WO2004019087A2 - A variable optical attenuator - Google Patents

A variable optical attenuator Download PDF

Info

Publication number
WO2004019087A2
WO2004019087A2 PCT/GB2003/003611 GB0303611W WO2004019087A2 WO 2004019087 A2 WO2004019087 A2 WO 2004019087A2 GB 0303611 W GB0303611 W GB 0303611W WO 2004019087 A2 WO2004019087 A2 WO 2004019087A2
Authority
WO
WIPO (PCT)
Prior art keywords
lightguide
end wall
channel
variable optical
optical attenuator
Prior art date
Application number
PCT/GB2003/003611
Other languages
French (fr)
Other versions
WO2004019087A3 (en
Inventor
Harm Van Weerden
Hindrick Freerk Bulthuis
Mark Lawrence Begbie
Remco Stoffer
Original Assignee
Avanex Uk Limited
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 Avanex Uk Limited filed Critical Avanex Uk Limited
Publication of WO2004019087A2 publication Critical patent/WO2004019087A2/en
Publication of WO2004019087A3 publication Critical patent/WO2004019087A3/en

Links

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
    • G02B6/35—Optical coupling means having switching means
    • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
    • G02B6/3512—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror
    • G02B6/352—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being reflective, e.g. mirror the reflective optical element having a shaped reflective surface, e.g. a reflective element comprising several reflective surfaces or facets that function together
    • 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
    • G02B6/264—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting
    • G02B6/266—Optical coupling means with optical elements between opposed fibre ends which perform a function other than beam splitting the optical element being an attenuator
    • 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
    • G02B6/35—Optical coupling means having switching means
    • G02B6/351—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements
    • G02B6/353—Optical coupling means having switching means involving stationary waveguides with moving interposed optical elements the optical element being a shutter, baffle, beam dump or opaque element
    • 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
    • G02B6/35—Optical coupling means having switching means
    • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
    • G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
    • G02B6/3548—1xN switch, i.e. one input and a selectable single output of N possible outputs
    • G02B6/355—1x2 switch, i.e. one input and a selectable single output of two possible outputs
    • 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
    • G02B6/35—Optical coupling means having switching means
    • G02B6/354—Switching arrangements, i.e. number of input/output ports and interconnection types
    • G02B6/3544—2D constellations, i.e. with switching elements and switched beams located in a plane
    • G02B6/3548—1xN switch, i.e. one input and a selectable single output of N possible outputs
    • G02B6/3552—1x1 switch, e.g. on/off switch
    • 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
    • G02B6/35—Optical coupling means having switching means
    • G02B6/3594—Characterised by additional functional means, e.g. means for variably attenuating or branching or means for switching differently polarized beams
    • 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
    • G02B6/35—Optical coupling means having switching means
    • G02B6/3596—With planar waveguide arrangement, i.e. in a substrate, regardless if actuating mechanism is outside the substrate
    • 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
    • G02B6/36—Mechanical coupling means
    • G02B6/38—Mechanical coupling means having fibre to fibre mating means
    • G02B6/3807—Dismountable connectors, i.e. comprising plugs
    • G02B6/381—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres
    • G02B6/3818—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres of a low-reflection-loss type
    • 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
    • G02B6/36—Mechanical coupling means
    • G02B6/38—Mechanical coupling means having fibre to fibre mating means
    • G02B6/3807—Dismountable connectors, i.e. comprising plugs
    • G02B6/381—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres
    • G02B6/3818—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres of a low-reflection-loss type
    • G02B6/382—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres of a low-reflection-loss type with index-matching medium between light guides
    • 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
    • G02B6/36—Mechanical coupling means
    • G02B6/38—Mechanical coupling means having fibre to fibre mating means
    • G02B6/3807—Dismountable connectors, i.e. comprising plugs
    • G02B6/381—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres
    • G02B6/3818—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres of a low-reflection-loss type
    • G02B6/3822—Dismountable connectors, i.e. comprising plugs of the ferrule type, e.g. fibre ends embedded in ferrules, connecting a pair of fibres of a low-reflection-loss type with beveled fibre ends

Definitions

  • the present invention relates to variable optical attenuators and optical switches. More particularly, but not exclusively, the present invention relates to a variable optical attenuator having a channel for receiving a shutter, the channel being generally wedged shaped with one wall inclined to the other.
  • Known optical attenuators typically comprise first and second co-axial lightguides.
  • the lightguides are separated by a channel substantially normal to the lightguides.
  • a shutter is adapted to be displaced within the channels to attenuate light passing across the channel between the lightguides.
  • the opposite sides of the channel are parallel and for reliability purposes the channel is filled with air.
  • the higher refractive index difference between the lightguide and air results in considerable reflection at these sides of the channel. Due to repeated reflection of light from the opposite sides of the channel, the channel acts as a Fabry Perot resonator, causing considerable variation in wavelength dependent loss in the transmission response for the optical attenuator .
  • the present invention seeks to overcome the disadvantage of known optical attenuators.
  • a variable optical attenuator comprising: a first lightguide having a first end wall; a second lightguide having a second end wall arranged to directly receive light emitted from the first end wall ; the first and second end walls defining a channel for receiving a shutter; wherein at least a portion of the second end wall is inclined to the first end wall.
  • variable optical attenuator can be an optical switch.
  • the first and second lightguides are arranged in a substrate, the first and second end walls being perpendicular to the substrate.
  • the optical axis of the first and second lightguides can be co-axial.
  • the optical axis of the first lightguide is parallel to but displaced from the optical axis of the second lightguide.
  • the optical axis of the second lightguide is inclined to the optical axis of the first lightguide, reducing the insertion loss .
  • At least one of the first and second end walls is inclined to the optical axis of the respective lightguide proximate to the end wall, again reducing the insertion loss.
  • the channel can contain an index matching fluid, particularly an index matching oil.
  • an optical switch comprising: a first lightguide having a first end wall; a second lightguide having a second end wall arranged to directly receive light emitted from the first end wall; the first and second end walls defining a channel for receiving a mirror; a third lightguide having one end arranged to directly receive light reflected from the mirror; wherein at least a portion of the second end wall is inclined to the first end wall.
  • Figure 1 shows a known variable optical attenuator
  • Figure 2 shows a variable optical attenuator according to the invention
  • Figure 3 shows a further embodiment of a variable optical attenuator according to the invention.
  • Figure 4 shows a further embodiment of a variable optical attenuator according to the invention.
  • Figures 5 and 6 show the results of numerical calculations of the insertion loss and return loss for a known variable optical attenuator and an attenuator according to the invention
  • Figure 7 shows measured insertion loss as a function of wavelength for a known parallel slot variable optical attenuator
  • Figure 8 shows measured insertion loss as a function of wavelength for a wedge slot variable optical attenuator according to the invention
  • Figure 9 shows a variable optical attenuator according to the invention including a shutter
  • Figure 10 shows a further embodiment of a variable optical attenuator according to the invention including a shutter
  • Figure 11 shows a switch according to a further embodiment of the invention.
  • FIG. 1 Shown in Figure 1 is a known variable optical attenuator comprising first and second lightguides 1, 2 within a substrate 3.
  • An air filled parallel channel 4 separates the first and second lightguides 1,2.
  • a shutter (not shown) is adapted to be displaced within the channel 4 to attenuate the beam.
  • Fig.l shows the "through-state" in which the shutter is not attenuating the beam.
  • a lightbeam is transmitted along the first lightguide 1.
  • the beam exits the lightguide 1 at a first end wall 5 and is transmitted across the air filled channel 4 to the second end wall 6 of the second lightguide 2.
  • a portion of the light beam is transmitted into the second lightguide 2.
  • due to the difference in refractive index between the air filled channel 4 and the lightguides 1,2 a portion of the beam is reflected as shown.
  • the reflected beam returns towards the first lightguide 1 where it is again partially reflected/transmitted.
  • Multiple reflections between the opposite walls of the channel 4 cause the channel 4 to act as Fabry Perot interferometer causing a substantial wavelength dependent loss in the attenuator.
  • the channel 4 can be inclined with respect to the normal to the lightguides 1,2. This causes the reflected beams to be displaced with respect to the beam. This reduces the number of reflected beams received by the lightguide 1, 2 as shown, so reducing the wavelength dependent loss. However, the wavelength dependent loss is still considered to be too high for many applications.
  • FIG. 2 Shown in Figure 2 is a variable optical attenuator according to the invention.
  • the attenuator comprises first and second lightguides 1,2 received within a substrate 3.
  • First and second lightguide end walls 5,6 define an air filled channel 4 for receiving the shutter (not shown) .
  • the first and second end walls 5,6 are inclined to their respective lightguides 1,2, so inclining the channel 4 to the lightguides 1,2 as can be seen.
  • the end walls 5,6 are not parallel, the second end wall 6 is inclined to the first 5 to produce a wedge shaped channel 4.
  • the inclination of the second end wall 6 to the first end wall 5 is the slot angle.
  • the channel 4 extends into the substrate 3 as shown.
  • the non-parallel end faces 5,6 increase the off-set of the reflected beam with respect to the first end face 5 (by comparison with Figure 1) . This suppresses the Fabry Perot effect.
  • FIG. 3 A further embodiment of a variable optical attenuator according to the invention is shown in Figure 3.
  • the optical axis of the second lightguide 6 is inclined to the first 5.
  • variable optical attenuator shown in Figure 4 has curved channel walls 5,6.
  • the walls 5,6 curve away from each other as shown. Such curved walls again divert or reflect the beams away from the second lightguide 2 so reducing the Fabry Perot effect.
  • Shown in Figure 5 are the results of a numerical calculation of the insertion loss and return loss for a known parallel sided variable optical attenuator (as shown in Figure 1) and also a variable optical attenuator having a wedge shaped slot according to the invention (as shown in Figure 2) .
  • the calculations are performed using optical simulation software.
  • the calculations are performed by launching a modal field into the first lightguide 1 from the left.
  • the software returns the forward and backward propagating modes at the left and right waveguide respectively. From these power fractions one can calculate the return loss and insertion loss .
  • Shown in figure 6 is a further calculation using a slot width of lO ⁇ m, a waveguide width of lO ⁇ m, a slot angle of 7.2 degrees and a wedge angle of 0 degrees (parallel) and 5 degrees (wedge) . Again, the variation of wavelength dependent loss is significantly reduced.
  • the ripple in the insertion loss is caused by light reflected in the Fabry Perot cavity formed by the channel 4. It is believed that the amplitude of the ripple mainly depends on five factors - a) Channel width - the wider the channel 4 the further the reflected beam moves in one round trip in the channel 4 and so less is received by the second waveguide 2. However, the beam will diverge more so increasing insertion loss. b) Channel angle - increasing the angle of the channel 4 with respect to the lightguides 1,2 will cause the beam to traverse the channel 4 at a larger angle which again decreases the amount of light received by the second waveguide. However, both polarization dependent loss and insertion loss become worse.
  • Channel refractive index - by reducing the mismatch between the refractive index of the lightguides 1,2 and the channel 4 one can reduce the amount of reflection at the channel/waveguide interfaces.
  • the channel 4 is filled with a refractive index matching oil.
  • Waveguide width - increasing the width of the waveguides 1,2 has a similar effect to decreasing the index contrast. However, the vertical divergence does not change significantly.
  • FIG 9 Shown in Figure 9 is a further embodiment of a variable optical attenuator according to the invention.
  • the attenuator includes a shutter 7 which can be displaced within the slot by an actuator 8.
  • the shutter 7 enters the wide end of the slot 4.
  • the slot width narrows with increasing distance from the actuator 8.
  • the shutter enters the narrow end of the wedge shaped slot and the slot width increases with increasing distance from the actuator.
  • FIG. 10 Shown in Figure 10 is a further embodiment of a variable optical attenuator according to the invention.
  • the attenuator comprises a wedge shaped shutter 7 having a wedge angle of opposite sign to the slot angle.
  • the wedge angle is of the same sign but different magnitude to the slot angle.
  • the wedge angle is of the same sign and substantially the same magnitude as the slot angle.
  • the end walls of the lightguides 1,2 are coated with anti- reflection coating.
  • the wedge slot 4 is used in a switch device rather than a variable optical attenuator
  • the optical switch has open and closed configurations.
  • the switch transmits the light, substantially unattenuated, across the wedge slot 4, from a first lightguide 1 to a second lightguide 2.
  • the shutter which has a reflective coating in this embodiment, so as to act as a mirror
  • the wedge shaped slot 4 again gives the advantage of reduced wavelength dependent loss from the Fabry Perot effect, in the same manner as in the variable optical attenuator embodiment.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Light Control Or Optical Switches (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

A variable optical attenuator comprising a first lightguide (1) having a first end wall (5); a second lightguide (21) having a second end wall (6) arranged to directly receive light emitted from the first end wall; the first and second end walls defining a channel (4) for receiving a shutter (7); wherein at least a portion of the second end wall is inclined to the first end wall. Multiple reflections between the opposite walls of the channel (4) cause the channel (4) to act as Fabry Perot interferometer causing a substantial wavelength dependent loss in the attenuator. The non-parallel end faces (5, 6) increase the off-set of the reflected beam with respect to the first end face (5) (by comparision with parallel end faces). This suppresses the Fabry Perot effect.

Description

A VARIABLE OPTICAL ATTENUATOR
The present invention relates to variable optical attenuators and optical switches. More particularly, but not exclusively, the present invention relates to a variable optical attenuator having a channel for receiving a shutter, the channel being generally wedged shaped with one wall inclined to the other.
Known optical attenuators typically comprise first and second co-axial lightguides. The lightguides are separated by a channel substantially normal to the lightguides. A shutter is adapted to be displaced within the channels to attenuate light passing across the channel between the lightguides. The opposite sides of the channel are parallel and for reliability purposes the channel is filled with air. The higher refractive index difference between the lightguide and air results in considerable reflection at these sides of the channel. Due to repeated reflection of light from the opposite sides of the channel, the channel acts as a Fabry Perot resonator, causing considerable variation in wavelength dependent loss in the transmission response for the optical attenuator .
The present invention seeks to overcome the disadvantage of known optical attenuators.
According to a first aspect of the present invention there is provided a variable optical attenuator comprising: a first lightguide having a first end wall; a second lightguide having a second end wall arranged to directly receive light emitted from the first end wall ; the first and second end walls defining a channel for receiving a shutter; wherein at least a portion of the second end wall is inclined to the first end wall.
By inclining the second end wall with respect to the first end wall one reduces the ability of the channel to act as a Fabry Perot resonant cavity since reflected beams are generally reflected away from the lightguides. This in turn reduces the variation in wavelength dependent loss of the attenuator .
The variable optical attenuator can be an optical switch.
Preferably, the first and second lightguides are arranged in a substrate, the first and second end walls being perpendicular to the substrate.
The optical axis of the first and second lightguides can be co-axial. Alternatively, the optical axis of the first lightguide is parallel to but displaced from the optical axis of the second lightguide. As a further alternative the optical axis of the second lightguide is inclined to the optical axis of the first lightguide, reducing the insertion loss .
Preferably at least one of the first and second end walls is inclined to the optical axis of the respective lightguide proximate to the end wall, again reducing the insertion loss.
The channel can contain an index matching fluid, particularly an index matching oil.
At least a portion of one of the end walls can be curved, curving away from the opposite wall. According to another aspect of the invention there is provided an optical switch comprising: a first lightguide having a first end wall; a second lightguide having a second end wall arranged to directly receive light emitted from the first end wall; the first and second end walls defining a channel for receiving a mirror; a third lightguide having one end arranged to directly receive light reflected from the mirror; wherein at least a portion of the second end wall is inclined to the first end wall.
The present invention will now be described by way of example only, but not in any limitative sense with reference to the accompanying drawings in which
Figure 1 shows a known variable optical attenuator;
Figure 2 shows a variable optical attenuator according to the invention;
Figure 3 shows a further embodiment of a variable optical attenuator according to the invention;
Figure 4 shows a further embodiment of a variable optical attenuator according to the invention;
Figures 5 and 6 show the results of numerical calculations of the insertion loss and return loss for a known variable optical attenuator and an attenuator according to the invention;
Figure 7 shows measured insertion loss as a function of wavelength for a known parallel slot variable optical attenuator; Figure 8 shows measured insertion loss as a function of wavelength for a wedge slot variable optical attenuator according to the invention;
Figure 9 shows a variable optical attenuator according to the invention including a shutter;
Figure 10 shows a further embodiment of a variable optical attenuator according to the invention including a shutter; and
Figure 11 shows a switch according to a further embodiment of the invention.
Shown in Figure 1 is a known variable optical attenuator comprising first and second lightguides 1, 2 within a substrate 3. An air filled parallel channel 4 separates the first and second lightguides 1,2. A shutter (not shown) is adapted to be displaced within the channel 4 to attenuate the beam. Fig.l shows the "through-state" in which the shutter is not attenuating the beam.
In use a lightbeam is transmitted along the first lightguide 1. The beam exits the lightguide 1 at a first end wall 5 and is transmitted across the air filled channel 4 to the second end wall 6 of the second lightguide 2. At the second end wall 6 a portion of the light beam is transmitted into the second lightguide 2. However, due to the difference in refractive index between the air filled channel 4 and the lightguides 1,2 a portion of the beam is reflected as shown.
The reflected beam returns towards the first lightguide 1 where it is again partially reflected/transmitted. Multiple reflections between the opposite walls of the channel 4 cause the channel 4 to act as Fabry Perot interferometer causing a substantial wavelength dependent loss in the attenuator. As can be seen from Figure 1, the channel 4 can be inclined with respect to the normal to the lightguides 1,2. This causes the reflected beams to be displaced with respect to the beam. This reduces the number of reflected beams received by the lightguide 1, 2 as shown, so reducing the wavelength dependent loss. However, the wavelength dependent loss is still considered to be too high for many applications.
Shown in Figure 2 is a variable optical attenuator according to the invention. The attenuator comprises first and second lightguides 1,2 received within a substrate 3. First and second lightguide end walls 5,6 define an air filled channel 4 for receiving the shutter (not shown) . The first and second end walls 5,6 are inclined to their respective lightguides 1,2, so inclining the channel 4 to the lightguides 1,2 as can be seen. Unlike with known variable optical attenuators the end walls 5,6 are not parallel, the second end wall 6 is inclined to the first 5 to produce a wedge shaped channel 4. The inclination of the second end wall 6 to the first end wall 5 is the slot angle. The channel 4 extends into the substrate 3 as shown.
As can be seen, the non-parallel end faces 5,6 increase the off-set of the reflected beam with respect to the first end face 5 (by comparison with Figure 1) . This suppresses the Fabry Perot effect.
A further embodiment of a variable optical attenuator according to the invention is shown in Figure 3. In this embodiment the optical axis of the second lightguide 6 is inclined to the first 5.
The variable optical attenuator shown in Figure 4 has curved channel walls 5,6. The walls 5,6 curve away from each other as shown. Such curved walls again divert or reflect the beams away from the second lightguide 2 so reducing the Fabry Perot effect.
Shown in Figure 5 are the results of a numerical calculation of the insertion loss and return loss for a known parallel sided variable optical attenuator (as shown in Figure 1) and also a variable optical attenuator having a wedge shaped slot according to the invention (as shown in Figure 2) .
The calculations are performed using optical simulation software. The calculations are performed by launching a modal field into the first lightguide 1 from the left. The software returns the forward and backward propagating modes at the left and right waveguide respectively. From these power fractions one can calculate the return loss and insertion loss .
In Figure 5 the calculations were performed for a waveguide width of lOμm, a slot width of 15μm, a slot angle of 7.2 degrees and a wedge angle of 0 degrees (parallel) and 3 degrees (wedge) . The wedge angle is the inclination of the front shutter face to the back shutter face. As can be seen introducing a wedge angle significantly reduces the variation in wavelength dependent loss.
Shown in figure 6 is a further calculation using a slot width of lOμm, a waveguide width of lOμm, a slot angle of 7.2 degrees and a wedge angle of 0 degrees (parallel) and 5 degrees (wedge) . Again, the variation of wavelength dependent loss is significantly reduced.
Shown in Figure 7 are experimental measurements of insertion loss against wavelength for a known parallel slot device. The two lines show insertion loss for TE and TM polarisation states. The ripple caused by Fabry Perot effects can clearly be seen.
The ripple in the insertion loss is caused by light reflected in the Fabry Perot cavity formed by the channel 4. It is believed that the amplitude of the ripple mainly depends on five factors - a) Channel width - the wider the channel 4 the further the reflected beam moves in one round trip in the channel 4 and so less is received by the second waveguide 2. However, the beam will diverge more so increasing insertion loss. b) Channel angle - increasing the angle of the channel 4 with respect to the lightguides 1,2 will cause the beam to traverse the channel 4 at a larger angle which again decreases the amount of light received by the second waveguide. However, both polarization dependent loss and insertion loss become worse. c) Channel refractive index - by reducing the mismatch between the refractive index of the lightguides 1,2 and the channel 4 one can reduce the amount of reflection at the channel/waveguide interfaces. In an alternative embodiment of the invention the channel 4 is filled with a refractive index matching oil. d) Refractive index contrast of the lightguides - decreasing this would widen the modal field making the divergence angle smaller. This would reduce the insertion loss but increase ripple. e) Waveguide width - increasing the width of the waveguides 1,2 has a similar effect to decreasing the index contrast. However, the vertical divergence does not change significantly.
Shown in Figure 8 are experimental measurements of insertion loss against wavelength for a variable optical attenuator according to the invention. Again, loss for both TE and TM modes is shown. It can clearly be seen that the insertion loss ripple is reduced.
Shown in Figure 9 is a further embodiment of a variable optical attenuator according to the invention. The attenuator includes a shutter 7 which can be displaced within the slot by an actuator 8. In this embodiment the shutter 7 enters the wide end of the slot 4. The slot width narrows with increasing distance from the actuator 8.
In an alternative embodiment (not shown) the shutter enters the narrow end of the wedge shaped slot and the slot width increases with increasing distance from the actuator.
Shown in Figure 10 is a further embodiment of a variable optical attenuator according to the invention. The attenuator comprises a wedge shaped shutter 7 having a wedge angle of opposite sign to the slot angle. In an alternate embodiment (not shown) the wedge angle is of the same sign but different magnitude to the slot angle. In a further embodiment (not shown) the wedge angle is of the same sign and substantially the same magnitude as the slot angle.
In an alternative embodiment of the invention (not shown) the end walls of the lightguides 1,2 are coated with anti- reflection coating.
In a further embodiment of the invention, shown in Fig.11, the wedge slot 4 is used in a switch device rather than a variable optical attenuator The optical switch has open and closed configurations. In the open configuration, shown in Fig.11, the switch transmits the light, substantially unattenuated, across the wedge slot 4, from a first lightguide 1 to a second lightguide 2. In the closed configuration of the switch the shutter (which has a reflective coating in this embodiment, so as to act as a mirror) is moved into the space between the first and second lightguides 1,2 so as to substantially completely reflect the light from the first lightguide 1 into a third lightguide 9. In the open configuration the wedge shaped slot 4 again gives the advantage of reduced wavelength dependent loss from the Fabry Perot effect, in the same manner as in the variable optical attenuator embodiment.

Claims

1. A variable optical attenuator comprising : a first lightguide having a first end wall; a second lightguide having a second end wall arranged to directly receive light emitted from the first end wall; the first and second end walls defining a channel for receiving a shutter; wherein at least a portion of the second end wall is inclined to the first end wall.
2. A variable optical attenuator as claimed in claim 1, wherein the first and second lightguides are arranged on a substrate; the first and second end walls being perpendicular to the substrate.
3. A variable optical attenuator as claimed in either of claims 1 or 2, wherein the optical axis of the first and second lightguides are co-axial.
4. A variable optical attenuator as claimed in either of claims 1 or 2, wherein the optical axis of the first lightguide is parallel to and displaced from the optical axis of the second lightguide.
5. A variable optical attenuator as claimed in either of claims 1 or 2, wherein the optical axis of the second lightguide is inclined to the optical axis of the first lightguide .
6. A variable optical attenuator as claimed in any one of claims 1 to 5, wherein the normal axis to at least one of the first and second end walls is inclined to the optical axis of its respective lightguide proximate to the end wall.
7. A variable optical attenuator as claimed in any one of claims 1 to 6, wherein the channel contains an index matching fluid.
8. A variable optical attenuator as claimed in any one of claims 1 to 7, wherein at least one portion of one of the end walls is curved, curving away from the opposite wall .
9. An optical switch comprising: a first lightguide having a first end wall; a second lightguide having a second end wall arranged to directly receive light emitted from the first end wall; the first and second end walls defining a channel for receiving a mirror; a third lightguide having one end arranged to directly receive light reflected from the mirror; wherein at least a portion of the second end wall is inclined to the first end wall.
PCT/GB2003/003611 2002-08-23 2003-08-19 A variable optical attenuator WO2004019087A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0219794.5 2002-08-23
GB0219794A GB0219794D0 (en) 2002-08-23 2002-08-23 A variable optical attenuator

Publications (2)

Publication Number Publication Date
WO2004019087A2 true WO2004019087A2 (en) 2004-03-04
WO2004019087A3 WO2004019087A3 (en) 2006-05-11

Family

ID=9942948

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2003/003611 WO2004019087A2 (en) 2002-08-23 2003-08-19 A variable optical attenuator

Country Status (2)

Country Link
GB (1) GB0219794D0 (en)
WO (1) WO2004019087A2 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105372798A (en) * 2015-12-08 2016-03-02 中国科学院上海光学精密机械研究所 High-energy reflection type optical attenuator
CN110986819A (en) * 2019-12-16 2020-04-10 西安工业大学 Fabry-Perot cavity type optical fiber curvature sensing probe and manufacturing method thereof

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5917985A (en) * 1995-12-30 1999-06-29 Korea Electronic Technology Institute Optical attenuator
US6301425B1 (en) * 1999-02-22 2001-10-09 Agere Systems Optoelectronics Guardian Corp. Magnetically tunable optical attenuator and method of attenuating signals
WO2003042733A1 (en) * 2001-11-09 2003-05-22 Active Optical Networks, Inc. Micro-electro-mechanical variable optical attenuator

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5685702A (en) * 1979-12-14 1981-07-13 Fujitsu Ltd Variable attenuator
JPS56102825A (en) * 1980-01-19 1981-08-17 Ritsuo Hasumi Thick film variable light attenuator
JPS5933404A (en) * 1982-08-18 1984-02-23 Nippon Telegr & Teleph Corp <Ntt> Optical attenuator
JPS6465506A (en) * 1987-09-04 1989-03-10 Seiko Instr & Electronics Optical attenuator
JPH06294911A (en) * 1993-04-08 1994-10-21 Toray Ind Inc Optical fixed attenuator and its manufacture
JP2847619B2 (en) * 1994-09-26 1999-01-20 ヒロセ電機株式会社 Variable optical attenuator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5917985A (en) * 1995-12-30 1999-06-29 Korea Electronic Technology Institute Optical attenuator
US6301425B1 (en) * 1999-02-22 2001-10-09 Agere Systems Optoelectronics Guardian Corp. Magnetically tunable optical attenuator and method of attenuating signals
WO2003042733A1 (en) * 2001-11-09 2003-05-22 Active Optical Networks, Inc. Micro-electro-mechanical variable optical attenuator

Non-Patent Citations (6)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 005, no. 154 (P-082), 29 September 1981 (1981-09-29) & JP 56 085702 A (FUJITSU LTD), 13 July 1981 (1981-07-13) *
PATENT ABSTRACTS OF JAPAN vol. 005, no. 173 (P-087), 5 November 1981 (1981-11-05) & JP 56 102825 A (HASUMI RITSUO), 17 August 1981 (1981-08-17) *
PATENT ABSTRACTS OF JAPAN vol. 008, no. 129 (P-280), 15 June 1984 (1984-06-15) & JP 59 033404 A (NIPPON DENSHIN DENWA KOSHA), 23 February 1984 (1984-02-23) *
PATENT ABSTRACTS OF JAPAN vol. 013, no. 276 (P-890), 26 June 1989 (1989-06-26) & JP 01 065506 A (SEIKO INSTR & ELECTRONICS LTD), 10 March 1989 (1989-03-10) *
PATENT ABSTRACTS OF JAPAN vol. 1995, no. 01, 28 February 1995 (1995-02-28) & JP 06 294911 A (TORAY IND INC), 21 October 1994 (1994-10-21) *
PATENT ABSTRACTS OF JAPAN vol. 1996, no. 08, 30 August 1996 (1996-08-30) & JP 08 094843 A (HIROSE ELECTRIC CO LTD; JAPAN RADIO CO LTD), 12 April 1996 (1996-04-12) *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105372798A (en) * 2015-12-08 2016-03-02 中国科学院上海光学精密机械研究所 High-energy reflection type optical attenuator
CN110986819A (en) * 2019-12-16 2020-04-10 西安工业大学 Fabry-Perot cavity type optical fiber curvature sensing probe and manufacturing method thereof
CN110986819B (en) * 2019-12-16 2021-04-06 西安工业大学 Fabry-Perot cavity type optical fiber curvature sensing probe and manufacturing method thereof

Also Published As

Publication number Publication date
GB0219794D0 (en) 2002-10-02
WO2004019087A3 (en) 2006-05-11

Similar Documents

Publication Publication Date Title
US5475772A (en) Spatial filter for improving polarization extinction ratio in a proton exchange wave guide device
US6243516B1 (en) Merging optical waveguides having branch angle within a specific range
US5539577A (en) Means to lessen unwanted reflections in an optical device
US7366372B2 (en) Waveguide device having improved spatial filter configurations
US6718114B2 (en) Variable optical attenuator of optical path conversion
JPH09505673A (en) Waveguide coupler
EP2691801A1 (en) Optical device having an elastomeric waveguide switch body and related methods
US6775459B2 (en) Variable optical attenuator
KR100483048B1 (en) Mems variable optical attenuator
US6882764B1 (en) Polarization independent packaging for polarization sensitive optical waveguide amplifier
WO2004019087A2 (en) A variable optical attenuator
US7574096B2 (en) Optical attenuator
US7697801B2 (en) Wavelength selective switch
CN108333681B (en) On-chip integrated partial reflector based on partial transmission type angular reflector group
US7062120B2 (en) Optical device and movable reflector
US7408713B1 (en) Step-phase interferometric optical interleaver
KR100361441B1 (en) tap coupler
EP1531350B1 (en) Optical device for varying the power of light having a movable reflector
JP3036613B2 (en) Matrix optical waveguide switch
US20220357517A1 (en) Wavelength division multiplexing structure
EP4283354A1 (en) An optical structure
KR100690073B1 (en) Variable optical attenuator
JP2004163175A (en) Light lateral monitoring system
Liu et al. Improved efficiency narrow-band acoustooptic tunable reflector using fibre Bragg grating
JPH01285913A (en) Optical parts

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A2

Designated state(s): CN JP US

AL Designated countries for regional patents

Kind code of ref document: A2

Designated state(s): AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LU MC NL PT RO SE SI SK TR

121 Ep: the epo has been informed by wipo that ep was designated in this application
122 Ep: pct application non-entry in european phase
NENP Non-entry into the national phase in:

Ref country code: JP

WWW Wipo information: withdrawn in national office

Country of ref document: JP