JP2002544557A - Amplitude adjustable filter - Google Patents

Abstract

Abstract: A dynamically tunable filter (10) provides a coupling between the core (16) and cladding (18) modes by surrounding the waveguide with an overclad (20) having an adjustable refractive index. Control the size. Such a coupling mode is reduced along the core producing the desired spectral response. Adjustment of the refractive index of the over cladding (20) is performed in a range larger than the refractive index of the lower cladding (18), thereby changing the size of the attenuation wavelength band without shifting the center wavelength of the band. Let it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD OF THE INVENTION

This application claims the benefit of US Provisional Patent Application No. 60 / 134,565, filed May 17, 1999. Coupling of light between the core and cladding layers of an optical waveguide affects the transmission characteristics of the waveguide's spectrum. External control is to modify the coupling parameters to change the transmission characteristics or to make “adjustments”.

[0002]

BACKGROUND OF THE INVENTION

Spectral transmission characteristics are dependent on the material of the waveguide (eg, fiber) and its geometry, as well as in-line optical devices, including routers, filters and amplifiers, and various interactions with signals as well as environmental factors. Affected by
Optical amplifiers often produce substantially non-uniform gain over the operating spectral range and are used in conjunction with gain flattening filters, including thin films, long-period gratings, and fiber Bragg gratings, to achieve the desired spectral characteristics. maintain.

[0003] Additional gain flattening is often required at the system level, especially in underwater applications. As with other in-line systems, the gain ripple of the amplifiers in a row accumulates and generates system ripple that can also be mitigated by other gain flattening filters. Such filters are fixed with a spectral response that can be adapted to the requirements of a particular system. However, some system-wide changes change over time, as do other more local changes. Changes in environmental conditions and system perturbations, including the aging of the system, can change the spectral transmission distribution of the system in a transient and unpredictable way. Dynamic adjustment of the spectrum is necessary to maintain system stability.

[0004] Tunable filters, particularly tunable fiber Bragg gratings, can take advantage of the spectral response that can be shifted along the spectrum. Filter gratings are tuned by changing their periodicity, for example, under the control of external forces such as compression or stress. However, its time-varying system spectral transmission characteristics do not readily have a reaction by performing a narrow attenuation band shift. Shifting the attenuation band, particularly for signals closely spaced along the spectrum, can disrupt adjacent signals. Some short-period gratings reduce the spectral band by reflection, which requires additional system complexity to condition or eliminate the reflected light.

[0005]

Summary of the Invention

Improved tuning capability is provided primarily by scaling the filter response, rather than shifting the wavelength response. Within a predetermined wavelength range, the overall amplitude of the reduced spectral band can be increased or decreased without significantly changing the center wavelength of the reduced band. This band can be reduced by extinction rather than reflection. And, the novel amplitude tunable filter of the present invention can be combined with other tunable or passive filters to provide a wider system response or individually adjust the transmission characteristics of different channels.

[0006] The preferred embodiment according to the invention relies on a special coupling mechanism with a dynamic tuning effect found at the present time. Long-period gratings, tapered paths, and other perturbations can be used along the optical waveguide to couple light from the core to the surrounding cladding. The environmental conditions surrounding the cladding affect the cladding mode.

For example, in “Optics Letters”, Vol. 22, No. 23, December 1, 1997, “Displacements of Response of Long-Period Fiber Grating Caused by Change in Refractive Index Around the resonant peaks of al
ong-period fiber grating induced by a change of ambient refractive index
) "Discusses the effect of surrounding the cladding of a long-period grating with media having different surrounding indices of refraction. When the refractive index is lower than the cladding refractive index, the cladding mode attenuation band shifts to a lower wavelength side, and the amplitude decreases as the surrounding refractive index approaches the cladding refractive index. For the ambient index that matches the cladding index,
Since the cladding mode is no longer guided, the attenuation band substantially disappears.
Above the cladding index, the attenuation band reappears, and the amplitude increases with a further increase in the ambient index, but does not shift in wavelength. The preferred embodiment of the novel amplitude tunable filter according to the invention takes advantage of this latter spectral coupling behavior.

An embodiment of an amplitude tunable filter according to the present invention has a waveguide including a core and a cladding that guides light in a desired wavelength range along the core. The coupler couples at least one band of wavelengths from the core to the cladding. The over cladding covers at least a part of the cladding and exhibits a refractive index higher than the highest value of the refractive index of the cladding. In addition, the refractive index of the over cladding can be changed by external control. A controller for this purpose adjusts the refractive index of the overcladding in a range higher than the refractive index of the cladding to change the amplitude of the coupled band of the cladding without significantly shifting the center wavelength of the band.

The coupler is preferably a long period grating formed along the waveguide, but a tapered or grating filter, fused fiber device or other coupling structure that couples the core transmission to the cladding mode. You may. The coupler is located along the waveguide within the area covered by the overcladding, and is preferably adiabatic to suppress shifting of the center wavelength of the coupled band as a function of waveguide temperature. In contrast, preferably, the overcladding
It exhibits a refractive index that varies substantially as a function of temperature. In a preferred embodiment, the overcladding is an organic optical material having a negative dn / dT. A particularly preferred embodiment of the overcladding is an inorganic-organic hybrid material called a hybrid sol-gel material, which has a substantially higher refractive index (eg, 1.47-1.55) than a typical silica cladding. And has a refractive index change rate (dn / dT) with respect to a temperature of about -3 × 10 ^-4 . The hybrid material preferably has at least some silicon atoms directly bonded to a substituted or unsubstituted hydrocarbon moiety,
Includes an extended matrix containing silicon and oxygen atoms. In the solid state, this hybrid material provides structural support and protection to the core and underlying layers of the cladding,
The bending resistance for protecting the grating performance can also be adjusted.

[0010] The controller preferably changes the refractive index of the over cladding within a range higher than the refractive index of the cladding by operating a temperature conditioner for adjusting the temperature of the over cladding. For example, the temperature conditioner can be formed as a heater with electrical resistance in thermal contact with the overcladding. Other heaters or coolers may be used to produce the desired range of overcladding temperature changes corresponding to a range of overcladding refractive index higher than the cladding.

The present invention can also be said to be a system for adjusting the amplitude of a cladding mode coupled wavelength of a light beam without significantly shifting the coupled wavelength of the light beam. Such adjustment is achieved by modifying the coupling between the core and the cladding, with the overcladding having a higher refractive index than that of the cladding. The over cladding refractive index varies within a range of refractive indices wider than the cladding refractive index as a function of external control given by changing the over cladding refractive index.

[0012] Preferably, the baseline system wide spectrum response is provided by a combination of passive filters. The change in system response from baseline is counteracted by one or more amplitude tunable filters. Preferably, a plurality of amplitude tunable filters are linearly coupled with the passive filters to produce a combined spectral response. Preferably, each of the amplitude tunable filters reduces a substantially unique band of the system spectrum. The amplitudes of the reduced bands can be individually adjusted to maintain the desired spectral transmission characteristics.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

The tunable amplitude filter 10 shown in FIGS. 1 and 2 includes a long-period grating 12 formed by an insulated waveguide 14 (a waveguide arranged to suppress thermal spectral shift). A preferred embodiment of the insulated waveguide 14 is December 11, 1997.
U.S. patent application Ser.
Athermalized Codoped Optical Waveguide Device), which is hereby incorporated by reference. According to this embodiment, the waveguide
The 14 cores 16 and the surrounding cladding 18 are mainly formed of silica. However, the core 16 is doped with a dopant that increases the refractive index, such as GeO ₂ , to guide the light, and has a dopant, such as B ₂ O ₃ , that acts opposite to the temperature effect of the dopant. Next is added. The molar ratio of the primary dopant to the secondary dopant is preferably in the range 1.5: 1 to 8: 1 and is selected to neutralize the thermal sensitivity of the waveguide.

The thermally insulated waveguide 14 can form a silica core 16 to which GeO ₂ has been added and B ₂ O ₃ has been additionally added by flame hydrolysis using an external method. The silica cladding 18 that may also be formed preferably includes a further small amount of B ₂ O ₃ to make the waveguide 14 more stable. The vapor storage levels of these materials are sent to a flame hydrolysis burner to provide the desired material concentrations in core 16 and cladding 18. Other waveguide adiabatic approaches can be used including compensating for thermally induced changes in refractive index with changes in strain.

The GeO ₂ concentration of the core 16 also provides photosensitivity for writing the long-period grating 12. The core 16 is exposed to a periodic band of ultraviolet light that changes the refractive index of the alternating axis portion 22 of the core 16. The alternating portions 22 can be individually exposed by moving the waveguide 14 and the ultraviolet light source relative to each other. Alternatively, exposure can be performed at once by a masking method.

Surrounding the waveguide 14 in the region of the long period grating 12 is provided by an overclad 20 having a higher refractive index than the cladding 18. Preferably, the refractive index of the overcladding 20 is sensitive to temperature changes and exhibits a refractive index proportional to the temperature change. Preferred overcladding of the present invention is a hybrid sol-gel,
Preferably in the solid state, U.S. Patent No. 5,991,493, entitled "Hybrid Organic-Inorganic Planar Optical Waveguide
Device) ", which is incorporated herein by reference. Additional applications disclosing similar materials suitable for use as overcladding 20 can also be found in U.S. application Ser.No. 09 / 494,073, which was issued in 1999.
U.S. Provisional Application No. 60 / 118,946 filed February 5, and International Application filed December 12, 1997
Claims the benefit of PCT / US97 / 22760. These applications are also incorporated by reference herein.

The sol-gel material consists of an expanded matrix comprising silicon and oxygen atoms, preferably with at least some silicon atoms directly bonded to substituted or unsubstituted hydrocarbon moieties. The index of refraction of the sol-gel material can be set from a little above the index of refraction of the silica cladding 18 to a wide range, including a range of about 1.55 measured at 588 nanometers. Adjustment to the refractive index is performed using aryl trialkoxysilane (
Phenyltrialkoxylate), or allyltrifluorosilane (especially phenyltrifluorosilane), which can be combined to increase the ratio to silicon to increase the refractive index.

For example, a target index of refraction of about 1.47 at 20 ° C. at a wavelength of 1550 nanometers is set in the sol-gel material, which is determined by the ratio of phenyl to methyl groups. A composition formed from 8 mol% polydimethylsiloxane, 52% methyltriethoxysilane, 31% phenyltriethoxysilane and 9% phenyltrifluorosilane is combined to form a sol-gel material with a reference index of 1.47. It can be hydrolyzed to form.

FIGS. 3A-3D, which plot the typical effects of discrete changes in the index of refraction “n” of the surrounding medium on different cladding modes, are shown in September 1998, Lightwave Technology, Vol. 16, No. 9, “Analysis of the Response of Long Period Fiber Grating to External Refractive Index”
ber Gratings to External Index of Refraction).
Such articles are hereby incorporated by reference. Due to the different mode field distributions, the higher-order modes “i ₄ -i ₇ ” are replaced by the lower-order modes “i _1-
It is more susceptible to external refractive index changes than i ₃ . Also, of particular importance,
The center of the wavelength of all of the band "i ₁ -i _7", "λ ₁ -λ _5" remains substantially unchanged.
The tunable filter 10 of the present invention preferably operates within a range in which a change in the refractive index of the overclad 20 causes a large change in the amplitude of the clad-coupled band (eg, i ₄ -i ₇ ).

The refractive index of this sol-gel material is affected by temperature with a rate of change of about −3 × 10 ⁻⁴ / ° C. = dn / dT. Where dn is the change in refractive index and dT is the change in temperature in degrees Celsius. Increasing the temperature of the sol-gel material of the overcladding 20 reduces the coupling intensity and the corresponding amount of attenuation of the longer coupled spectrum band without shifting the center wavelength of these bands.

Other materials that give similar changes in the refractive index as a function of temperature, especially polymers,
It may be used as the over cladding 20. Polymers having a temperature-sensitive refractive index (e.g., UV-curable acrylate-based polymers) are described in AAAbramov, Vol. 35, No. 1 of Electronics Letters, Jan. 7, 1999.
"Widely tunable fiber grating (Widely tunable
long-period fiber gratings), which is hereby incorporated by reference. The refractive index of the polymer is preferably adjusted to vary within a range higher than the refractive index of the preferred cladding material, silica.

A temperature conditioner 24, for example, an electric resistance heater, is in thermal contact with the overcladding 20. The current to the heater can be controlled to regulate the temperature of the overcladding 20 and to cause a change corresponding to a change in the refractive index of the overcladding 20. A cooler may be used instead of or in addition to a heater to vary the overcladding temperature over a wider range. However, the amount of overcladding temperature change is preferably in a range where the grating 12 is adiabatic to avoid wavelength shifts caused by temperature changes in the core 16 and cladding 18. A temperature conditioner 24 may be formed inside the housing of the tube 26 to provide structural support to prevent bending or other disturbances of the grating 12.
Other installations may be performed, for example, by attaching the waveguide 14 to a rigid substrate (eg, a glass plate).

To vary the amount of attenuation, the spectral bands are protected against wavelength shifts in several ways. The grating waveguide 14 is insulated. The refractive index of the over clad 20 changes in a range larger than the refractive index of the clad 18. The waveguide 14 is also supported against bending. Over cladding 20
Thermal protection of the waveguide 14 is necessary because the temperature change caused by it controls the amplitude of the spectral band. However, other mechanisms, including pressure and electronic optics, may be used with other overcladding materials to control the refractive index.

FIG. 4 plots the spectral response of the amplitude tunable filter 10 at three different temperatures with respect to decibel loss in the wavelength domain.
Two spectral bands' and _'1' i i '' ₂ "is clear. 3 plot lines
30, 32 and 34 correspond to temperatures of −10 ° C., 20 ° C. and 80 ° C., with the largest difference within the higher spectral band “i ′ ₂ ”. Spectral band "i _'2" at -10 ℃
Exhibits a spectral loss of 6 dB, and at 80 ° C. the loss is less than 4 dB.
Again, higher order cladding modes show more pronounced amplitude effects with temperature. However, higher order modes also become less stable and become more dependent on environmental interactions. Hence, a middle is needed between amplitude control and filter stability.

The operating range of the amplitude adjustable filter 10 as a band reject filter can be selected from the design of the grating 12 to cover the desired range of attenuation. The overcladding 20 preferably covers the entire length of the grating 12, but may cover a shorter length to provide chirping of the response. Another amplitude tunable filter 40 shown in FIG. 5 is formed along a waveguide 42 having a tapered cross section 44 that is tapered to force coupling from core 46 to cladding 48. For example, a temperature-sensitive overcladding 50, such as a sol-gel, surrounds the tapered cross-section 44. The overcladding 50 exhibits a refractive index higher than the refractive index of the cladding 48, and preferably varies in refractive index as a function of temperature within a range maintained above the refractive index of the cladding 48. A temperature conditioner 52, such as a heater or cooler, controls the temperature of the overcladding 50 to adjust the amplitude of the spectral band reduced by the filter 40. Tube 54 provides structural support.

In response to the cladding modes coupled by the filter 40, the spectral bands include the dimensions and refractive index of the over cladding 50, as well as the taper dimensions and refractive index distribution of the core 46 and cladding 48, Influenced by design considerations. However, once selected, the spectral position of the band is preferably invariant to changes in temperature or refractive index of the overcladding 50 that are within a range of refractive indices greater than that of the cladding 48. . Other mechanisms, including pressure or electro-optic effects, may be used instead of temperature to provide the desired control over the refractive index of the overcladding 50. Amplitude control provided by filter 40 and other filters that can reduce the range of wavelengths can also be used to affect the overall shape (eg, slope) of the filter response. The resulting attenuation can be wavelength dependent (eg, increasing with wavelength) resulting in a sloping filter response. Another effect on the shape of the filter response is
For the downstream coupler, it can be manufactured by adjusting the position, length or axial thickness distribution of the overcladding.

As shown in FIG. 6, a novel amplitude optical filter 62 according to the present invention comprises an optical system
It can be used with a conventional filter 64 to control all 60 spectral responses. Conventional filter 64 compensates for the steady state portion of the system response error, and the amplitude adjustable filter of the present invention covers a portion of the system spectrum for changes over time. The filter response depth is preferably limited to reduce polarization dependent losses. However, the desired dynamic range of amplitude changes can be achieved by combining one or more of the amplitude adjustable filters 62 that can adjustably reduce the same spectral band.

A system spectral response monitor 66 connected via a fiber coupler 67 (eg, a one percent tap) includes a processor 68 and a driver 70 (eg, a heater driver) for controlling the novel amplitude tunable filter 62 according to the present invention. ), Which responds to changes in the amplitude of the system spectrum, working together as a dynamic equalizer. Monitoring of the system spectral response and subsequent amplitude control can be performed continuously. Alternatively, monitoring may be performed intermittently, occasionally adjusting the response of the amplitude adjustable filter 62 according to the present invention.

The present invention is shown as the optical amplifier module 80 in FIG. Module 80
It can be inserted along the optical path 82 of a larger optical system (not shown). Inside the module 80, an optical amplifier 84 (eg, an erbium-doped fiber amplifier),
There is a spectrum monitor 86, a gain flattening filter 88, and a controller 90. Portions of the controller 90, such as a logic board or processor, may be connected to the outside of the module 80. However, preferably, a gain flattening filter
The actual control of 88 is completely within the scope of module 80.

A spectrum monitor 86, such as a 1 percent tap, connected to the optical path 82 via a fiber coupler 87 provides information about the spectral gain distribution of the gain flattening filter 88 to a controller 90. The individual components 92, 94 and 96 of the gain flattening filter 88 are independently controllable to reduce the different spectral bands of the gain distribution. Preferably, the filter components 92, 94 and 96 have a structure similar to the embodiment of FIG. 1 or 5, but other amplitude adjustable components may be used. Controller 90 drives drivers 98, 100 and 102 associated with each filter component 92, 94 and 96 to adjust the amplitude of the spectral band without significantly shifting the center wavelength of the band. The resulting filter response distribution compensates for unnecessary changes in the monitored gain distribution.

A passive filter (not shown) can also be incorporated into module 80 to provide a modification of the baseline spectrum that can be further modified by controllable components 92, 94 and 96. The gain flattening filter 88 can also be controlled to provide dynamic equalization, where the monitored gain distribution is a system change, including component or fiber insertion loss changes, changes in input signal power, add or drop. It reflects changes related to channels, environmental changes, and changes related to aging and other cumulative effects.

Other filters, including grating filters and fused fiber device devices, can also benefit from the present invention, especially where the coupling between core and cladding modes is due to the change in the refractive index of the outer overcladding. Can be affected. A variable refractive index overcladding can be mounted both within and between the grating filter components to further manage the spectral response. In addition to implementing the novel amplitude tunable filter according to the invention in a fiber structure, similar benefits can be obtained in planar structures. Preferably, the over cladding and the control layer are
It is placed opposite the two layers of the cladding with the core layer in between to manage polarization dependent losses.

Those skilled in the art will recognize that other modifications and variations can be made by the structure, composition and method of the present invention without departing from the spirit or aspects of the invention.

[Brief description of the drawings]

FIG. 1 is an axial sectional view of an amplitude-tunable filter according to the present invention including an insulated fiber grating surrounded by an overcladding and a thermal conditioner.

FIG. 2 is a cross-sectional view of the filter taken along line 2-2 of FIG.

FIG. 3A is a graph of a potential filter response comparing the effect of different overclad refractive indices within a range higher than the lower cladding refractive index.

FIG. 3B is a graph of a potential filter response comparing the effects of different overclad refractive indices within a range higher than the lower cladding refractive index.

FIG. 3C is a graph of a potential filter response comparing the effects of different overclad refractive indices within a range higher than the lower cladding refractive index.

FIG. 3D is a graph of a potential filter response comparing the effects of different overclad refractive indices within a range higher than the lower cladding refractive index.

FIG. 4 is a graph of the filter response over a shorter wavelength region comparing the effect of three different temperatures of the overcladding.

FIG. 5 is an axial cross-sectional view of an amplitude-adjustable taper filter surrounded by a temperature-adjusting overcladding.

FIG. 6 is a diagram of an optical system that includes a plurality of conventional filters and a plurality of amplitude adjustable filters according to the present invention.

FIG. 7 is a diagram of an optical amplifier module including a gain flattening filter together with an amplitude adjustable filter module.

──────────────────────────────────────────────────続 き Continuation of front page (81) Designated country EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, IT, LU, MC, NL, PT, SE ), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, CH, CN, CU, CZ, DE, DK, EE, ES, FI, GB, GD, GE , GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK, LR, LS, LT, LU, LV, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL, TJ, TM, TR, TT, UA, U G, UZ, VN, YU, ZA, ZW (72) Inventor Conc Glen E. 14870 Painted Post West High Street 310 (72) Inventor Weller-Brophy Laura A. United States of America New York 14830 Corning Pine Lane 6F Term (Reference) 2H038 AA22 AA31 BA25 BA27 2H050 AB42Y AC36 AC82 AC83 AC84 AD00 2H079 AA06 BA01 CA04 CA07 DA07 EA09 EB27 KA08 KA11

Claims (70)

[Claims] 1. A waveguide comprising a core and a cladding, the waveguide guiding light in a wavelength range along the core, and a band having at least one of the wavelengths from the core and having a center wavelength. A coupler coupled to the cladding, having a refractive index higher than the refractive index of the cladding and having a refractive index that is changed by external control, and an over cladding surrounding at least a portion of the cladding; and in a range higher than the refractive index of the cladding. A controller for adjusting the refractive index of the over cladding and changing the amplitude of the center wavelength of the band without substantially moving the center wavelength of the band. . 2. The filter of claim 1 wherein said coupler is adiabatic so that changes in said center wavelength of said band are suppressed as a function of waveguide temperature. 3. The filter of claim 2, wherein said overcladding has a refractive index that varies as a function of temperature. 4. The filter according to claim 3, wherein the over cladding is made of an inorganic-organic hybrid material. 5. The filter of claim 4, wherein said hybrid material comprises an expanded matrix comprising silicon and oxygen atoms having at least some of the silicon atoms directly attached to a substituted or unsubstituted hydrocarbon moiety. . 6. The filter according to claim 3, wherein the over cladding is made of a polymer. 7. The controller according to claim 1, wherein the controller drives a temperature conditioner that adjusts the temperature of the over cladding to change the refractive index of the over cladding within a range higher than the refractive index of the cladding. The filter according to claim 3. 8. The filter according to claim 7, wherein the temperature conditioner is an electric resistance heater in thermal contact with the overcladding. 9. The filter according to claim 7, wherein said temperature conditioner is a cooler in thermal contact with said overcladding. 10. The filter according to claim 1, wherein the coupler is located in the waveguide in a region covered by the over cladding. 11. The filter of claim 10, wherein the coupler functions as a filter that exhibits a spectral response with at least one of the reduced wavelengths corresponding to a band coupled from the core to the cladding. The filter described. 12. The filter according to claim 11, wherein the coupler is a long-period grating. 13. The filter according to claim 1, wherein the coupler is a tapered portion of the waveguide having a core dimension decreasing along a light propagation axis direction. 14. The filter according to claim 13, wherein the over cladding covers the tapered portion of the waveguide. 15. The filter according to claim 1, wherein the waveguide is fixed to prevent bending. 16. The coupling according to claim 1, wherein the coupling is one of a plurality of couplings formed along the waveguide, at least a portion of which has a refractive index higher than a refractive index of the cladding. The filter according to claim 1, wherein the filter is covered by an over cladding. 17. The filter of claim 16, wherein each of the couplings connects at least one of a plurality of spectral bands each having a center wavelength from the core to the cladding. 18. The controller drives a plurality of drivers for adjusting the refractive index of the over cladding within a range higher than the refractive index of the cladding, and drives the plurality of drivers without significantly shifting the center wavelength of the same band. 18. The filter according to claim 17, wherein an amplitude of a center wavelength of the band is changed. 19. The filter of claim 1, wherein the overcladding is a solid material that provides structural support to the portion of the waveguide where the coupler is formed. 20. A coupling between a core and a clad is corrected by an overcladding having a refractive index higher than the refractive index of the cladding, and the overcladding is performed within a range of a refractive index larger than the refractive index of the cladding. A system for adjusting the amplitude of a cladding mode coupled band of a light beam according to a change as a function of external control provided by varying the refractive index of the cladding without significantly shifting the wavelength of the coupled band. 21. The system of claim 20, wherein the core, the cladding, the overcladding, and the external controller form an amplitude tunable filter that compensates for a system spectral characteristic that varies as a function of time. . 22. The tunable amplitude filter of claim 1, wherein the tunable filter is one of a plurality of tunable filters that vary the amplitude of different spectral bands of the spectrum intended for transmission by the system. 21. The system according to 21. 23. The system of claim 22, including at least one passive filter that compensates for unequal system spectral transmission characteristics that do not change as a function of time. 24. The system of claim 20, wherein the coupling is formed by perturbation of the core. 25. The system of claim 24, wherein said core perturbation is a long period grating. 26. The system of claim 24, wherein the core perturbation is a taper that gradually reduces the size of the core. 27. The system of claim 20, wherein the coupling is formed by a series of core perturbations connecting different bands of the system spectrum. 28. The external control of claim 27, wherein the external controller is one of a plurality of external controls that change the amplitude of a coupled band without shifting the center wavelength of the band. system. 29. The system of claim 20, wherein the coupling is adiabatic so as not to significantly shift the wavelength of the coupled band as a result of a change in temperature of the core. 30. The overcladding is a solid material that provides structural support to the core and lower layers of the cladding to prevent bending.
20 described system. 31. The system of claim 20, wherein the overcladding has a refractive index that changes as a function of temperature. 32. The system of claim 31, wherein the overcladding is an inorganic-organic hybrid material. 33. The system of claim 32, wherein said hybrid material comprises an expanded matrix comprising at least some silicon atoms and silicon and oxygen atoms directly bonded to substituted or unsubstituted hydrocarbon moieties. . 34. The system of claim 32, wherein said hybrid material is a polymer. 35. The external controller, provided by a temperature conditioner that adjusts the temperature of the over cladding, changes the refractive index of the over cladding within a range higher than the refractive index of the cladding. Claims
31. The system according to 31. 36. The system of claim 20, wherein the external controller includes a system spectral response monitor and a processor that determines an appropriate adjustment of the refractive index of the overcladding. 37. The coupling, wherein the coupling is one of a plurality of couplings,
37. The system of claim 36, wherein the external controller includes a driver for adjusting the size of the coupling according to the adjustment determined by the processor. 38. A method for compensating for a transmission characteristic of a spectrum that varies as a function of time, the method comprising monitoring a spectral transmission characteristic of a system having a spectral range that includes at least one spectral band whose transmission characteristic varies with time. And adjusting the amplitude of the spectral band without significantly shifting the center wavelength of the band to compensate for changes in transmission characteristics. 39. The method of claim 39, further comprising guiding light in the spectral band along a waveguide having a core surrounded by a cladding.
38. The method according to 40. The method of claim 39, wherein said reducing comprises coupling the spectral band to the surrounding cladding. 41. The method of claim 40, further comprising the step of covering the cladding over at least a portion of the cladding with an overcladding having a refractive index higher than the refractive index of the cladding. 42. The adjusting step changes the refractive index of the overcladding within a range higher than the refractive index of the cladding, and does not significantly shift the center wavelength of the band, without changing the amplitude of the spectral band. 42. The method of claim 41, comprising the step of: 43. The changing step includes changing a temperature of the over cladding to change a refractive index of the over cladding within a range higher than a refractive index of the cladding. Item 42. The method according to Item 42. 44. The method of claim 43, wherein said overcladding is an inorganic-organic hybrid material. 45. The hybrid material of claim 44, wherein the hybrid material comprises an expanded matrix comprising at least some silicon atoms and silicon and oxygen atoms directly bonded to a substituted or unsubstituted hydrocarbon moiety. Method. 46. The method of claim 43, wherein said overcladding is a polymer. 47. The method of claim 43, wherein the step of guiding includes preserving the center wavelength of the band independent of changes in the temperature of the overcladding. 48. The method of claim 38, wherein the reducing comprises reducing different spectral bands whose transmission characteristics change over time. 49. The adjusting step includes a step of individually adjusting an amplitude of the spectral band without largely shifting a center wavelength of the band to compensate for a change in transmission characteristics of the band. 49. The method of claim 48, wherein the method is characterized by: 50. The method of claim 49, wherein reducing the plurality of different spectral bands comprises passively reducing some bands by different amounts. 51. A waveguide that includes a core and a cladding, and guides light of a range of wavelengths along the core, and covers a portion of the cladding along a length of the waveguide, and the cladding includes: An over cladding having a refractive index higher than that of the over cladding, and a plurality of bands of wavelengths each having a central wavelength located in a portion of the waveguide covered by the over cladding and connecting to the cladding from the core. The arrangement of the coupler, the refractive index of the overcladding, which is changed by external control, and adjusting the refractive index of the overcladding within a range higher than the refractive index of the cladding, to greatly shift the center wavelength of the coupled band. And a controller for changing the amplitude of the center wavelength of the coupled band. 52. The filter of claim 51, wherein the coupler is insulated to prevent a shift of a center wavelength of the band as a function of a temperature of the waveguide. 53. The filter of claim 52, wherein said overcladding has a refractive index that varies as a function of temperature. 54. The filter according to claim 53, wherein the over cladding is an inorganic-organic hybrid material. 55. The filter according to claim 53, wherein the overcladding is a polymer. 56. The controller drives a plurality of temperature conditioners for adjusting the temperature of the over cladding, and changes the refractive index of the over cladding within a range higher than the refractive index of the cladding. 54. The filter of claim 53, wherein 57. The controller receives information from a spectrum monitor regarding a gain distribution of an amplifier and drives a plurality of drivers that adjust a refractive index of another overclad to compensate for a spectrum change in gain. Claims
Filter according to 51. 58. The filter according to claim 51, wherein said coupler includes at least one long period grating. 59. The filter according to claim 51, wherein said coupler comprises at least one tapered coupler. 60. An optical amplifier module having a plurality of components interconnected within a module, the components monitoring an optical amplifier exhibiting a spectral gain distribution, and monitoring the spectral gain distribution of the optical amplifier. A spectrum monitor, a gain flattening filter including a plurality of individually controllable filter components for reducing the different spectral bands of the gain distribution, and adjusting the amplitude of the spectral band without significantly shifting the center wavelength of the band; An optical amplifier module, comprising: a controller for compensating for an unnecessary change in the gain distribution. 61. The controllable filter component, wherein the filter component comprises a core along a waveguide, a cladding, and an overcladding covering a portion of the cladding along a length of the waveguide. 62. The module of claim 60, wherein the module is formed along a wave path. 62. The module of claim 61, wherein the overcladding portion has a higher refractive index than the cladding. 63. The arrangement of the coupler is located within a portion of the waveguide covered by the over cladding and coupling the cladding to the plurality of spectral bands from the core. Module according to 62. The controller adjusts the refractive index of the overcladding portion within a range higher than the refractive index of the cladding, and does not significantly shift the center wavelength of the band to be coupled. 64. The module of claim 63, wherein the amplitude of the center wavelength of a band is varied. 65. A dynamic equalizer for reducing amplitude variations in the spectrum of a fiber optic system, comprising: a waveguide including a core and a cladding, for guiding light of a range of wavelengths along the core; An overcladding that covers a portion of the cladding along the length direction and has a refractive index higher than a refractive index of the cladding; and An array of couplers for coupling a plurality of wavelength bands having wavelengths from the core to the cladding, a refractive index of the overcladding that changes by external control, and a spectrum monitor that monitors changes in a spectrum amplifier of the fiber optical system. Responding to changes in the amplitude of the monitored spectrum, within a range higher than the refractive index of the cladding. Bar refractive index was adjusted in the cladding, the equalizer, characterized in that comprising the controller to vary the amplitude of the central wavelength of the coupling band, without increasing shift the center wavelength of the binding band. 66. The equalizer of claim 65, wherein the coupler is adiabatic to prevent the center wavelength of the band from changing as a function of waveguide temperature. 67. The equalizer of claim 66, wherein said overcladding has a refractive index that varies as a function of temperature. 68. The equalizer according to claim 67, wherein the over cladding is an inorganic-organic hybrid material. 69. The overcladding is a polymer.
The equalizer according to 67. 70. The controller activates a plurality of temperature conditioners for adjusting the temperature of the over cladding, and changes the refractive index of the over cladding within a range higher than the refractive index of the cladding. Claim 67 characterized by the claims
Equalizer as described.