MXPA97002461A - Optical fiber switching device for transmission system and mi components - Google Patents

Abstract

A fiber optic device for use in a fiber optic transmission system and components thereof includes a continuous-pass fiber and one or more lengths of circulating fibers connected to the continuous-pass fiber by the respective optical switches to selectively send a signaling to through the circulating lengths of fiber as it propagates along the continuous-pitch fiber. The circulating fiber lengths are either dispersion compensating fibers or fibers impurified with a substance that amplifies or absorbs the signal in the respective presence or absence of a pump signal. The invention therefore allows various amounts of dispersion or gain (absorption) to be selectively connected for use or disuse depending on the needs at the time. For example, an amplifier component that could serve as a pre-amplifier or power device or in line depending on the smaller or greater amount of gain fiber chosen by means of connecting, the device can be interconnected with the transmission system or the components of the same by means of splicing to the ends of the fiber of continuous passage or by means of the optic switches connected to the ends of the fiber of step contin

Description

OPTICAL FIBER SWITCHING DEVICE FOR TRANSMISSION SYSTEM AND COMPONENTS OF THE SAME FIELD OF THE INVENTION This invention relates generally to fiber optic transmission systems and signal amplifier components used therein, and more particularly to a fiber optic device for use in such a system or component thereof that provides selectively variable quantities of effectors of gain, dispersion. or filtration (absorption) of signals in the same or.

BACKGROUND OF THE INVENTION Telecommunication transmission systems using fiber optic technology have outperformed wire-based systems as the industry model for their convenient features. For example, systems that employ fiber optic waveguides are able to provide much higher bandwidth than wire-based systems, are relatively immune to electromagnetic interference, and are more secure than their counterparts. wire base. In addition, components such as fiber optic amplifiers are eclipsing older style repeaters and generators because of their proven advantages. When fiber transmission systems were introduced for the first time, they exhibited bandwidth capabilities that easily met contemporary demands. Current bandwidth demands, however, have increased dramatically and present new challenges over low bandwidth systems such as or dispersion control. As is well known, optical fibers exhibit disp > ersion; that is, the different wavelengths of a signal carried by a fiber propagate at different speeds through the fiber. While the scattering effects in a low bandwidth signal may be relatively insignificant, the scattering of signals may be a limiting factor as the bandwidth of the signal increases. For example, modern fiber optic transmission systems can be provided to transmit data at speeds of more than 2.5 gigabits per second. Dispersion compensation is often necessary for reliable, error-free transmission at data rates exceeding 2.5 gigabits per second. One method to compensate for dispersion in long-path fiber optic transmission systems is to provide a predetermined length of dispersion compensating fiber in the system. If the dispersion characteristics of the section of a transmission system are known, then an adequate length of dispersion compensating fiber can be provided to reduce or eliminate the overall dispersion of the system. Such teaching is set forth in U.S. Patent No. 5,361,234, issued November 1, 1994, which is incorporated herein by reference. As is known, the normal transmission fiber is designed for the minimum attenuation for signals in the penetrable spectrum in 1550 n band transmission, and for the minimum dispersion in the 1300 n band penetrable spectrum. The effects of the dispersion therefore become a decisive point since almost all transmission occurs in the penetrable spectrum of 1550 nm. The new long-path fiber transmission systems can be designed to incorporate the changed fiber in their dispersion to control dispersion at the longer transmission wavelengths. However, millions of kilometers of fiber optic transmission lines have already been installed in which the fiber for dispersion in the penetrable spectrum of 1300 nm is minimized. The transmission signals in the 1550 n band therefore exhibit dispersion in amounts that are large enough to require compensation. In addition, as the data rate of the transmission signals increases from about 2.5 Gbit / s to very high data rates such as 40 Gbit / s, for example, the amount of tolerable dispersion in the system decreases, making the tuning capability of dispersion compensation a convenient feature. Until now, there has not been a convenient method for either compensation in the field of activity for this specific purpose or adjustable tuning in the field of activity of the dispersion in a fiber optic transmission system. Another inherent characteristic of fiber optic transmission systems is the attenuation of signals due to the loss mechanisms in fiber optic waveguides. Indeed, minimizing dispersion and attenuation are two of the main design challenges associated with both new and existing fiber transmission systems. Due to the attenuation of the fiber, signal regenerators in general and fiber optic amplifiers in particular, are integral components of fiber transmission systems. In effect, fiber optic amplifiers are characteristically present either alone or in combination at the beginning and end of the system, respectively, as power and preamplifier, and intermediate thereof as an in-line amplifier. Contemporary fiber amplifiers include a fiber waveguide to which it is impurified with a rare earth element (gain fiber) such as erbium, for example. The gain fiber is pumped by an excitation source having a wavelength smaller than the main wavelength of the communication signal carried by the fiber. Both the pump and the wavelengths of signals propagate along the same fiber path. Additional lengths of gain fiber can be added to the signal transmission path to provide greater amplification of the communication signals. For example, depending on the upstream or downstream components of a fiber amplifier, and its distances from the amplifier, a power amplifier could be used as an in-line amplifier by adding an additional length of fiber to the amplifier. gain to the gain fiber of the power amplifier. Similarly, additional stretches of doped fiber could be added to the system where they could provide a filtering effect on one or more wavelengths in the wavelength band of signals for gain spectrum formation or equalization of gain that is important in the applications of UDM, depending on the existence or reduction of the signal of pumping in those fibers. Such teaching is set forth, for example, in U.S. Patent No. 5,131,069 to Hall. However, as in the case of tuning and dispersion tuning, until now there has not been a convenient method for tuning or tuning in the field of activity for this specific purpose of the gain of communication signals or signal filtering and / or pumping in a fiber optic transmission system. An additional limitation of the amplifier component or gain block modules used in the currently installed systems involves dynamic gain tilt in multi-channel applications; that is, a change in the gain spectrum with changes in the operating conditions of the components or modules. An amplifier can be designed to provide some optimum level of uniformity in the gain over a given operating band, but it can be achieved generally only for a specific set of input powers and pump powers of the signals. Therefore, if the deployment requirements include a change in signal gain, the uniformity in the gain will be degraded as the general gain spectrum changes. Consider, for example, an optimized multi-channel fiber transmission system that includes at least two amplifier elements typically separated by a distance of approximately 90 kilometers. On this fiber length, the characteristic signal loss due to attenuation and other factors will be approximately -23dB. Each amplifier element is further limited to a power output of approximately 8 dBn / channel by non-linear effects induced to the fiber when the output power is greater than about 8 dBm. Such non-linear effects include, for example, own and cross-phase modulation and mixed four-wave phenomena that are highly detrimental to receiving low-error signals. By simple arithmetic, then, the input power in the next downstream amplifier will be -15 dBm. For these input, loss, and output power values, a saturated average level of inversion can be maintained in an impourified amplifying fiber pumped to provide a relatively uniform gain spectrum of approximately 1536 n at 1560 nm when the fiber is impurified with erbium. Consider now the case in which the distance between the gain elements must be reduced to about 50 kilometers due to a restriction in the placement of the amplifier (p> eg, a mountain or a lake). A characteristic attenuation on this reduced distance would be -13 dB, resulting in a signal power at the input of the next downstream gain element equal to -5 dBM. However, unless the gain of the amplifier element can be reduced such that the power output remains at about 8 dBm, for example, by reducing the excitation current to the source of impurified fiber pumping, the non-linear effects induced in the fiber once again become a problem. It will be appreciated, however, that reducing the gain in the amplifier element by decreasing the average level of investment will lead to the dynamic gain tilt as described above, which must be kept to a minimum for the operation of multi-channel systems . A solution to this problem not hitherto available is presented by the invention described by means of providing a gain platform or an optical amplifier which has a selectively switchable path through one of at least two different lengths of impurified fiber by wherein the output power of the amplifier can be maintained at the desired level substantially independently of the power of higher or lower input signals to maintain the desired gain uniformity over the desired operating band. It is therefore an object of this invention to provide an optical fiber device having switchable characteristics for selecting in the field of activity the variable amounts of optical signal gain, signal filtering and / or signal dispersion in a system of fiber optic transmission and / or an amplifying component thereof. This invention has as an additional objective to provide a component of a fiber transmission system, such as a fiber optic amplifier or an active or passive gain platform, which takes into account the variable and selectable levels in the field of activity of the fiber. the gain of optical signals, the filtering of signals and / or the scattering of signals to selectively send a signal through different fiber lengths having similar or different characteristics. It is a further object of this invention to provide a fiber optic transmission system having variable and switchable amounts in the field of optical signal gain activity, signal filtering and / or signal dispersion.

BRIEF DESCRIPTION OF THE INVENTION Briefly stated and in accordance with a currently preferred embodiment of the invention, a fiber optic device with switchable operation features consists of an input fiber; an optical switch 1 x N optically connected to a second end of a fiber input at a single point of connection of the switch; a first route fiber having known characterization parameters optically connected to a first connection point of the switch; an nth route fiber having known characterization parameters that are different from any other route fiber, connected to an nth point of connection of the switch where a signal propagating in the input fiber to the route fibers can be switched selectively to propagate in one of the N route fibers; an output fiber; and means for optically interconnecting the N path fibers with a first end of the output fiber. In a preferred aspect of this embodiment, the 1 x N optical switch will be an optical switch 1 2. These types of switch are well known to those skilled in the art and do not require detailed discussion except to identify their improved diaphhoty performance over known switches. N x N optics. In addition, the N route fibers are given doped and preferably with a substance that will emit fluorescent light rays in the presence of pumping or excitation energy. Preferred purifying substances i include rare earth elements, for example, erbium, neodymium, praseodymium and others. According to another embodiment of the invention, a fiber optic device with switchable operation features consists of a first fiber to propagate a wavelength of light, and a circulating length of fiber to propagate a wavelength of light, connected to the first fiber between one end of the first fiber and the other end of the first fiber by means of an optical switch to select an optical path of the first fiber to and around the circulating fiber length and again along of the first fiber when the switch is in the connected position, and to select an optical path along the first fiber and not along the fiber circulating length when the switch is in the disconnected position. In the respective aspects of the described embodiment, the device includes a circulating length of dispersion fiber or doped fiber that can act as an optical fiber of signal gain or optical fiber of signal filtration depending on the type and concentration of the dopant, and the presence or absence of optical pumping energy. When the device contains more than a single length of circulating fiber, each length may be different in a particular way; for example, if the device contains three dispersion compensating fiber lengths having a known dispersion, each of the three lengths could be a different length to provide a cumulative overall dispersion compensating effect depending on how few or how many of the lengths They were connected to the optical path of propagation. Of course a similar result could be obtained by a variable number of identical lengths of circulating fiber. It will be appreciated by one skilled in the art that other circulating fiber length parameters such as the type and / or dopant concentration, for example, may be the same or different in each fiber length. In each case, however, the optical switch, known per se, may be a multiplexer / demultiplexer switch for UDM applications. In another embodiment of the invention, an apparatus for amplifying and / or filtering an optical signal includes an optical fiber carrying pump signals, an optical fiber carrying data signals, a fiber-optic element for gain of data signals impuried with a substance that will emit fluorescent light beams in the presence of a pumping signal, an optical coupler for interconnecting the pumping signal transport fiber and the transport fiber. data signals at least at the extreme end of the gain fiber element, and a device including a first fiber having an end connected to one end of the gain fiber element and a circulating length of fiber connected to the first fiber by means of an optical switch, as described above, to select an optical path of the first fiber to and around the circulating length of fiber and again along the first fiber when the switch is in the connected position and to select an optical path along the first fiber and not along and around the circulating fiber length when the switch is in po Disconnected. In the respective aspects of this embodiment, one or more circulating fiber lengths can be configured exactly as described above to provide a gain platform or an optical fiber amplifier having characteristics of switchable gain, filtration or dispersion compensation. . In an alternative aspect of this embodiment, the gain platform or fiber amplifier may contain additional fiber gain elements, as is well known in the art, in which case the switchable device would preferably include circulating lengths of compensating or filtering fiber. dispersion. In an alternative embodiment of the invention, a fiber optic transmission system includes a transmitter and a receiver, at least the first and second transmission fiber links interconnected to the transmitter and the receiver, respectively, and a device which includes a first fiber having one end that interconnects with the first portion of the transmission fiber, and having another end that interconnects with the second portion of the transmission fiber, and a circulating length of fiber connected to the first fiber as described above by means of an optical switch to select an optical path of the first fiber around the circulating fiber length and again along the first fiber when the switch is in the connected position, and p select an optical path along the first fiber and not along and around the circulating fiber length when the switch is is in the disconnected position. In this embodiment, the circulating fiber lengths are preferably dispersion compensating fiber.BRIEF DESCRIPTION OF THE DRAWINGS While the novel aspects of the invention are set forth in the appended claims, the invention itself, together with the objects or additional advantages thereof, can be more readily understood with reference to the following detailed description of the currently preferred embodiment of the invention. invention, considered in connection with the accompanying drawings, in which: Figure 1 is an exemplary schematic view of a device in accordance with this invention having three different lengths either of gain / filtration fiber or dispersion compensating fiber , respectively, each one selectively coupled to an optical fiber transmission / continuous passage through an optical switch. Fig. 2 is a schematic view of a variation of the device in Fig. 1 where the continuous fiber of the device is switchably coupled to a different fiber of transmission / continuous passage for its subsequent control of IDM. Figure 3 is a schematic vieta of an optical fiber transmission system, including a transmitter and a receiver, and device shown in Figures 1 or 2. Figure 4 is a schematic view of the fiber optic transmission system of the Figure 3 including an amplifier component. Figure 5 is a schematic view of an optical amplifier component such as a gain platform including the switchable device of the invention. Figure 6 is a schematic view of the amplifier component of Figure 5 including the single element gain fiber. Figure 7 is a schematic view of the amplifier component of Figure 5 including a double element gain fiber. Figure 8 is a schematic and exemplary view of a device according to another embodiment of the invention having N (N = 2) different lengths of route fiber each coupled selectively optically to an input fiber by means of an optical switch 1 x N (N = 2), and q? e is connected to an output fiber by the appropriate means. Figure 9 is an alternative aspect of the invention shown in Figure 8 in which another branch of route fibers is connected to one or more of the fibers of primary routes.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, an exemplary optical fiber device 10 having switchable characteristics in schematic form is illustrated. The device includes a first continuous-wave fiber waveguide 12 having one end 14 and another end 16. The device 10, as shown, also includes three lengths of circulating fibers 18, each length of circulating fiber 18 being coupled. to the first fiber 12, the intermediate ends 14, 16, by means of a respective optical switch N x N (N = 2) 20. The optical switch 20 is a device well known to those skilled in the art and does not understand at both no invention except to the extent that it is used in combination with the claimed invention described herein. As is known, the optical switch 20 can be a multiplexer / demultiplexer switch to occupy any or any desired wavelengths that are propagating along the fiber 12. For purposes of clarity, the invention will be described in the convention of optical signals that travel from left to right; however, the invention is not limited to such. When one or more optical signals of different wavelengths, such as 980 nm and / or 1550 n, propagate along the first fiber 12, which in practice will interconnect with one or more fibers or devices at the ends. , 16, it is possible to choose that each optimal switch 20 is in the off position in which case the propagation signal will go from point 20 (a) to 20 (b) or point 20 (c) and around- the fiber 18, or it may be chosen that each switch 20 is in the connected position in which case the propagation signal will go from point 20 (a) to 20 (c), around fiber 18 to point 20 (b) back to point 20 (d) and once again on the fiber 12. In this way, for example a signal (i) of sling length of 980 nm and a signal (2) of wavelength 1550 nm could enter into the fiber 12 of the end 14. The switch 20 could be configured in the disconnected position to transport 1 and 2 only along the fiber 12; in the connected position for coupling both 1 and 2 on the fiber 18 and then back to the fiber 12; or, in an aspect where the switch 20, 1 could be prepared only along the fiber 12 while _ selectively traveling on the fiber 18 and then once more on the fiber 12. As such, it is obvious that the device 10 can include 1 to N circulating fiber lengths 18N with the respective switches 20N. In one aspect of the invention, each circulating length of fiber 18 is a dispersion compensating fiber. The device 10 contains N circulating lengths 18, each obtaining a known dispersion value in ps / nrn-km, then a variable amount of dispersion compensation can be selected in real time depending on how many, if any, 18N lengths are connected. to the propagation path. The multiple circulating lengths IBN can be of equal or different length to provide various amounts of dispersion. The device 10 therefore allows the tuning of the activity field or the selection of variable amounts of dispersion (dispersion compensation). In an alternative aspect, each length of circulating fiber 18 consists of a fiber that is doped with a substance that will amplify or absorb (filter) one or more wavelengths of optical signal depending on the composition and concentration of the amplifier in the fiber, and the absence or presence of an optical pump signal in case the dopant is a fluorescent promoter. In a preferred embodiment, the dopant is an appropriate ionic form of a rare earth element such as ervium, for example. Other known fluorescent dopants can be used, including, but not limited to, neodymium and praseodymium, or fluorescent impurifiers such as iron, for example, depending on the type of effect desired of the device. In addition, each circulating length of fiber 18 contains a cut-off wavelength c on the scale from about 900 nm to 1600 nm. It will be appreciated that the device 10 can be commonly interconnected with other fiber portions at the ends 14, 16 either by direct coupling by fusion junction, for example, as shown by the enlarged black dots in Figure 1, or by of interconnecting the ends 14, 16 with the respective optical switches 21, 21 'that are interconnected with a second continuous-pass fiber 30 and are spliced to the other portions of fibers or components as shown in Figure 2. In another embodiment of The invention illustrates an optical amplifying component, such as a passive or active fiber gain or gain platform, with respect to Figure 5-7. A general amplifier component 60 is shown in FIG. 5, in accordance with an aspect of the invention. The component 60 consists of the portion 70 which includes conventional amplifying component parts of a single gain element amplifier component, well known to those skilled in the art, and the switchable device 10. Referring to FIG. 6, an optical pump signal p, and an optical signal of data s are transported with the respective fibers 62, 64. The signal fiber 64 is coupled to the pumping fiber 62 by the coupler IDfl 66, the output 67 of which is connected at the first end 69 of 68 gain fiber doped with rare earth. As is known, various system parameters such as the diameter of the functional mode in the field of activity, for example, will determine whether the pumping fiber or the signal fiber is the fiber directly connected to the gain fiber, or the opposite. As such, Figure 6 (and Figure 7 described below) is purely illustrative of such a design. However, the invention is not limited to the arrangement shown. As the pumping and signal wavelengths propagate through the contaminated fiber 68, preferably an erbium doped fiber, the data signal is amplified in the presence of the pumping signal. The device 10 as described above, is connected to another end 71 of the impurified fiber 68 according to the connection scheme described with respect to Figures 1 and 2, above, in an aspect of the embodiment shown in Figure 6, the device 10 consists of a first continuous-pass fiber 12 and one or more circulating fiber lengths 18 of dispersion-compensating fiber where the data signal can be selectively connected by the switch 20 in order to pass through any combination or one of the fiber lengths 18 to effect a desired amount of dispersion. Alternatively, the fiber lengths 18 can be impurified as described above such that the data signal, if desired, will be further amplified as it passes through each additional length 18 of the doped gain fiber at which the signal from pumping is present to perform an amplifying component with variable accounting gain in the field of activity. In the absence of sufficient remaining pumping power in the lengths 18, or if the dopant is not a fluorescent substance, the device 10 provides attenuation or filtration with the data or pumping signals that are absorbed by the amplifier in the fiber lengths 18. In any case, however, a switchable device is made in the camp >or activity that has variable gain, attenuation or dispersion. Figure 7 schematically shows a dual gain element amplifier component consisting of pumping fiber 62, signal fiber 64, coupler 66, and first and second gain fibers 68, 68 'doped with rare earth, the device 10 being located between the two gain elements 68, 68 '. In this embodiment, the fiber lengths 18 of the device 10 are preferably dispersion compensating fibers, the device 10 being positioned as shown due to the known benefits of locating the dispersion compensating means between the gain elements of the amplifying component. As before, the device 10 can be interconnected to the elements of the gain fibers by any of the two connection schemes illustrated in FIGS. 1 and 2.

Figure 3 schematically shows a fiber transmission system of the invention that includes a transmitter 40 and a receiver 50 at opposite ends of the portions 42, 42 'of a transmission line and the fiber optic device 10 located along of the transmission line between the transmitter and the receiver. In the embodiment illustrated in Figure 3, the device 10 is interconnectable in the system co or is described with respect to Figures 1 and 2, above. Each length 18 of circulating fiber is preferably dewaxing compensating fiber or doped fiber to effect dispersion compensation with filtration, respectively. Figure 4 shows a transmission system of Figure 3 with an optical amplifier component 60, as described with reference to Figures 5-7, included as part of the system. In the embodiment of the invention illustrated in Figure 8, an optical fiber device 100 having switchable operation features includes an input fiber 140 connectable to a transmission fiber adjacent to the component at a first end 141 thereof, and the switch optical 1 x N 200 optically connected to a second end 142 of the input fiber 140 to a single connection point 201 of the switch 200. A first route fiber 150 having known characterization parameters (e.g., length, cut ,, concentration of the dopant, etc.) is optically connected to the first connection point 210 of the switch 200, and an nth route fiber 160 having known characterization parameters and which are different from any other route fiber, is connected to an nth point connection 211 of the switch 200 where the signal propagating in the input fiber 140 to the route fibers can be connected selecti by the switch 200 to propagate on one of the N path fibers. The means 300 is also provided for optically interconnecting the N path fibers with a short end 151 of the output fiber 170, which can still be connected to another fiber component of the second end 172. The interconnector means 300 can consist of any type of passive coupler device or optical switch well known to those skilled in the art. The route fibers 150, 160 are preferably contaminated with a substance that emits fluorescent light rays in the presence of pumping or excitation energy. Typical impurifiers include, but are not limited to, rare earths which include erbium, neodymium, praseodinium and others. The device shown in Fig. 8 is advantageous because, as seen here, a 1 x N 200 switch is more immune to diaphtia and to the effects of multiple path interference than the common N x N optical switches where N is typically the same a 2. An alternative aspect of the embodiment described in connection with Figure 8 is shown in Figure 9. Equal numbers are used to represent features of this aspect of the invention that are common to Figure 8. In that aspect of the invention , the device 100 'consists of other N route fibers 150', 160 'which are respectively connected optically to the route fiber 151 by means of another optical switch 1 x N 200' in an identical manner to that described in connection with the figure 8. A signal propagating in the input row 140 can be selectively sent to the fiber 151 or 152 by means of the switch p > 200. If propagated through the route fiber 151, it can be selectively sent further through another of the route fibers 150 ', 160', and direct to the downlink portion of the route 151 fiber by the means 300 ', and then the output fiber 170 p > Alternatively, it can be propagated in the input fiber 140 and selectively sent to the fiber 152 by means of the optical switch 200, and still be blown through the output fiber 170 by means 300. The embodiments of the invention illustrated in FIGS. 8 and 9 are particularly advantageous for maintaining the uniformity of gain in a fiber amplifier doped substantially independently of the power of the input signal., which is very useful for the operation of multiple channels. The devices 100, 100 'are suitable for construction, as active or passive gain blocks, fiber optic amplifiers, or components in a fiber transmission system that includes a transmitter and a receiver. Although the invention has been described in connection with the presently preferred embodiment thereof, those skilled in the art will recognize that many modifications and changes can be made without departing from the true spirit and scope of the invention, which is intended to be defined only by the attached claims.

Claims (21)

NOVELTY OF THE INVENTION CLAIMS

1. - A fiber optic device with switchable operation characteristics, consisting of: a first fiber to propagate a wavelength of light; and a circulating length of fiber for propagating a wavelength of light, connected to said first fiber between one and other ends of said first fiber by means of an optical switch to selectively provide an optical path of said first fiber to said circulating length of fiber and once more along said first fiber when said switch is in the connected position p > to selectively provide an optical path along said fiber and not along said circulating length of fiber when said switch is in the disconnected position.

2. The device of claim 1, further characterized in that said circulating fiber length is a dispersion compensating fiber or a fiber impurified with the substance capable of amplifying or absorbing said wavelength of light in the respective presence or absence of a pumping signal in said circulating length of fib a.

3. The device of claim 2, further characterized in that said purifying substance i is an appropriate form of a rare earth element.

4. The device of claim 3, further characterized in that said doping substance is an appropriate form of erbium.

5. The device of claim 1, further characterized in that a wavelength of light is included in a wavelength scale from about 900 n to about 1700 n.

6. The device of claim 1, further characterized in that said first fiber and said circulating length of fiber consist of fibers having a cut-off wavelength on a scale of about 900 nm to about 1400 nm.

7. The device of claim 1, further characterized in that said circulating length of fiber consists of a multitude of fiber lengths spaced apart from each other where each length is connected to said first fiber between said one and the other ends by means of a optical switch asated with each fiber length to selectively provide an optical path of said first fiber back to each of said circular fiber lengths and once again along said first fiber when each of said switches asated with each fiber length q? e is in the connected position and to selectively provide an optical path along said first fiber and not along each respective fiber circulating length when each of said switches are in the disconnected position.

The device of claim 1, further comprising one or the other optical switches connected, respectively, to said one and the other ends of the first fiber to interconnect said device to another fiber.

9. ~ An apparatus for amplifying and / or filtering an optical signal, consisting of: a fiber to carry pump signals; a fiber to carry data signals; a gain fiber stage for data signals contaminated with a substance that emits fluorescent light beams in the presence of a pump signal; an optical coupler for interconnecting the pumping signal transport fiber and the data signal transport fiber or gain fiber stage end; and a device including a first fiber having one end connected to another end of the gain fiber stage and a circulating length of fiber connected to said first fiber between said one end and another end of the first fiber by means of a optical switch for selectively providing an optical path of said first fiber to said circulating length of fiber and once again along said first fiber when said switch-is in a position to be connected selectively to provide an optical path along said first fiber and along said circulating length of fiber when said switch is in the disconnected position.

10. - The apparatus of claim 9, further characterized in that said circulating length of fiber is a dispersion compensating fiber and a fiber impurified with a substance capable of amplifying or absorbing said wavelength of light in the respective presence or absence of a pumping signal in said circulating fiber.

11. The apparatus of claim 10, further characterized in that said doping substance is an appropriate form is a rare earth element.

12. The apparatus of claim 9, further characterized in that said first fiber and said circulating length of fiber consist of fibers having a cut-off wavelength on a scale of apr-about 900 nm to about 1400 nm.

13. The apparatus of claim 9, further characterized in that said circulating length of fiber consists of a multitude of fiber lengths spaced apart from each other wherein each length is connected to said first fiber between said one and other ends of said fiber by means of of an optical switch associated respectively with each fiber length to selectively prive an optical path of said first fiber to each respective circulating fiber length and once again along said first fiber when each of said switches associated respectively with each Fiber length is in the connected position and to selectively provide an optical path along said first fiber and not along said circulating length of fiber when each of said switches is in the disconnected position.

14. The apparatus of claim 9, which further comprises more than one and other optical switches respectively connecting said one end of the first fiber and said other end of the gain fiber stage, and said other end of said fiber. the first fiber and another length of the transmission fiber, in parallel with a length of the transmission fiber interconnecting said other end of the gain fiber stage and said other length of the transmission fiber.

15. The apparatus of claim 9, comprising more than a second step of gain fiber of the data signals contaminated with a substance that emits fluorescent light beams in the presence of the pumping signal, interconnected to said signal. another end of said first fiber at a first end of said second fiber gain stage of the data signals.

16. The apparatus of claim 15, further characterized in that said circulating length of fiber consists of dispersion compensating fiber.

17. The apparatus of claim 13, further characterized in that said lengths of circulating fibers are selected from among (a) equal fiber lengths having equal amounts of dispersion; (b) equal fiber lengths having unequal amount of dispersion; or (c) unequal fiber lengths.

18. The apparatus of claim 16, further comprising one or the other optical switches respectively connecting said one end of the first fiber and said other end of the gain fiber stage, and said other end of the first fiber. fiber and said first end of said second fiber gain stage of the data signals, at p > A parallel with a transmission fiber length q and said other end of the gain fiber stage and said first end of said second gain fiber stage of the data signals interconnects.

19.- A fiber optic device with switchable operation characteristics, consisting of: an input fiber; an optical switch 1 x N optically connected to a second end of the input fiber at a single point of connection of the switch; a first route fiber having known characterization parameters optically connected to a first connection point of the switch; an umpteenth path fiber that has known characterization parameters and that are different from any other route fiber, connected to an nth point of connection of the switch where a signal that propagates in the input fiber to the path fibers can be selectively connect to propagate on an N path fibers; an output fiber; and means for optically interconnecting the N path fibers with a first end of the output fiber.

20. The device of claim 19, further characterized in that the N route fibers are contaminated with a substance that emits fluorescent light rays in the presence of pumping energy.

21. The device of claim 19, which further comprises another 1 x N optical switch optically connected to any of the N path fibers at a first connection point of another 1 x N optical switch on the optical switch 1 x N and the interconnector means; other N route fibers connected to other N connection points of the other switch; and other means for interconnecting the other N path fibers to one of the N downstream path fibers of the other 1 x N optical switch.