Variable optical attenuator with tunable wavelength selectivity

Abstract

A variable optical attenuator with tunable wavelength selectivity includes at least two reflectors disposed parallel to each other at a predetermined angle from an optic axis and driving units connected to said at least two reflectors for allowing the reflectors to move back and forth in a direction perpendicular or parallel to the optic axis or to revolve centering on an axis perpendicular or parallel to the optic axis. Since the variable optical attenuator of the present invention serves as a variable optical attenuator and, at the same time, as a tunable wavelength filter, problems of insertion loss and optical alignment that might be caused by separately installing a variable optical attenuator and a wavelength filter can be effectively prevented. Moreover, by implementing the variable optical attenuator and the tunable wavelength filter by using a single device, the size of a system using the optical attenuator can be reduced.

1 - 13 . (canceled)  
   
   
       14 . A variable optical attenuator with tunable wavelength selectivity comprising: 
 at least two reflectors disposed parallel to each other to form a Fabry-Perot cavity, wherein the Fabry-Perot cavity overlaps with an optical path at a transmission area, and;    driving units connected to said at least two reflectors for allowing transmitted power to change with a variation of the overlapped area between the Fabry-Perot cavity and the optical path.    
   
   
       15 . The attenuator of  claim 14 , wherein light having a resonant wavelength satisfying a resonance condition is transmitted through the transmission area while light having a non-resonant wavelength not satisfying the resonance condition is reflected at the transmission area, and the resonant wavelength satisfying the resonance condition is varied as the reflectors are moved back and forth in a direction parallel to an optic axis or revolved centering on an axis perpendicular to the optic axis by the driving units.  
   
   
       16 . The attenuator of  claim 14 , wherein the transmission area is varied as the reflectors are moved back and forth in a direction perpendicular to the optic axis or revolved centering on an axis parallel to the optic axis by the driving units.  
   
   
       17 . The attenuator of  claim 14 , wherein the attenuator transmits the light having the resonant wavelength satisfying the resonance condition if the transmission area covers whole cross-section of the optical path but reflects all of incident light if the transmission area does not exist.  
   
   
       18 . The attenuator of  claim 14 , wherein angles between the reflectors and the optic axis are changed in a predetermined degree from 90° in order to prevent the light having a non-resonant wavelength from being reflected back to an input optical waveguide or an optical fiber.  
   
   
       19 . The attenuator of  claim 14 , wherein angles between the reflectors and the optic axis are changed in a predetermined degree from 90° in order to prevent an additional Fabry-Perot cavity from being formed between a reflector and an optical waveguide or an optical fiber.  
   
   
       20 . The attenuator of  claim 14 , wherein at least one of the reflectors are a distributed Bragg reflector (DBR) or have a 2- or 3-dimensional photonic crystal structure.  
   
   
       21 . The attenuator of  claim 14 , wherein each of the reflectors is made of a metal film, a dielectric film, an organic film, a semiconductor film, a combination thereof, or a combination of these films and an air gap.  
   
   
       22 . The attenuator of  claim 14 , wherein at least one of the reflectors have a 1- or 2-dimensional lens-shaped surface or an additional 1- or 2-dimensioanl lens-shaped surface structure is inserted between the optical fiber and the reflector.  
   
   
       23 . The attenuator of  claim 14 , wherein end portions of the reflectors may have a shape selected from a line, a curve, and a polygon.  
   
   
       24 . The attenuator of  claim 14 , wherein at least one of the reflectors has a reflectance which is changed by using a heat, a current, a voltage, light, an electromagnetic wave or a pressure.  
   
   
       25 . The attenuator of  claim 14 , wherein at least one of the reflectors is fixed at a certain position while the other reflectors are moved back and forth or revolved.  
   
   
       26 . The attenuator of  claim 14 , wherein the driving units drive the reflectors to move back and forth or to revolve by employing a heat, a current, an electromagnetic force, an electrostatic force or a piezoelectric force.  
   
   
       27 . A variable optical attenuator, comprising: 
 at least two reflectors disposed parallel to each other at a predetermined angle from an optic axis; and    driving units connected to said at least two reflectors for allowing the reflectors to move back and forth in a direction perpendicular or parallel to the optic axis or to revolve centering on an axis perpendicular or parallel to the optic axis,    wherein the variable optical attenuator is a variable optical attenuator with tunable wavelength selectivity and is installed between optical waveguides or optical fibers.    
   
   
       28 . The attenuator of  claim 27 , wherein a Fabry-Perot cavity overlaps with an optical path at a transmission area, light having a resonant wavelength satisfying a resonance condition is transmitted through the transmission area while light having a non-resonant wavelength not satisfying the resonance condition is reflected at the transmission area, and the resonance condition is dependant on a distance between the reflectors.  
   
   
       29 . The attenuator of  claim 28 , wherein the resonant wavelength satisfying the resonance condition is varied as the reflectors are moved back and forth in a direction parallel to the optic axis or revolved centering on an axis perpendicular to the optic axis by the driving units.  
   
   
       30 . The attenuator of  claim 28 , wherein the transmission area is varied as the reflectors are moved back and forth in a direction perpendicular to the optic axis or revolved centering on an axis parallel to the optic axis, and transmitted power is changed with a variation of the transmission area.  
   
   
       31 . The attenuator of  claim 28 , wherein the attenuator transmits the light having the resonant wavelength satisfying the resonance condition if the transmission area covers whole cross-section of the optical path but reflects all of incident light if the transmission area does not exist.  
   
   
       32 . The attenuator of  claim 27 , wherein at least one of the reflectors are a distributed Bragg reflector (DBR) or have a 2- or 3-dimensional photonic crystal structure.  
   
   
       33 . The attenuator of  claim 27 , wherein each of the reflectors is made of a metal film, a dielectric film, an organic film, a semiconductor film, a combination thereof, or a combination of these films and an air gap.  
   
   
       34 . The attenuator of  claim 27 , wherein at least one of the reflectors have a 1- or 2-dimensional lens-shaped surface or an additional 1- or 2-dimensioanl lens-shaped surface structure is inserted between the optical fiber and the reflector.  
   
   
       35 . The attenuator of  claim 27 , wherein end portions of the reflectors may have a shape selected from a line, a curve, and a polygon.  
   
   
       36 . The attenuator of  claim 27 , wherein at least one of the reflectors has a reflectance which is changed by using a heat, a current, a voltage, light, an electromagnetic wave or a pressure.  
   
   
       37 . The attenuator of  claim 27 , wherein at least one of the reflectors is fixed at a certain position while the other reflectors are moved back and forth or revolved.  
   
   
       38 . The attenuator of  claim 27 , wherein angles between the reflectors and the optic axis are changed in a predetermined degree from 90° in order to send reflected light in a specific direction.  
   
   
       39 . The attenuator of  claim 27 , wherein the driving units drive the reflectors to move back and forth or to revolve by employing a heat, a current, an electromagnetic force, an electrostatic force or a piezoelectric force.