WO2003104881A1 - 可変光学フィルタ - Google Patents
可変光学フィルタ Download PDFInfo
- Publication number
- WO2003104881A1 WO2003104881A1 PCT/JP2003/007279 JP0307279W WO03104881A1 WO 2003104881 A1 WO2003104881 A1 WO 2003104881A1 JP 0307279 W JP0307279 W JP 0307279W WO 03104881 A1 WO03104881 A1 WO 03104881A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- phase difference
- polarizer
- variable
- wavelength
- optical axis
- Prior art date
Links
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/09—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour based on magneto-optical elements, e.g. exhibiting Faraday effect
-
- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F2203/00—Function characteristic
- G02F2203/05—Function characteristic wavelength dependent
- G02F2203/055—Function characteristic wavelength dependent wavelength filtering
Definitions
- the present invention relates to a variable optical finoletor used in an optical communication system and the like. More specifically, a phase difference element is arranged before and after a variable Faraday rotator in an optical path, and the optical axes of two phase difference elements are set in different directions. It relates to a variable optical filter with improved non-linearity (linearity when logarithmic transmittance is displayed) over a wide operating tilt range by setting. Background art
- one or more optical amplifiers such as an erbium-doped fiber amplifier (EDFA) are incorporated in each repeater, and long-distance transmission is performed by amplifying the attenuated signal. .
- EDFA erbium-doped fiber amplifier
- the amplification wavelength characteristics of the EDFA affect communication quality.
- the wavelength characteristics of each EDFA are corrected by a fixed optical gain equalizer for each EDFA, but the wavelength characteristics will be inclined due to aging or fluctuations in the input signal light. For multiple cascaded EDFAs, the accumulation of this slope degrades the optical signal-to-noise of the lossy channel. To correct this tilt, a variable optical filter is used.
- variable optical filter having a structure in which a first polarizer, a phase difference element, a variable Faraday rotator, and a second polarizer are arranged in this order along an optical axis (Japanese Patent Laid-Open No. -212044).
- the transmittance has the rotation angle wavelength dependence of the variable Faraday rotator, and the wavelength characteristic of the phase difference element changes in a trigonometric function.
- the slope of an EDFA is expressed by the logarithm of the wavelength characteristic. It is known that when displayed, it changes so as to follow a straight line, and it is required to compensate for this as accurately as possible. However, conventional techniques are not always sufficient. Disclosure of the invention
- An object of the present invention is to provide a tunable optical filter capable of improving linearity when a loss wavelength characteristic is expressed in logarithm over a given wide operating bandwidth. It is another object of the present invention to provide a tunable optical filter capable of reducing variation in average insertion loss over a given wide operating bandwidth.
- One embodiment of the present invention provides a first polarizer, a first phase difference element for generating a phase difference, a variable Faraday rotator for performing variable Faraday rotation, and a second phase for generating a phase difference.
- another embodiment of the present invention provides a first polarizer, a first phase difference element for generating a phase difference, a variable Faraday rotator for performing variable Faraday rotation, and a second phase for generating a phase difference.
- the rotation direction of the angle ⁇ is positive
- the angle ⁇ formed by the polarization transmission direction of the second polarizer with respect to the polarization transmission direction of the first polarizer is ⁇ >
- the optical axis of the first phase difference element is the transmitting polarization azimuth and angle of the first polarizer ( ⁇ ⁇ 0, Ri optic axis of the second retardation element is transmitted polarization azimuth and angle phi 2 of the first polarizer phi 2 ⁇ 0 der ,
- FIG. 1 is an explanatory diagram showing a basic configuration of a variable optical filter according to the present invention
- FIG. 2 is an explanatory diagram showing the relationship between the transmission polarization direction and the optical axis
- FIG. 3 is a configuration diagram of the present invention
- FIG. 4 is a graph showing an example of the loss wavelength characteristic according to the present invention.
- FIG. 5 is a graph showing the linearity of the loss wavelength characteristic according to the present invention.
- FIG. 6 is a graph showing the relationship between the loss slope and the average insertion loss according to the present invention.
- FIG. 7 is a graph showing the relationship between wavelength tilt and linearity according to the present invention.
- FIG. 8 is a graph showing the relationship between the Faraday rotation angle and the wavelength tilt according to the present invention
- FIG. 9 is a configuration diagram of the prior art
- FIG. 10 is a graph showing an example of a loss wavelength characteristic according to the related art.
- Figure 11 is a graph showing the linearity of the loss wavelength characteristic according to the prior art.
- FIG. 12 is a graph showing the relationship between the loss slope and the average insertion loss according to the prior art.
- FIG. 1 shows the basic configuration of the variable optical filter according to the present invention.
- the variable optical filter includes a first polarizer 10, a first phase difference element 12 for generating a phase difference, a variable Faraday rotator 14 for providing a variable Faraday rotation, and a second Faraday rotator 14 for generating a phase difference.
- the phase difference element 16 and the second polarizer 18 are arranged along the optical axis in that order.
- FIG. 2 when the optical axes of the first and second phase difference elements and transmitting polarization azimuth and angle of the first polarizer, and a phi ⁇ Pi phi 2 respectively, ⁇ and [Phi 2 And the different angles (That is, set to ( ⁇ ⁇ ⁇ ⁇ .
- the second direction with respect to the polarization transmission direction of the first polarizer is The angle ⁇ formed by the polarization transmission direction of the polarizer of ⁇ is ⁇ > 0, the angle formed by the optical axis of the first phase difference element with the transmission polarization direction of the first polarizer ⁇ i is ⁇ ⁇ 0, and the second phase difference The angle ⁇ 2 between the optical axis of the element and the transmitted polarization direction of the first polarizer is ⁇ 2 ⁇ 0.
- the directions of cancellation are opposite, so the phase difference elements are arranged before and after the variable Faraday rotator, and the angle formed by the optical axis differs in each case. To do.
- phase differences generated by the first and second phase difference elements are ⁇ i and ⁇ 2 , at least one of them is (2 n + 1) ⁇ / 4 ( Where ⁇ is any wavelength within the given transmission band).
- a preferred example is the center wavelength of a given transmission band.
- the phase difference ⁇ of the first phase difference element is 13/4 ⁇ 9 ⁇ 4 ⁇ .
- the phase difference delta 2 of the second phase Samoto child is 1 3/4 lambda. ⁇ 2 ⁇ 49 4 ⁇ .
- the variation of the average insertion loss at a wavelength slope of 5 dB to +5 dB at a transmission bandwidth of 4 Onm is 0.5 dB or less.
- phase difference ⁇ of the first phase difference element is 1 3/4 ⁇ . ⁇ ⁇ 9 ⁇ 4 ⁇ .
- phase difference ⁇ 2 of the second phase difference element is 13 / 4 ⁇ . ⁇ ⁇ 2 ⁇ 4 9/4 ⁇ .
- There is a variable optical filter having a transmission bandwidth of 4 Onm and a linearity of a loss wavelength characteristic in a wavelength inclination of 5 dB to +5 dB less than 0.2 dB.
- the phase difference ⁇ of the first phase difference element becomes ⁇ ⁇ / ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 4 9/4 ⁇ .
- a phase difference delta 2 of the second phase difference element 1 3/4 ⁇ ⁇ 2 ⁇ 49/4 ⁇ , the transmission bandwidth 4 loss wavelength in the wavelength tilt one 5 d B ⁇ + 5 d B at Onm
- There is a variable optical filter having a characteristic linearity of 0.2 dB or less and a variable inclination range of 16.5 dB to +6.5 dB.
- phase Sa ⁇ and delta 2 range in example combinations linear 1-raw when the transmittance shown logarithmic table is very good, when determined from the results of the simulated Chillon under different conditions It was obtained as a necessary condition.
- phase difference ⁇ Pi delta 2 phi There phi 2, S
- first magnetic field applying means for magnetically saturating the magneto-optical crystal, and non-parallel to the applied magnetic field direction of the first magnetic field applying means
- second magnetic field applying means for applying a variable magnetic field in various directions.
- the first and second polarizers are wedge plates made of a birefringent material, and are disposed so that their tops and bottoms are opposite to each other. A configuration having a flat plate shape is also possible.
- the first polarizer it is preferable to combine the first polarizer so that the optical axis direction of the first phase difference element is orthogonal to the optical axis direction of the first polarizer when viewed in the optical axis direction.
- the materials of the first and second retardation elements are changed so that the temperature characteristics of the refractive index changes have opposite signs. Then, the temperature characteristics as a whole can be improved.
- the first and second phase difference element for example a crystal, vanadate Germany thorium (YV_ ⁇ 4), lead molybdate (P BMo0 4), rutile (T i 0 2), etc. can be used.
- Bi-substituted rare earth iron garnet was used for the magneto-optical crystal of the variable Faraday rotator, and quartz was used for the first and second phase difference elements.
- the direction of rotation of polarized light is positive in the counterclockwise direction (therefore, the direction of rotation of the Faraday rotator at a rotation angle of 0 is also positive).
- the optical axis of the second phase difference element is the transmission polarization direction of the first polarizer.
- the phase difference ⁇ of the first phase difference element is 33 / 4 ⁇ .
- Figure 5 shows the loss deviation (deviation from linearity).
- FIGS. 4 and 5 which show the loss wavelength characteristics, the linearity is maintained even when the slope (defined by the loss difference at both ends of the wavelength) increases.
- series 1 to 5 correspond to different Faraday rotation angles, and the slopes are +5 dB, +2.5 dB, 0 dB, one 2.5 dB, one It corresponds to 5 dB.
- the linearity of the loss wavelength characteristics is evaluated by the difference between the straight line connecting the loss values at both ends of the wavelength at each slope and the loss at each wavelength.
- a linearity of ⁇ 0.2 dB is realized in a tilt range of +5 dB to 1-5 dB.
- the linearity is from +0.2 dB to 10.6 dB in the same range as shown in FIGS. 10 and 11.
- FIG. Figure 6 shows an example of one loss slope.
- the average insertion loss is the average of the loss values at each wavelength.
- the variation of the average input loss is 0.3 dB in the slope range of 15 dB to 15 dB, and the variation of the average input loss in the conventional technology (0.5 dB in Fig. 12). ).
- FIG. 7 shows an example of the wavelength gradient linearity (linearity-one wavelength gradient) in the configuration of the present invention shown in FIG.
- the linearity is the linearity when the loss wavelength characteristic is expressed in logarithm.
- FIG. 8 shows the relationship between the Faraday rotation angle and the wavelength tilt obtained under the same conditions as those for obtaining FIG.
- the advantage is that the wavelength tilt can be continuously changed by changing the rotation angle.
- the front of the variable Faraday rotator in the optical path Since the phase difference element is arranged later and the optical axes of the two phase difference elements are set to different directions, the non-linearity (linearity when logarithmic transmittance is displayed) in a wide operation inclination range is good. ( ⁇ 0.2 dB) variable optical filter is obtained.
- the controllable wavelength range is expanded, and the signal light range can be used in a wider wavelength range, resulting in large-capacity transmission.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP03736103.7A EP1515180B1 (en) | 2002-06-10 | 2003-06-09 | Variable optical filter |
US11/009,991 US7050216B2 (en) | 2002-06-10 | 2004-12-10 | Variable optical filter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2002169028A JP4156280B2 (ja) | 2002-06-10 | 2002-06-10 | 可変光学フィルタ |
JP2002-169028 | 2002-06-10 |
Related Child Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US11/009,991 Continuation US7050216B2 (en) | 2002-06-10 | 2004-12-10 | Variable optical filter |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2003104881A1 true WO2003104881A1 (ja) | 2003-12-18 |
Family
ID=29727713
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2003/007279 WO2003104881A1 (ja) | 2002-06-10 | 2003-06-09 | 可変光学フィルタ |
Country Status (4)
Country | Link |
---|---|
US (1) | US7050216B2 (ja) |
EP (1) | EP1515180B1 (ja) |
JP (1) | JP4156280B2 (ja) |
WO (1) | WO2003104881A1 (ja) |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH06130339A (ja) * | 1992-10-16 | 1994-05-13 | Fujitsu Ltd | チューナブル光学フィルタ |
JPH11212044A (ja) | 1998-01-23 | 1999-08-06 | Fujitsu Ltd | 可変光学フィルタ |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2003121807A (ja) * | 2001-10-12 | 2003-04-23 | Fujitsu Ltd | 可変偏光面回転子およびそれを用いた光デバイス |
-
2002
- 2002-06-10 JP JP2002169028A patent/JP4156280B2/ja not_active Expired - Fee Related
-
2003
- 2003-06-09 WO PCT/JP2003/007279 patent/WO2003104881A1/ja active Application Filing
- 2003-06-09 EP EP03736103.7A patent/EP1515180B1/en not_active Expired - Lifetime
-
2004
- 2004-12-10 US US11/009,991 patent/US7050216B2/en not_active Expired - Fee Related
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH06130339A (ja) * | 1992-10-16 | 1994-05-13 | Fujitsu Ltd | チューナブル光学フィルタ |
JPH11212044A (ja) | 1998-01-23 | 1999-08-06 | Fujitsu Ltd | 可変光学フィルタ |
Non-Patent Citations (1)
Title |
---|
See also references of EP1515180A4 * |
Also Published As
Publication number | Publication date |
---|---|
US20050134954A1 (en) | 2005-06-23 |
JP4156280B2 (ja) | 2008-09-24 |
EP1515180A1 (en) | 2005-03-16 |
US7050216B2 (en) | 2006-05-23 |
EP1515180B1 (en) | 2015-08-12 |
JP2004013008A (ja) | 2004-01-15 |
EP1515180A4 (en) | 2008-07-02 |
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