WO2000041012A1 - Bandwidth-variable optical filter - Google Patents

Bandwidth-variable optical filter Download PDF

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Publication number
WO2000041012A1
WO2000041012A1 PCT/KR1999/000836 KR9900836W WO0041012A1 WO 2000041012 A1 WO2000041012 A1 WO 2000041012A1 KR 9900836 W KR9900836 W KR 9900836W WO 0041012 A1 WO0041012 A1 WO 0041012A1
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WO
WIPO (PCT)
Prior art keywords
light
bandwidth
filter
transmission
etalon
Prior art date
Application number
PCT/KR1999/000836
Other languages
French (fr)
Inventor
Keun-Woo Lee
Kil-Joo Chang
Jae-Seung Lee
Original Assignee
Lee Keun Woo
Chang Kil Joo
Lee Jae Seung
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Lee Keun Woo, Chang Kil Joo, Lee Jae Seung filed Critical Lee Keun Woo
Priority to JP2000592675A priority Critical patent/JP2002534707A/en
Priority to AU18953/00A priority patent/AU1895300A/en
Publication of WO2000041012A1 publication Critical patent/WO2000041012A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
    • G02B6/29358—Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
    • G02B6/29395—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device configurable, e.g. tunable or reconfigurable
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/106—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity
    • H01S3/1062—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating by controlling devices placed within the cavity using a controlled passive interferometer, e.g. a Fabry-Perot etalon

Definitions

  • the present inv ention relates in general to optical filters and, more particularly, to a bandwidth-v ariable optical filter that is capable of varying a transmission bandwidth continuously at any desired center wav elength by applying to the output light of a FP etalon, in which its light incidence angle can be adjusted an offset in the direction perpendicular to the output light
  • the present invention relates to an optical filter, which has a superior crosstalk characteristic because it can vary the shape of a transmission spectrum so as to obtain a Gaussian transmission characteristic
  • Fabry-Perot (FP) filters have been widely employed for allocating and monitoring WDM channels Howev ei since the transmission characteristic of such a conventional FP filter has a Lorentzian transmission curve that decreases very slowly, its channel crosstalk is large and its bandwidth is fixed
  • Bandwidth-variable optical filters are widely employed for the purpose of reducing channel crosstalk and Amplified Spontaneous Emission (ASE) Recently, there is proposed an angle-turned FP filter that can vary its optical bandwidth in a discrete way at a given center wavelength
  • the proposed FP filter can vary a channel bandwidth using the angular spread of an obliquely incident Gaussian beam, but cannot vary optical bandwidth continuously at an ⁇ desirable center wavelength because a center wavelength as well as a wavelength is varied when its incident angle is adjusted
  • an object of the present invention is to provide a bandwidth-variable optical filter that is capable of varying a transmission bandwidth continuously at any desired center wavelength by applying to the output light of a FP etalon, in which its light incidence angle can be adjusted, an offset in the direction perpendicular to an output light
  • the present invention provides a bandwidth-variable optical filter, comprising means for converting wavelength- division multiplexed incident light transmitted via an input optical fiber into parallel light, the light converting means being mounted to be rotatable so as to have its tilt angle, means for filtering the converted light by means of transmission or reflection of the light, and means for converging the filtered light having passed through the light filtering means to an output optical fiber, the light converging means being mounted to be movable in a direction perpendicular to a progress direction of the light
  • an optical signal having passed through an FP etalon whose incidence angle is adjustable is converged via a lens that is mounted to be movable in a x-direction perpendicular to the progress direction of the optical signal, thereby varying a transmission bandwidth continuously at any desired center wavelength and allowing a transmission spectrum to have a Gaussian characteristic, and, consequently, reducing the crosstalk between channels in WDM optical communication system
  • Fig 1 is a schematic diagram showing the construction of a bandwidth- variable optical filter in accordance with the present invention
  • Fig 2 is a schematic diagram showing an arrangement for testing the characteristics of the bandwidth-variable optical filter of the present invention
  • Figs 3 a to 3 f are graphs showing test results
  • Fig 1 is a view showing the construction of a bandwidth-variable optical filter in accordance with the present invention
  • reference numerals 1 1, 12 and 13 respectively designate a first lens, a FP etalon and a second lens
  • the bandwidth-variable optical filter of the present invention comprises the first lens 1 1 for converting incident light transmitted via an input optical fiber to parallel light, the FP etalon 12 for transmitting or reflecting the optical signal having passed through the first lens 1 1 depending on its wavelength, and the second lens 13 mounted to be movable in the direction perpendicular to the progress of the light for converging the light having passed through the FP etalon 12 to an output optical fiber
  • Incident light reaches the first lens 11 via the input optical fiber and, thereafter, is converted to parallel light in the process of passing through the first lens 1 1
  • the FP etalon 12 is formed by coating a dielectric mirror on both surfaces of a fused silica base plate that has a certain refractive index, is transparent, flat and of a uniform thickness
  • the FP etalon 12 is rotatably mounted so as to have a light incidence angle, that is to say, so as to adjust the incidence angle of light
  • a technique for rotatably mounting the FP etalon 12 so as to adjust the light incidence angle is well known, and so an explanation of this technique is omitted in this specification.
  • Parallel light that has passed through the first lens 1 1 reaches the FP etalon 12 at an incidence angle of 2.
  • This WDM parallel light is converted by the FP etalon 12 to multiple optical signals that respectively have certain channel bandwidths.
  • the second lens 13 which is positioned behind the FP etalon 12, exists on a z-axis if the progress direction of the incident light is designated as the z-axis, and converges the optical signal, which has passed through the FP etalon 12, to the output optical fiber.
  • the position of the second lens is fixed.
  • the second lens 13 is given varied offsets in the direction of the x-axis that is perpendicular to the progress direction of the incident light and the rotational axis of the FP etalon 12, thereby allowing the transmission bandwidth to be continuously varied while the center transmission wavelength of an entire filter is kept constant. That is, in the present invention, the second lens 13 is mounted to be movable in the direction of the x-axis. Since a technique for mounting the second lens 13 to be movable in the direction of the x-axis is well known, and so an explanation of this technique is omitted in this specification.
  • the bandwidth-variable optical filter of the present invention further comprises a plurality of lenses that are positioned behind the FP etalon 12, and serves to converge transmitted light.
  • this bandwidth-variable optical filter can converge effectively the optical signal that has passed through the FP etalon 12, so that the performance of the bandwidth-variable optical filter is improved still more.
  • the direction of the x-axis is perpendicular to the progress direction of the incident light and the rotational axis of the FP etalon 13.
  • the transmission bandwidth and shape of the transmission spectrum can be rendered to be varied within a certain range while the center transmission wavelength is hardly varied.
  • the incident light close to the center transmission wavelength experiences multiple reflections in the FP etalon 12 for a long time and, consequently, its transmission wave is widely distributed in the direction of x > 0 if the tilt angel 2 of the FP etalon 12 fulfills a condition of 2 > 0 Therefore, when 2 > 0 and )x is increased from 0, the wavelengths remote from the center transmission wavelength are not detected, and so the transmission spectrum assumes a periodic Gaussian curve
  • the transmission spectrum assumes a periodic Gaussian curve
  • the transmission spectrum becomes similar to the original, periodic Lorentzian curve Since the
  • Gaussian curve is abruptly decreased in size as it gets away from the center transmission wavelength, it can be employed in the manufacture of optical filters
  • Fig 2 is a schematic view showing an arrangement for testing the characteristics of the bandwidth-variable optical filter
  • a high power broadband light source there is used ASE of 5 8 dBm that is outputted from a first Erbium-Doped Fiber Amplifier (EDFA) 21
  • EDFA Erbium-Doped Fiber Amplifier
  • FPC Fiber Pigtailed Collimator
  • the ASE issued from the first Fiber Pigtailed Collimator (FPC) 22 is combined in free space and passes through the bandwidth-variable optical filter 23 Thereafter, the optical signal having passed through the bandwidth-variable optical filter 23 is recombined by means of a second FPC 24
  • the output spectrum of the optical signal, which is recombined by means of the second FPC 24, is measured using an optical spectrum analyzer 25
  • the diameter of the incident beam is 450 ⁇ m
  • the shape of the transmission spectrum can be varied by adjusting the incidence angel 2 of the beam and the offset ) ⁇ in the direction of the x-axis
  • the center wavelength of a transmission peak 8 p is about 1548 6 nm, and the bandwidth is varied discretely from 0 18 nm to 1 28 nm
  • the center wavelength is not varied abruptly, but the bandwidth is varied continuously as shown in Fig 3b
  • the test result shows that the bandwidth of the output transmission spectrum is varied by wavelength-dependent multiple reflections occurring in the FP etalon 12 Behind the FP etalon 12, when the wavelength gets close to 8 the intensive peak of the spectrum is widely distributed toward the positive direction of the x-axis Therefore, the transmission bandwidth is decreased along the positive direction of the x-axis but increased along the negative direction of the x-axis This coincides with the results obtained in experiments Therefore, as )x is larger than 0, the spectrum bandwidth of the
  • designates the output spectrum in a case where 2 15 2°
  • the bandwidth-variable optical filter of the present invention shows a Gaussian spectrum characteristic differently from a conventional FP filter
  • D designates the output spectrum in a case where
  • )x 0 ⁇ m
  • designates the output spectrum in a case where )x +100 ⁇ m
  • Fig 3d shows insertion losses measured with regard to the variations of 2 and )x When there is no FP etalon, the insertion loss is 0 65 dB When )x ⁇ - 200 ⁇ m, the insertion losses are increased However, in a case where )x > 0, or the conversion into a Gaussian characteristic in transmission characteristic occurs, the insertion losses are hardly decreased
  • the present invention provides a bandwidth-variable optical filter, which is capable of varying a transmission bandwidth continuously at any desired center wavelength and allowing transmission spectrum to have a Gaussian characteristic by applying an offset to the output of an FP etalon, thereby reducing the crosstalk between channels in WDM optical communication system.
  • the bandwidth-variable optical filter can be employed in the manufacture of Gaussian optical filters that respectively have narrow bandwidths. Since the bandwidth-variable optical filter has a variable bandwidth, it can be used for experimentally finding out the value of an optimum optical bandwidth in general optical experiments.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)
  • Spectrometry And Color Measurement (AREA)
  • Optical Filters (AREA)

Abstract

A bandwidth-variable optical filter is disclosed. The bandwidth-variable filter can continuously change a bandwidth of a transmission signal at any peak wavelength by providing vertical offsets with output signals of a Fabry-Pérot filter which controls launch angle. The bandwidth-variable filter comprises: a converter for converting a wavelength division multiplexed signal inputted through an optical fiber to a horizontal optical signal; a filter located as to rotate and have a slope, for filtering the wavelength division multiplexed horizontal signal; and a unit located vertically to a processing direction of the optical signal, for focusing transmission beam on the optical fiber in an output terminal.

Description

BAND WIDTH- VA 1 BLE OPTIC AL FILTER
Technical Field
The present inv ention relates in general to optical filters and, more particularly, to a bandwidth-v ariable optical filter that is capable of varying a transmission bandwidth continuously at any desired center wav elength by applying to the output light of a FP etalon, in which its light incidence angle can be adjusted an offset in the direction perpendicular to the output light
Background Art
In addition, the present invention relates to an optical filter, which has a superior crosstalk characteristic because it can vary the shape of a transmission spectrum so as to obtain a Gaussian transmission characteristic
In optical Wavelength-Division Multiplexed (WDM) communication systems, Fabry-Perot (FP) filters have been widely employed for allocating and monitoring WDM channels Howev ei since the transmission characteristic of such a conventional FP filter has a Lorentzian transmission curve that decreases very slowly, its channel crosstalk is large and its bandwidth is fixed
Bandwidth-variable optical filters are widely employed for the purpose of reducing channel crosstalk and Amplified Spontaneous Emission (ASE) Recently, there is proposed an angle-turned FP filter that can vary its optical bandwidth in a discrete way at a given center wavelength The proposed FP filter can vary a channel bandwidth using the angular spread of an obliquely incident Gaussian beam, but cannot vary optical bandwidth continuously at an\ desirable center wavelength because a center wavelength as well as a wavelength is varied when its incident angle is adjusted
Disclosure of the Invention Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a bandwidth-variable optical filter that is capable of varying a transmission bandwidth continuously at any desired center wavelength by applying to the output light of a FP etalon, in which its light incidence angle can be adjusted, an offset in the direction perpendicular to an output light
In order to accomplish the above object, the present invention provides a bandwidth-variable optical filter, comprising means for converting wavelength- division multiplexed incident light transmitted via an input optical fiber into parallel light, the light converting means being mounted to be rotatable so as to have its tilt angle, means for filtering the converted light by means of transmission or reflection of the light, and means for converging the filtered light having passed through the light filtering means to an output optical fiber, the light converging means being mounted to be movable in a direction perpendicular to a progress direction of the light
In accordance with the present invention, an optical signal having passed through an FP etalon whose incidence angle is adjustable is converged via a lens that is mounted to be movable in a x-direction perpendicular to the progress direction of the optical signal, thereby varying a transmission bandwidth continuously at any desired center wavelength and allowing a transmission spectrum to have a Gaussian characteristic, and, consequently, reducing the crosstalk between channels in WDM optical communication system
Brief Description of the Drawings
The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which
Fig 1 is a schematic diagram showing the construction of a bandwidth- variable optical filter in accordance with the present invention,
Fig 2 is a schematic diagram showing an arrangement for testing the characteristics of the bandwidth-variable optical filter of the present invention, and Figs 3 a to 3 f are graphs showing test results
Best Mode for Carrying Out the Invention
A preferred embodiment of the present invention is described with reference to the accompanying drawings, hereinafter
Fig 1 is a view showing the construction of a bandwidth-variable optical filter in accordance with the present invention In this drawing, reference numerals 1 1, 12 and 13 respectively designate a first lens, a FP etalon and a second lens
The bandwidth-variable optical filter of the present invention comprises the first lens 1 1 for converting incident light transmitted via an input optical fiber to parallel light, the FP etalon 12 for transmitting or reflecting the optical signal having passed through the first lens 1 1 depending on its wavelength, and the second lens 13 mounted to be movable in the direction perpendicular to the progress of the light for converging the light having passed through the FP etalon 12 to an output optical fiber
The operation of the bandwidth-variable optical filter of the present invention is as follows
Incident light reaches the first lens 11 via the input optical fiber and, thereafter, is converted to parallel light in the process of passing through the first lens 1 1 The FP etalon 12 is formed by coating a dielectric mirror on both surfaces of a fused silica base plate that has a certain refractive index, is transparent, flat and of a uniform thickness The FP etalon 12 is rotatably mounted so as to have a light incidence angle, that is to say, so as to adjust the incidence angle of light A technique for rotatably mounting the FP etalon 12 so as to adjust the light incidence angle is well known, and so an explanation of this technique is omitted in this specification.
Parallel light that has passed through the first lens 1 1 reaches the FP etalon 12 at an incidence angle of 2. This WDM parallel light is converted by the FP etalon 12 to multiple optical signals that respectively have certain channel bandwidths.
In the bandwidth-variable optical filter of the present invention, the second lens 13, which is positioned behind the FP etalon 12, exists on a z-axis if the progress direction of the incident light is designated as the z-axis, and converges the optical signal, which has passed through the FP etalon 12, to the output optical fiber. In the prior art, even when the FP filter is rotated, the position of the second lens is fixed.
In the bandwidth-variable optical filter of the present invention, the second lens 13 is given varied offsets in the direction of the x-axis that is perpendicular to the progress direction of the incident light and the rotational axis of the FP etalon 12, thereby allowing the transmission bandwidth to be continuously varied while the center transmission wavelength of an entire filter is kept constant. That is, in the present invention, the second lens 13 is mounted to be movable in the direction of the x-axis. Since a technique for mounting the second lens 13 to be movable in the direction of the x-axis is well known, and so an explanation of this technique is omitted in this specification.
Incidentally, besides these elements, the bandwidth-variable optical filter of the present invention further comprises a plurality of lenses that are positioned behind the FP etalon 12, and serves to converge transmitted light. When the bandwidth-variable optical filter of the present invention further comprises these lenses, this bandwidth-variable optical filter can converge effectively the optical signal that has passed through the FP etalon 12, so that the performance of the bandwidth-variable optical filter is improved still more.
The direction of the x-axis is perpendicular to the progress direction of the incident light and the rotational axis of the FP etalon 13. When )x, or an offset in the direction of the x-axis is varied, the transmission bandwidth and shape of the transmission spectrum can be rendered to be varied within a certain range while the center transmission wavelength is hardly varied The reason is because the incident light close to the center transmission wavelength experiences multiple reflections in the FP etalon 12 for a long time and, consequently, its transmission wave is widely distributed in the direction of x > 0 if the tilt angel 2 of the FP etalon 12 fulfills a condition of 2 > 0 Therefore, when 2 > 0 and )x is increased from 0, the wavelengths remote from the center transmission wavelength are not detected, and so the transmission spectrum assumes a periodic Gaussian curve On the other hand, when )x is in the vicinity of 0 or less than 0, the transmission spectrum becomes similar to the original, periodic Lorentzian curve Since the
Gaussian curve is abruptly decreased in size as it gets away from the center transmission wavelength, it can be employed in the manufacture of optical filters
Fig 2 is a schematic view showing an arrangement for testing the characteristics of the bandwidth-variable optical filter As a high power broadband light source, there is used ASE of 5 8 dBm that is outputted from a first Erbium-Doped Fiber Amplifier (EDFA) 21 The ASE issued from the first Fiber Pigtailed Collimator (FPC) 22 is combined in free space and passes through the bandwidth-variable optical filter 23 Thereafter, the optical signal having passed through the bandwidth-variable optical filter 23 is recombined by means of a second FPC 24 The output spectrum of the optical signal, which is recombined by means of the second FPC 24, is measured using an optical spectrum analyzer 25 In such a case, the diameter of the incident beam is 450 μm The shape of the transmission spectrum can be varied by adjusting the incidence angel 2 of the beam and the offset )\ in the direction of the x-axis The FP etalon 12 is made of fused silica having a refractive index of about 1 44 The mirror reflectivity of both surfaces and the thickness of the FP etalon 12 respectively are about 0 95 and about 150 μm
The output spectra obtained while the tilt angle 2 is varied in a state where )x = 0 are illustrated in Fig 3a The center wavelength of a transmission peak 8p is about 1548 6 nm, and the bandwidth is varied discretely from 0 18 nm to 1 28 nm When )x is varied within a range of ± 300 μm, the center wavelength is not varied abruptly, but the bandwidth is varied continuously as shown in Fig 3b In a case where 2 > 0, the test result shows that the bandwidth of the output transmission spectrum is varied by wavelength-dependent multiple reflections occurring in the FP etalon 12 Behind the FP etalon 12, when the wavelength gets close to 8 the intensive peak of the spectrum is widely distributed toward the positive direction of the x-axis Therefore, the transmission bandwidth is decreased along the positive direction of the x-axis but increased along the negative direction of the x-axis This coincides with the results obtained in experiments Therefore, as )x is larger than 0, the spectrum bandwidth of the
ASE that is transmitted by the etalon filter is decreased The intensity peak is hardly affected by )x On the other hand, as )x is smaller than 0, the spectrum bandwidth of the ASE is increased However, in the vicinity of an area where )x = 0 and which deviates from the distribution area of the incident beam, loss is increased largely
In the graph of Fig 3 a, D designates the output spectrum in a case where 2 = 0°, * designates the output spectrum in a case where 2 = 6 9°, Δ designates the output spectrum in a case where 2 = 9 9°, designates the output spectrum in a case where 2 = 15 2°, V designates the output spectrum in a case where 2 = 18 9°, x designates the output spectrum in a case where 2 = 23 4°, and 0 designates the output spectrum in a case where 2 = 32°
In the graph of Fig 3b, I designates the bandwidth in a case where 2 = 0°, I designates the bandwidth in a case where 2 = 6 9°, * designates the bandwidth in a case where 2 = 9 9°, A designates the bandwidth in a case where 2 = 15 2°, x designates the bandwidth in a case where 2 = 18 9°, T designates the bandwidth in a case where 2 = 23 4°, and ♦ designates the bandwidth in a case where 2 = 32°
Fig 3 c illustrates transmission spectra while the FP etalon 12 is moved in a state where 2 = 6 9° When the FP etalon 12 is moved in a positive direction of the x-axis, the components whose wavelengths are close to 8p are predominant Therefore, when )x > 0, it can be known that the bandwidth-variable optical filter of the present invention shows a Gaussian spectrum characteristic differently from a conventional FP filter In the graph of Fig 3 c, D designates the output spectrum in a case where
)x = 0 μm, * designates the output spectrum in a case where )x = +300 μm, A designates the output spectrum in a case where )x = +200 μm, designates the output spectrum in a case where )x = +100 μm, T designates the output spectrum in a case where )x = -100 μm, 0 designates the output spectrum in a case where )x = -200 μm, and + designates the output spectrum in a case where )x = -300 μm
Fig 3d shows insertion losses measured with regard to the variations of 2 and )x When there is no FP etalon, the insertion loss is 0 65 dB When )x < - 200 μm, the insertion losses are increased However, in a case where )x > 0, or the conversion into a Gaussian characteristic in transmission characteristic occurs, the insertion losses are hardly decreased
In the graph of Fig 3d, I designates the attenuation in a case where 2 = 0°, I designates the attenuation in a case where 2 = 6 9°, * designates the attenuation in a case where 2 = 9 9°, A designates the attenuation in a case where 2 = 15.2°, x designates the attenuation in a case where 2 = 18.9°, T designates the attenuation in a case where 2 = 23 4°, and ♦ designates the attenuation in a case where 2 = 32°
Fig 3e and Fig 3 f respectively show the output spectra in cases where )x = 0 and +300 μm when 2 = 6 9°
Industrial Applicability
As described above, the present invention provides a bandwidth-variable optical filter, which is capable of varying a transmission bandwidth continuously at any desired center wavelength and allowing transmission spectrum to have a Gaussian characteristic by applying an offset to the output of an FP etalon, thereby reducing the crosstalk between channels in WDM optical communication system. Additionally, the bandwidth-variable optical filter can be employed in the manufacture of Gaussian optical filters that respectively have narrow bandwidths. Since the bandwidth-variable optical filter has a variable bandwidth, it can be used for experimentally finding out the value of an optimum optical bandwidth in general optical experiments.

Claims

Claims
1 A bandwidth-variable optical filter, comprising means for converting wavelength-division multiplexed incident light transmitted via an input optical fiber into parallel light, said light converting means being mounted to be rotatable so as to have its tilt angle, means for filtering the converted light by means of transmission or reflection of the light, and means for converging the filtered light having passed through said light filtering means to an output optical fiber, said light converging means being mounted to be movable in a direction perpendicular to a progress direction of the light
2 The filter according to claim 1, wherein said light converging means includes one or more lenses
3 The filter according to claim 1 or 2, wherein said light filtering means includes a rotatably mounted Fabry-Perot etalon
4 The filter according to claim 3, wherein said Fabry-Perot etalon is mounted to adjust its tilt angle and said light converging means is mounted to adjust its offset in the perpendicular direction, so that a transmission spectrum bandwidth of the light may be varied continuously and a shape of the transmission spectrum of the light may be varied between a Lorentzian curve and a Gaussian curve
PCT/KR1999/000836 1998-12-30 1999-12-30 Bandwidth-variable optical filter WO2000041012A1 (en)

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Application Number Priority Date Filing Date Title
JP2000592675A JP2002534707A (en) 1998-12-30 1999-12-30 Variable bandwidth optical filter
AU18953/00A AU1895300A (en) 1998-12-30 1999-12-30 Bandwidth-variable optical filter

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KR1998/62145 1998-12-30
KR1019980062145A KR100314890B1 (en) 1998-12-30 1998-12-30 Bandwidth variable optical filter

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WO2002052306A2 (en) * 2000-11-03 2002-07-04 Optune Technologies Band pass interferometer with tuning capabilities
CN103196569A (en) * 2013-04-22 2013-07-10 哈尔滨工业大学（威海） Method for measuring laser wavelength by rotating Fabry-Perot interferoscope

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Cited By (4)

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WO2002052306A2 (en) * 2000-11-03 2002-07-04 Optune Technologies Band pass interferometer with tuning capabilities
WO2002052306A3 (en) * 2000-11-03 2002-10-31 Optune Technologies Band pass interferometer with tuning capabilities
US7002696B1 (en) 2000-11-03 2006-02-21 Optune Technologies Band pass interferometer with tuning capabilities
CN103196569A (en) * 2013-04-22 2013-07-10 哈尔滨工业大学（威海） Method for measuring laser wavelength by rotating Fabry-Perot interferoscope

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