaning agent. In this high temperature chlorine washing step, the temperature is below the bonding temperature of the flexible coating 91 so that the gap between the plates 81, 82 and the tube 90 remains sufficiently open for the time required for the washing to begin. . The chlorine washing step is more effective at high temperatures. The temperature of the washing step is preferably at least 1000 ° C., because at low temperatures the duration of the step is too long to be undesirable for commercial purposes. Clearly, lower temperatures may be employed if the process duration is not taken into account. The high temperature chlorine flow between tubes 90 and plates 81 and 82 is very useful in that the flow combines adjacent plates, tubes, and surfaces of the plates without forming bubbles at the contact surfaces. Bubbles contain defects such as air bubbles and impurities that can form attenuation in the final optical fiber.

When the assembly 94 is lowered into the muffle, the walls of that portion of the tube 90 at the end of the flexible layer 91 break and melt together, thus breaking off the chlorine flow in the centerline. As an optional step, a valve can be connected to draw vacuum into the tube. If the assembly 94 continues to move into the muffle, first the tip and the rest of the assembly are affected by the maximum furnace temperature sufficient to sinter the flexible layer 91. The flexible layer 91 shrinks in the radial and longitudinal directions when sintered.

When the flexible layer 91 shrinks in the longitudinal direction, this reduces the tube 90 in length. Since this presses the plates together when neighboring plates 81 and 82 reach the sintering temperature, they melt together without forming bubbles. Without the longitudinal shrinkage of these tubes, neighboring plates cannot be sufficiently melted to form low loss optical fibers.

When the flexible layer 91 shrinks radially, it exerts a radial inward force on the tube 90. This forces the tube 90 inward relative to the plates 81 and 82 to form a melt assembly 98 (see FIG. 10) in which the three regions 81 ′, 90 ′, 91 ′ are completely melted. do. Region 90 'is a collapsed tube and region 91' is a sintered porous coating. Relatively low density pliability provides more inward force; However, the flexible layer must have a sufficient density to prevent cracking.

Reinforcement of the flat tube filled applicator to yield bubble free preforms is an important process step. In order to melt the plates together without bubbles, it is necessary to flow chlorine through the tubes to chemically clean the surface. However, the step of applying a vacuum after the hollow tip is melted is unnecessary.

The melt assembly is removed from the combined furnace. Regions 90 and 91 of melt assembly 98 function like a coating in the final optical fiber. The assembly 98 can be used as a draw gap and can be drawn and drawn directly into the optical fiber. The melt assembly 98 may optionally be provided with additional coating prior to the fiber withdrawal step. For example, a coating of applicability may be laminated onto assembly 98 and then bonded. Optionally, assembly 98 may be inserted into the application glass tube. If additional application is to be added, the diameter of the core area of the plates 81 and 82 should be adjusted accordingly.

Considering melting the plate or core rods before inserting them into the application glass tube, the method is easy to implement, which can be achieved in the dry state. The method is self-aligned in that neighboring core bars having different diameters are centered on the axis of the final withdrawal void when the tube 90 collapses inwards during sintering of the porous glass coating 91.

The method according to the invention creates new degrees of freedom in controlling fiber properties. This forms an optical fiber having a length of neighboring regions or heterogeneous properties. Highly varying transition regions connect neighboring fiber lengths. The attenuation of this fiber is equal to the attenuation of a standard long distance communication fiber of 0.25 dB / km or less, preferably 0.22 dB / km.

In the embodiment shown in FIG. 11, recesses 98 and 99 are not formed inside the tube 90. The short length 104 of the glass capillary is melted at one end of the tube 90, and the glass handle is melted at the opposite end of the tube 90. Plates 81 and 82 are inserted into the tube 90 past the handle. The plate does not fall beyond the tube 104 because the tube has a relatively small diameter. When the assembly is lowered into the combined furnace to begin the sintering process, the tube 104 initially melts to stop urea flow.

DM fiber manufacturing

Fibers with controlled spectroscopy are formed into preforms capable of forming single mode optical fibers having different zero spectral wavelengths. Spectrum of waveguide length can be altered by varying various waveguide measures such as appearance, refractive index, refractive index cross section or configuration. All large refractive index cross sections change the overall spectroscopy because they provide the flexibility required to adjust waveguide spectra. This is described in US Pat. Nos. 4,715,679 to Bhagavatula and in S.N.08 / 323,795, S.N.08 / 287,262, and S.N. It is described in detail in 08 / 378,780.

One form of refractive index cross section useful for forming an optical fiber having zero spectroscopy at a predetermined wavelength is a relative surrounded by a ring-shaped region having a low refractive index alternately surrounded by an outer ring region having a higher refractive index than the outer ring region of a lower refractive index region. This has a central region with a high refractive index. The refractive index cross section of another embodiment (see FIG. 13) comprises a central region having a constant refractive index equal to the applied glass refractive index and a neighboring ring region with essentially increased refractive index. Optical fibers having a refractive index cross section of this type can be easily manufactured.

The simple DM fiber refractive index cross section is a step cross section. Two core preforms may be formed of the same core and the coating material, with the radius of one core area being larger than the other. The withdrawal margin is drawn to fibers having a length of the first core radius interspersed between the lengths of the second core radius larger than the first radius. Core diameter differences ranging from about 5% to 25% are sufficient to cause negative spectroscopic changes at a predetermined amount. In general, a radius change range of 5% to 10% is sufficient for most applications.

The following example describes the formation of a single mode DM fiber suitable to provide zero spectroscopy at 1545-1555 nm. Two different core preforms are formed in a manner similar to that described in US Pat. No. 4,486,212, which is incorporated herein by reference. In summary, the method of the patent comprises the steps of: (a) laminating glass particles on a mandrel to form a porous glass preform; (b) combining the porous preform and removing the mandrel to form a dry and sintered preform; (c) extending the sintered preform and closing the hole in the shaft. All core preforms have a core index cross section of the type shown in FIG. 12. As the first core preform is so, if an application is provided here and drawn with a single mode fiber having an outer diameter of 125 μm, its zero spectroscopy will be 1520 nm. The preform extends from 7 mm to 7.1 mm in diameter. The elongated first and second preforms are cut to line to form plates 81 and 82 of substantially equal length. The flat plate 81 has a core region 83 and an application region 84; The flat plate 82 has a core region 85 and an application region 86.

1 m silica tube is employed; It has an inner diameter of 7.5 mm and an outer diameter of 9 mm. The technique related to FIG. 7 is employed to fill the tubes 90 with flat plates 81 and 82. The coating 91 is molded to an outer diameter sufficient for the final molded article to be joined and drawn out to a single mode fiber of 125 μm outer diameter.

The final assembly 94 floats in the combined furnace. When assembly 94 rotates at 1 rpm, it is lowered into engagement muffle 95 at a rate of 5 mm per minute. A gas mixture (arrow 93) consisting of 50 sccm of chlorine and 40 slpm of helical flows up through the muffle. A centerline flow of 0.3 slpm flows down around the plates 81 and 82 and exits from the bottom of the tube 90. The maximum temperature in the combined furnace is about 1450 ° C. As the assembly 94 moves down into the furnace, the centerline element flow chemically cleans the inner surface of the tube 90 and the surface of the plates 81, 82. As the assembly 94 moves further into the muffle, that area of the tube 90 located below the plate melts to stop centerline element flow. The valve (not shown) is then connected to draw a vacuum into the tube 90. The assembly 94 continues to move into the muffle and the coating 91 is sintered. The tube 90 is forced inward relative to the plates 81 and 82, and the contact surfaces of all the glass elements are melted. When the casting 91 is sintered, the tube 90 becomes shorter, and a bubble-free molten joint is formed between neighboring plates.

After being removed from the bonding furnace, the withdrawal margin formed by this process is withdrawn to form a DM optical fiber having an outer diameter of 125 mu m. The single mode DM optical fiber formed by this process is drawn without being overturned; Attenuation is typically 0.21 dB / km. This is the same attenuation shown by the single mode spectroscopically modified fiber drawn from the preform formed into one of the 7 mm core rods.

Two different types of plates employed in the fiber manufacturing process are combined to provide a zero spectral wavelength of 1545-1555 nm. The zero spectral wavelength is determined by the total length of each type of core in the fiber. The zero spectral wavelength of the fiber can be changed by changing the length ratio of each kind of core in the fiber by cutting off a portion at one end of the fiber.

The vibratory portion length and duration are controlled by the length of the core preform plate. Fibers with vibrating portion lengths of 1.2 to 2.5 km are drawn out.

Different fiber forms

The method according to the invention is described in particular in connection with the production of a DM single mode optical fiber, a description of how to make such a fiber is disclosed in the above detailed embodiments. However, it can be employed to produce other types of optical fibers having optical properties that change regularly along the fiber length. In each example, the fibers can be made by inserting a suitable plate into the tube and processing the tube as described above.

Magnetic Brillouin Dispersion (SBS) can be minimized by providing staggered lengths in fibers that clearly show different amounts of change in Δ, wherein Δ is (n ₁ ² -n ₂ ² ) / 2n ₁ ² (n ₁ And n ₂ are the refractive indices of the core and the coating, respectively). One of the plate shapes used to make the fiber preform shows a given Δ, and the other type of plate shows a very different value of Δ. The Δ value of the fiber core can be adjusted by changing the components of the core and adjusting the amount of impurities in the core, ie by adding other impurities to the core. Numerous impurities, including oxides of tantalum, aluminum, boron, can be employed to change other properties such as refractive index and viscosity.

Fibers providing a filtration function can be produced by alternately laminating a plurality of plates capable of forming an optical fiber having a filtration function in a tube and a plurality of plates capable of forming standard and non-filtering optical fibers.

The plates do not have to be identical or of nearly the same length. For example, the fiber may comprise a relatively short portion, the core of which portion is applied with active impurity ions that can emit stimulated light when light with a suitable wavelength is pumped. Uncommon impurity ions, such as erbium, are particularly suitable for this purpose. Thus, fibers having erbium-coated core portions located at spaced intervals along the length can be made by employing a plate having a relatively long standard plate, an erbium-free core and a relatively short erbium-coated core. .

Fibers having a regularly decreasing size, such as those employed for soliton fibers, can be produced by inserting a plurality of flat plates each having a core diameter smaller than those described above or having a core diameter larger than those described above in the tube. have. Optionally, other core features affecting the spectroscopy can be varied in the plate such that the spectroscopic final fiber decreases monotonically from one end of the fiber to the other.

The above embodiment employs alternatingly stacked flat plates having heterogeneous optical properties. In one embodiment, a single core preform is used to form all plates. The single preform is formed such that the core has a refractive index cross section that is asymmetrically azimuthally. For example, the core may deviate slightly from the circle, ie an ellipse with a cross section of the core having a major axis and a minor axis (see US Pat. No. 5,149,349). Optionally, the fibers may include stress rods on opposite sides of the core as described in US Pat. No. 5,149,349. Elliptical core fibers can be formed as follows. The plate is cut from the preform. An application glass flexible film is provided to an application glass tube. The plate is inserted into the coated glass tube so that the long axis of the elliptical core of one plate rotates about the long axis of the neighboring core. After application casting is combined, the plates are melted in the tube and melted together, and the final draw margin is drawn into the optical fiber with low polarization mode spectroscopy.

Although specific embodiments of the invention have been described in detail, the invention is nevertheless limited only by the following claims.

Claims (30)

Laminating a coated glass particle film on an outer surface of the coated glass tube having first and second ends; The optical properties of one plate in the coated glass tube differ from those of neighboring plates, each plate having a central area of the core glass, and inserting a plurality of plates into the coated glass tube; Heating the applied assembly to below the sintering temperature of the coated glass particles; Flowing a centerline gas selected from the group consisting of pure chlorine and chlorine mixed with diluent gas through the tube; Heat the applied assembly to sinter the coating, generate radially inward force to impinge and melt the tube against the plate, shrink the coated glass tube in the longitudinal direction, and adjacent flat plates are forced and melted against each other. The optical fiber preform manufacturing method, characterized in that consisting of steps to make. 2. A method according to claim 1, wherein each of said plates consists of an application area surrounding said central core glass area. 3. The method of claim 2, wherein the two neighboring plates in the coated glass tube have a core having an elliptical cross section, and the major axes of the cores of the two neighboring plates are not aligned. The method of claim 1, wherein the chlorine-containing gas is composed of pure chlorine. The method of claim 1, wherein the chlorine-containing gas is composed of chlorine and a diluent gas. 2. A method according to claim 1, wherein during the period of impinging the application glass tube onto the plate, the flow of the centerline gas continues until it is shorted by the impact of the softened glass member. 7. The area of the coated glass tube near the second end is deformed inward, and during the period of impinging the coated glass tube onto the plate, the flow of the centerline gas is shorted by the impact of the coated glass tube. Optical fiber preform manufacturing method characterized in that continued until. 7. The extension tube of claim 6, wherein the extension tube is melted at the second end of the application glass tube, and during the period of impinging the application glass tube onto the plate, the flow of the centerline gas continues until it is shorted by the impact of the extension tube. A method for producing an optical fiber preform, characterized in that. The method of claim 1, wherein after the application glass tube impinges on the plate, the source of the centerline gas is shorted in the first and second application glass tubes, and then the vacuum source is connected to the second end of the application glass tube. Optical fiber preform manufacturing method. The method of claim 1, wherein the refractive index cross section of one of the flat plates is different from the refractive index cross section of a neighboring flat plate. The method of claim 1, wherein the core region of the first plate includes impurities capable of amplifying light, and the core region of the plate adjacent to the first plate is free of the impurities. Laminating a coated glass particle film on an outer surface of the coated glass tube having first and second ends; The optical properties of one plate in the coated glass tube differ from those of neighboring plates, each plate having a central area of the core glass, and inserting a plurality of plates into the coated glass tube; Heating the applied assembly to below the sintering temperature of the coated glass particles; Flowing a centerline gas selected from the group consisting of pure chlorine and chlorine mixed with diluent gas through the tube; The applied assembly is heated to sinter the coating, thus generating a radially inward force to impinge and melt the tube against the plate, causing the applied glass tube to shrink longitudinally and thus the neighboring flats to one another. Forcing and melting to form a sintered preform; And manufacturing an optical fiber having a plurality of longitudinal portions each corresponding to the plate from the sintered preform. 13. The optical fiber manufacturing method according to claim 12, wherein the core area of each flat plate in the coated glass tube is different from the remaining core areas of each flat plate. 15. The method of claim 13, wherein when the portion is separated from one end of the fiber to the other end, the optical properties of the plate are such that each portion of the fiber exhibits less spectroscopy than that of the neighboring portion. The optical property of claim 12, wherein the optical properties of the plate are such that each part of the fiber exhibits a value of Δ that is different from the value of Δ of the neighboring part of the fiber, wherein Δ = (n ₁ ² n ₂ ² ) / 2n ₁ ² , and n ₁ and n ₂ are film refractive indexes of the core and the fiber, respectively. 13. The optical characteristic of claim 12, wherein the optical characteristic of the fiber is such that a first portion of the fiber propagates a given wavelength of light and one portion of the fiber neighboring the first portion filters the given wavelength of light. Optical fiber manufacturing method. Providing a plurality of cylindrical first core plates having a central area of the core glass; Providing a plurality of cylindrical second core plates having a radial refractive index of the plurality of second plates different from those of the plurality of first plates and having a central area of the core glass; Laminating a coated glass particle film on an outer surface of the coated glass tube; Alternately inserting a plurality of first and second plates into the coating glass tube; Flowing a centerline gas selected from the group consisting of pure chlorine and chlorine mixed with diluent gas between the tube and the plate, between adjacent plates and from the second end to the first end of the coated glass tube; Heating the tube to a temperature high enough to chemically clean the inner surface of the coated glass tube and the outer surface of each plate; The applied assembly is heated to sinter the coating, thus generating a radially inward force to impinge and melt the tube against the plate, causing the applied glass tube to shrink longitudinally and thus the neighboring flats to one another. Forcing and melting to form a sintered preform; And manufacturing an optical fiber having a plurality of longitudinal portions each corresponding to the plate from the sintered preform. 18. The optical property of claim 17 wherein the optical properties of the plate exhibit a spectral given a portion of the fiber corresponding to the plurality of first plates at a given wavelength of light, and wherein the portion of the fiber corresponding to the plurality of second plates is given a wavelength of light. And a second spectra different from the spectroscopy given in which the spectra of the fiber at the given wavelength are values between the given spectroscopy and the second spectroscopy. A plurality of optical fiber portions arranged in series each having a glass core and a glass outer coating, a core of a first fiber portion different from the core of each fiber portion neighboring the first portion, and a first fiber identical to the coating of the neighboring fiber portion A single optical fiber, characterized in that it consists of a transition zone of 10 m or less in length between the encapsulation of the portion and each of the two neighboring fiber portions. 20. The method of claim 19, wherein the core of each fiber portion exhibits an asymmetrically asymmetric refractive index cross section with a maximum index of refraction, wherein the maximum index of refraction of the first fiber portion is not aligned with the maximum index of refraction of one neighboring fiber portion. Characterized by single optical fiber. 20. The core of claim 19 wherein the core of the first fiber portion and the core of one neighboring fiber portion are oval and the major axis of the elliptical core of the first fiber portion is not aligned with the major axis of the elliptical core of one neighboring fiber portion. Not characterized in that a single optical fiber. 20. The single optical fiber of claim 19, wherein the refractive index of the core of the first fiber portion is different from the refractive index of the core of the neighboring fiber portion. The method of claim 19, wherein the Δ value of the first fiber portion is different from the Δ value of the neighboring fiber portion, and Δ = (n ₁ ² n ₂ ² ) / 2n ₁ ² , where n ₁ is the maximum refractive index of the fiber core. And n ₂ is the refractive index of the fiber coating. 20. The single optical fiber of claim 19, wherein the core component of the first fiber portion is different from the core component of the neighboring fiber portion. 20. The single optical fiber of claim 19, wherein the core of the first fiber portion comprises impurities capable of amplifying light, and the core of the neighboring fiber portions is free of the impurities. 20. The method of claim 19, wherein when the fiber portions are separated from one end of a single fiber to the other end, the optical properties of the fiber portions are such that each fiber portion is spectroscopic below the spectroscopy of neighboring fiber portions. Optical fiber. 20. The single optical fiber of claim 19, wherein the first fiber portion filters a given wavelength of light and the neighboring portion scatters a given wavelength of light. 20. The method of claim 19, wherein the first fiber portion represents a given branch at a given wavelength of light, and the neighboring fiber portion exhibits a second spectrum different from the given spectrum at a given wavelength of light; A single optical fiber, characterized in that it is a value between a given spectroscopy and said second spectroscopy. 20. The single optical fiber of claim 19, wherein the attenuation of the single optical fiber is 0.25 dB / km or less. 20. The single optical fiber of claim 19, wherein the attenuation of the single optical fiber is 0.22 dB / km or less.