KR20030034050A - Compression-tuned grating-based optical add/drop multiplexer - Google Patents

Abstract

The reconfigurable wavelength add / drop module based on the compression tuned fiber Bragg grating has a compression force assembly, and all glass Bragg grating compression units have a spaced grating along the axis of compression. The compression force assembly is responsive to a control electronic signal containing information about the selected wavelength of the channel added to or dropped from the optical traffic signal to provide a compression force applied along the axis of compression. The compression unit is responsive to the optical traffic signal and the compressive force to provide all glass Bragg grating compression unit optical signals having a selected wavelength of the channel added to or dropped from the optical traffic signal. The compression unit optical signal may include either traffic with added reflection channels or dropped reflection channels. The compression unit is a "dogbone" structure with either a glass tube with optical fibers fused therein or a single large diameter waveguide with a core. The core of an optical fiber or waveguide has a spaced grating therein. The axis of compression is parallel to the longitudinal axis of the canine structure.

Description

Optical Add / Drop Multiplexer Based on Compression Tuning Gratings {COMPRESSION-TUNED GRATING-BASED OPTICAL ADD / DROP MULTIPLEXER}

The telecommunications sector is changing dramatically with increasing competition, intense bandwidth demands, and the shift towards more data-centric network structures. First-generation point-to-point waveform-separated multiplex systems are easily bottlenecked in the backbone of the network. As new cross-connect architectures move technology closer to the subscribers of the network, operators are challenging to provide services at the optical layer, which is a desire for more flexible networks that can switch and transmit wavelengths. This is of great importance and demand for wavelength attenuation devices in which the compression tuning grating device plays a major role.

The need to provide wavelength "just in time" services by the allocation of wavelengths and more movement of the optical layer from the high-capacity backbone to the local loop is directed towards all optical networks where the basic network requirements are fulfilled at the optical layer. Transform

Optical networks are a natural evolution of point-to-point dense wavelength division multilpexing (DWDM) that delivers a more dynamic, flexible and intelligent networking architecture to improve service delivery time. The main element of an optical network is the wavelength, which is supplied, organized, delivered, and managed in the optical domain. Intelligent optical networking is first deployed as an "opaque" network where periodic optical-electrical conversion is required for monitor and split signal damage. Longer-range optical networks develop into "transparent" optical networks in which the signal is entirely transmitted from its source to its destination in the optical domain.

A key element of modern optical networks is the optical add / drop multiplexer (OADM). OADM will add and drop certain wavelength channels without affecting them through the channel. Fixed OADM simplifies the network and easily allows cost-impact DWDM migration from a simple point-point configuration to a fixed multi-point configuration. True dynamic OADM with reconstruction in the optical domain without photoelectric conversion allows for a dynamically reconfigurable multi-point DWDM optical network. This dynamically reconfigurable multi-point architecture is expected to be the next major phase in network deployment in accordance with the true OADM that enables the network for this architecture.

Commercially known is a fixed full optical OADM, which combines a fixed optical channel filter, typically an optical fiber Bragg grating, with passive optical paths and branching components such as couplers and circulators. The fiber Bragg grating is not adjusted to filter other wavelengths.

The adjustable grating / circulator approach for the dynamically reconfigurable OADM is also in accordance with the prior art by columns or deformations to adjust the grating. This dynamic or programmable all-optical OADM design is based on an adjustable grating. However, thermal regulation is slow and difficult to maintain and control the wavelengths with the tolerances required by current DWDM systems whose appearance is sub-nanometer channel space. The strain adjustment approach in which the fiber grating is mechanically stretched has also proved difficult to maintain, control, and adjust the wavelength due to fiber attachment challenges and minor mechanical strains that cause errors and deviations. The reliability of optical fibers maintained under stress over extended periods of time is problematic and controversial for use in industry.

In US Pat. No. 6,020,986, incorporated herein by reference, Ball discloses an add / drop module with a circulator 16, an array of adjustable fiber Bragg gratings, a piezoelectric device, and a controller. Strain is applied by coupling the piezoelectric device to each optical fiber Bragg grating to adjust the current applied from the controller to each piezoelectric device. The wavelength of the grating can be adjusted within the nanometer range for gratings having a wavelength of about 1540 nanometers. However, the balls do not disclose how the piezoelectric device is physically coupled to the optical fiber Bragg grating to apply strain. See also US Pat. No. 5,579,143, issued to Huber, which is incorporated herein by reference, and US Pat. No. 5,748,349, assigned to Mizrahi, which discloses an OADM system with adjustable filters.

Moreover, a grating / circulator approach for OADM has proven to be a viable way to overcome other OADM technologies such as naturally wideband optical switches and arrayed waveguide devices. The combination of switch and wavelength multiplexer achieves wavelength selection, but suffers from other performance issues such as high light loss and high cost.

Despite intense effort, this type of dynamic OADM remains difficult due to inherent performance issues, particularly drift and reliability, rather than a thermal or stress grating adjustment approach. Inadequate thermal and stress-based grating adjustment methods to control and maintain wavelengths with tight tolerances can be achieved by providing a feedback and reference for closed loop control of grating wavelengths, such as wavelength monitoring devices or spectrum analyzers. Requires some alignment of line signal characteristics.

TECHNICAL FIELD The present invention relates to an optical add / drop multiplexer, and more particularly, to an optical add / drop multiplexer (OADM) using a large-diameter waveguide for dynamically adding and dropping an optical signal from a WDM optical signal.

1 is a side view and a block diagram of a position / force feedback control circuit of an adjustable grating unit of an adjustable optical filter according to the present invention;

2 is a side view of the grating element of the adjustable optical filter according to the invention,

3 is a block diagram of an adjustable drop filter in accordance with the present invention;

4 is a block diagram of another embodiment of an adjustable drop filter in accordance with the present invention;

5 is a block diagram of an adjustable add filter in accordance with the present invention;

6 is a block diagram of another embodiment of an adjustable add filter in accordance with the present invention;

7 is a block diagram of another embodiment of an adjustable add filter in accordance with the present invention;

8 is a block diagram of another embodiment of an adjustable add filter in accordance with the present invention;

9 is a block diagram of a reconfigurable optical add / drop multiplexer (ROADM) in accordance with the present invention;

10 is a block diagram of another embodiment of a reconfigurable optical add / drop multiplexer (ROADM) in accordance with the present invention;

11 is a block diagram of another embodiment of a reconfigurable optical add / drop multiplexer (ROADM) in accordance with the present invention;

12 is a block diagram of another embodiment of a reconfigurable optical add / drop multiplexer (ROADM) in accordance with the present invention;

13 is a block diagram of another embodiment of a reconfigurable optical add / drop multiplexer (ROADM) in accordance with the present invention.

According to an embodiment of the invention, the optical drop filter comprises a compression tuning optics. Compression tuning optics include an optical waveguide having an inner core disposed within the outer cladding and a grating disposed within the inner core. The grating reflects the first reflected wavelength of light backwards along the inner core and propagates the remaining wavelengths of light through it. An optical waveguide has a pair of opposing surfaces. The optical waveguide also includes a compression device for compressing the opposing surfaces towards each other to tune the grating to change the reflected wavelength of the light reflected backwards along the inner core. The drop filter also includes an optical directing device for providing an input optical signal to the compression tuning optics. The input optical signal has a plurality of optical channels centered on wavelengths at constant intervals. The compression tuning optics removes the optical channel from the input optical signal.

According to another embodiment of the present invention, the optical adding filter includes a compression tuning optics having an optical waveguide. The optical waveguide includes an inner core disposed within the outer cladding and a grating disposed within the inner core. The grating reflects the first reflected wavelength of light backwards along the inner core and propagates the remaining wavelengths of light through it. An optical waveguide has a pair of opposing surfaces. Compressors compress the opposing surfaces towards each other to tune the grating to vary the reflected wavelength of reflected light back along the inner core. An optical directing device combines an added optical channel with an input optical signal having a plurality of optical channels centered at wavelengths which are optically connected to the compression tuning optics to maintain a constant spacing. The input optical signal has a plurality of optical channels centered on wavelengths at constant intervals. The compression tuning optics provide an optical channel coupled with the input optical signal to provide a combined output signal.

According to another embodiment of the present invention, the optical addition / drop filter comprises a compression tuning optics having an optical waveguide. The optical waveguide includes an inner core disposed within the outer cladding and a grating disposed within the inner core. The grating reflects the first reflected wavelength of light backwards along the inner core and propagates the remaining wavelengths of light through it. An optical waveguide has a pair of opposing surfaces. Compressors compress the opposing surfaces towards each other to tune the grating to vary the reflected wavelength of reflected light back along the inner core. An optical directing device combines the added optical channel with an input optical signal having a plurality of optical channels centered at wavelengths which are optically connected to the compression tuning optics and which maintain a constant interval. The input optical signal has a plurality of optical channels centered on wavelengths at constant intervals. The compression tuning optics provide an optical channel coupled with the input optical signal to provide a combined output signal.

According to another embodiment of the present invention, the compression tuning optical addition / drop module includes a compression device for providing a compression force applied along the axis of compression. The grating compression unit has a grating along the axis of compression in response to the optical input signal, and provides a grating compression unit optical signal having a selected wavelength of the channel added to or dropped from the input signal to the optical input signal and the compression force. Answer.

3 shows each embodiment of a tunable drop filter 80, 90 that filters or drops an optical channel or at least one wavelength band of light centered at each channel wavelength from the WDM optical input signal 11. 5 through 8 illustrate each embodiment of a tunable add filter 100, 110, 120, 130 that adds or combines at least one channel to the WDM optical input signal 11. 9 to 13, tunable drop and add filters 80, 90, 100, 110, 120, 130 provide replaceable optical add / drop multiplexer (ROADM) 140, 150, 160, 170, 180 To be combined in a number of ways.

1 and 2, each of the tunable drop filters, add filters, and ROADMs shown in FIGS. 3 to 13 may include a single port optical indicator 12, such as a three or four port circulator or optical coupler 15, 13; at least one tunable Bragg grating unit 10 optically coupled to the FIG. The grating unit 10 tunes a grating element 14 which is a bulk or large diameter optical waveguide having an outer cladding 18 and an inner core 16 arranged inside of a single mode. The grating element 14 is made of silica glass (SiO ₂ ) having an outer diameter of at least 0.3 mm and having a suitable dopant so that light 11 can propagate along the inner core 16 as known. The grating element (large diameter optical waveguide) is designed to measure the dimensions and internal dimensions of the desired core described above, similar to those described in pending US patent application Ser. No. 09 / 455,868, entitled "Large diameter optical waveguide, grating, and laser." Provided is formed by using fiber drawing technology, now known and later developed. The grating element is then etched, ground or machined to form a "dogbone" shape, as described in detail below. A pair of fibers or “pigtails” 17 is attached to the ends of the grating element 14 by known techniques such as epoxy or glass melting.

Further, the optical grating element 14 may be formed by a laser, filament, flame, or the like, as described in pending US patent application Ser. No. 09 / 455,865, entitled "Tube-Encased Fiber Grating" incorporated herein by reference. It is formed by heating, collapsing and dissolving glass capillary tubes in a fiber (not shown). US Pat. No. 5,745,626, entitled "Method for and Encapsulation of anoptical fiber" by Duck et al., Incorporated herein by reference for the purpose of understanding the invention, and "Method of making fiber coupler having integral precision connection wells" by Berkey. As described in US Pat. No. 4,915,467, or other techniques, designated ", another technique is used to disintegrate and dissolve tubes in fibers. In addition, to fuse the fibers to the tube using a high temperature glass solder such as silica solder (powder or solid), or by laser welding / melting or another dissolution technique, such that the fibers, tubes and solder are all fused together. Other techniques are used.

The grating element 14 includes a reflective element 20, such as a Bragg grating, and is written in (embedded or taken) into the inner core 16 of the grating element 14. The Bragg grating 20 reflects back a portion of the input light 11 as indicated by line 22 having a predetermined wavelength band of light centered on the reflected wavelength λ _b , and the remaining wavelength of incident light as indicated by line 24. Pass As is known, the grating 20 is described in US Pat. Nos. 4,725,110 and 4,807,950, designated "Method for impressing gratings within fiber optics" by Glenn et al. , As described in U.S. Patent 5,388,173, entitled "Method and apparatus for forming aperiodic gratings in optical fibers" by Glenn.

However, if desired, a wavelength-tunable grating or reflecting element 20 is used that fits into the inner core 16, writes, etches, stamps or otherwise forms. As used herein, the term "lattice" means such a reflective element. Moreover, reflective element (or grating) 20 is used for reflection and / or transmission of light.

If desired, other materials and dimensions of the optical grating element 14 are used. For example, the grating element 14 is made of glass, such as silica, phosphate glass, or other glass, or made of glass and plastic or plastic alone.

The grating element 14 is excavated by a compression device or housing 30 similar to that described in US patent application Ser. No. 09 / 707,084 entitled "Compression-tuned bragg grating based laser" (CiDRA Docket No.CC-0129D). Compressed mostly. One end of the grating element 14 is pressed against the seat 32 of the one end 34 of the housing. The housing also has a pair of arms (or sides) 36 that guide the movable block. Block 38 has a sheet 40 that presses against the other end of the grid element 14. The axial cross-section and / or mating faces 32 and 40 of the grating element 14 are plated with a material that enhances or reduces the stress of mating the grating element 14 with a sheet on a pair of surfaces. The ends of the housing 30 and the block 38 have holes 42 drilled to penetrate the fibers. The ends 34 of the housing 30 and the block 38 provide a plane instead of the concave sheets 32, 40 to have each end of the coplanar grating element 14.

The housing 30 is assembled such that pre-strain or pre-stain is present in the grating element 14 before applying an external force.

Actuator 44, such as a piezoelectric (PZT) actuator, functions as a moveable block 38 that causes the block to move as indicated by arrow 46. The PZT actuator 44 thus tunes the grating 20 to the desired reflected wavelength by providing a predetermined force on the moving block 38 to compress the grating element 14. By controlling the signal generated by the displacement control circuit or controller 50 via the conductor 52, the PZT actuator 44 generates the appropriate pressure necessary to tune the grating element to the desired Breg reflected wavelength of the grating 20. Is activated to provide. Control circuit 50 expands actuator 44 in response to input command 54 and displacement sensor 56 providing feedback indicative of strain or compression of grating element 14 to form a non-optical closed loop control configuration. And contraction. That is, light 11 propagating through the network or device is not used to provide feedback for tuning the grating 20.

In one embodiment, a pair of capacitive elements similar to those described in pending US patent application Ser. No. 09 / 519,802, entitled “Tunable optical structure featuring feedback control,” filed March 6, 2000, fully incorporated by reference. Reference numeral 58 and a replacement sensor circuit 59; As shown in FIG. 1, each capacitive element 58 is generally a tube having an annular capacitive end surface 60. The capacitive element 58 is installed at each end of the grating element 14 such that the capacitive surface 60 is spaced a predetermined distance, such as about 1-2 microns. If desired, another interval is used. The capacitive element 58 is bonded or fixed using an epoxy or other tacky compound, or fused to the grating element 14 using a CO ₂ laser or other heating element. Capacitive surface 60 is coated by a metal coating such as gold to form a pair of annular capacitive plates 64. The change in capacity is due to the change in the space between the capacity plates.

The electrode 66 is attached to the capacitor plate 64 to connect the capacitor to the displacement sensor circuit 59. The displacement sensor circuit 59 measures the capacitance between the capacitor plates 64 and provides the displacement controller 50 with a detection signal 67 representing the measured capacitance. As the grating element 14 is strained, the gap between the capacitive plates 64 in parallel changes, so that the capacitance can be changed correspondingly. In particular, as the grating is compressed, the gap between the capacitive plates 64 is reduced, resulting in an increase in capacity. The change in capacitance is inversely proportional to the change in reflected wavelength λ _b of grating 20. Since the capacitive element 58 is directly connected to the grating element 14, the capacitive element is passive and does not slip. The sensor electronics 59 can be implemented without undue experimentation to measure the change in capacitance between two capacitive plates 64.

In operation of the grating element 10, the controller 50 receives a wavelength input signal 54 representing the desired reflected wavelength to tune the grating element. According to the input signal 54 and the detection signal 67 representing the current reflected wavelength of the grating 20, the controller 50 applies the pressure applied to the grating element 14 to set the desired reflected wavelength of the grating 20. The control signal 52 is provided to the actuator 44 to increase or decrease. The change in force applied to the grating element 14 changes the spacing between the ends of the grating 20 and thus the spacing between the capacitive plates 64. As described above, the change in the spacing of the capacitive plates 64 changes the capacitance therebetween provided to the sensor circuit 59 for providing substitution feedback to the controller 50. Although the sensor circuit 59 and the controller 50 are shown as two separate elements, it can be seen that the functions of these elements are combined into a single element. Examples of closed loop actuators 44 used are model number CM (controller) and DPT-C-M (of cylindrical actuator) manufactured by Queensgate, Inc. of New York.

Although the present invention has been described using capacitor 56 to measure the gap distance, other gap sensing techniques such as inductive, optical, magnetic, microwave, and time based gap sensors can be used. Moreover, the background of the present invention is to include measuring or sensing the force applied to the compression element, and supplying it in reverse to control compression tuning of the optical structure. Although the embodiment of the present invention described above includes means for providing feedback of substitution of the grating element 20, it can be seen that the grating unit is accurate and repeatable and therefore operates in open loop mode.

Further, instead of using the piezoelectric actuator 44, the grating element 14 is replaced by another actuator, such as a solenoid, a pneumatic actuator, or another device capable of directly or indirectly applying axial pressure to the grating element 14. Is compressed. Moreover, stepper motors or another type of motor whose rotation or position can be controlled are used to compress the grating element. Mechanical interlocks are described in pending US patent application Ser. No. 09 / 751,589 (CC-0274A), entitled "Wide range tunable optical filter," filed Dec. 29, 2000, incorporated herein by reference; Movement to cause the block to move as indicated by arrow 46 similar to that described in US Patent Application Serial No. 09 / 752,332 (CC-0322), filed December 29, entitled "Actuator mechanism for tuning an optical device." A motor, such as a screw drive, a linear actuator, a gear, and / or a cam, is connected to the enable block 38 (or piston). The stepper motor is driven in a microstepping mode as described in US Pat. No. 5,469,520, referred to above as "Compression tuned fiber grating" by Morey et al. (Eg, Melles Griot NANOMOVER) incorporated herein by reference. It is a high resolution stepper motor.

As shown in FIG. 2, the grating element 14 may have a “dogbone” shape with a narrow central section 70 and a larger outer section 72. The dog bone shape provides increased sensitivity to the conversion force applied by the actuator 44, ensuring accurate tuning of the grating 20. The narrow section 70 may have an outer diameter d2 of 0.8-1 mm and a length L2 of approximately 5-20 mm. Each of the large sections 72 has a diameter d3 of approximately 2-3 mm and a length L3 of approximately 2-5 mm. The total length L1 is approximately 10-30 mm and the multi-component grating has a length Lg of approximately 5-20 mm. Other lengths and diameters of sections 70 and 72 can be used. Other dimensions and lengths for the grating element 14 and the multi-component gratings can be used.

The inner transition region 74 of the large section 72 can be a sharp vertical or angled edge or can be curved. The curved geometry has less stress risers than the sharp edges and can therefore reduce likely breakage. Also, the large section 72 may have an outwardly fluted section 76 at its end.

This dimensional change between the diameter d3 of the large section 72 and the diameter d2 of the narrow section 70 provides increased force to the grating wavelength shift sensitivity (or gain or scale factor) by strain amplification. In addition, the dimensions provided for dog bone in this specification may be scalable to provide a favorable amount of sensitivity.

Dimensions and geometries for certain embodiments described herein are for illustrative purposes only, and may be determined depending on the application and size, performance, fabrication, requirements, or other factors, taking into account the teachings herein. Any other dimension may be used if desired.

The grating element 14 is provided with a sheet for the grating element 14 for mating with the housing 30 and the moving block 38 and / or for adjusting the force angle on the grating element or for other reasons. It has an outer corner or edge 76 tapered (or beveled or angled) to provide. The angle of the beveled corner 76 is set to achieve the desired function. Additionally, one or both of the ends of the axis of the grating element 14 to which the fibers 41 are attached may have sections 78 of the outer tapered (or fluted, conical, or nipple) axis.

As disclosed in pending US Patent Application No. 09 / 455,865 (CiDRA Docket No.CC-0078B), filed December 6, 1999, filed "Tube-Encased Fiber Grating," incorporated herein by reference. For the grating element 14 formed by collapsing the tube into the fiber, after the capillary tube is wrapped or fused around the fiber, the Bragg grating can be written to the fiber. After the tube is wrapped around the lattice, the lattice 20 is lit in the fiber, US-named "Method and Apparatus For Forming A Tube-Encased Bragg Grating," filed Dec. 4, 1998, incorporated herein by reference. By certain preferred techniques such as patent application No. 09 / 205,845 (CiDRA Docket No. CC-0130) the grating is lit through a tube into the fiber.

The tunable grating unit 10 is actively modulated to provide a reconfigurable optical add / drop multiplexer (ROADM), while the present invention provides a tunable grating unit, a fixed optical add / drop multiplexer (FOADM). It is contemplated that a thermal grating unit that passively tunes the grating element 14 to maintain the reflected wavelength of the grating 20 over a set temperature range to provide. The thermal grating unit is similar to that disclosed in US patent application Ser. No. 09 / 699,940 (CC-0234A), filed "Temperature Compensated Optical Device," filed October 30, 2000, incorporated herein by reference. It is also contemplated that some or all of the grating units may replace the thermal grating units.

Referring to FIG. 3, the tunable drop filter 80 includes a plurality of tunable Bragg grating units 10 optically coupled in series to the ports of an optical directing device 12, such as a three port circulator. At least one grating unit 10 is actuated to urge each grating element 14 and thus to tune each grating 20 to reflect the desired optical channel dropped from the optical input signal 11, while the other grating Unit 10 is tuned or parked through the remaining channels of input signal 11.

In operation of the drop filter 80, the first port 81 of the circulator 12 is the wavelength transmitted through the optical fiber 82 Receives an input signal 11 having an optical channel centered at. The input signal 11 can be started from a light source or tapped off an optical network (not shown). The circulator 12 guides the input signal 11 clockwise to the second port 83 of the circulator. The input signal 11 exits to the second port 83 and proceeds through the optical fiber 85 to the grating element 14 of the grating unit 10.

An optional number of grating elements 10 is tuned to reflect the corresponding optical channel of the input signal 11, effectively dropping the corresponding optical channel from the input signal 11. The remaining optical grating unit 10 is tuned or parked to pass the remaining optical channel of the input signal 11 to provide an optical signal 86 that does not include the dropped optical channel. For example, as shown in FIG. 3, the pair of grating units 10 has a wavelength. While reflecting an optical signal having an optical channel centered on the remaining grating unit 10 Parked or tuned to pass the remaining channels centered on. The grating unit 10 is another grating unit in which the filter function of the grating 20 is parked between the optical channels, parked outside the range of the optical channel of the input signal 11, or tuned to reflect the optical signal. It can be parked by tuning the grating unit to park at the same wavelength as the grating.

The reflected optical channel propagates back to the second port 83 of the circulator 12 and then guides the reflected channel to the third port 87 of the circulator and provides the optical drop 89 to provide a drop optical signal 89. Guided through filter 88.

4 shows a tunable drop filter 90 of another embodiment. Tunable drop filter 90 includes a plurality of tunable Bragg grating units 10 that are selectively coupled in series to a port of an optical directing device 12, such as a three-port circulator. At least one grating unit 10 is activated to compress each grating element 14 and therefore tunes each grating 14 to pass a desired optical channel dropping from the optical input signal 11, while the other The grating unit is tuned to reflect the remaining optical channels of the input signal.

In operation of the drop filter 90, the first port 91 of the circulator 12 is the wavelength transmitted through the optical fiber 92. Receives an input signal 11 having an optical channel centered at. The input signal 11 can start from a light source and tap off the optical network (not shown). The circulator 12 guides the input signal 11 to the second port 93 of the circulator in a counterclockwise direction. The input signal 11 exits the second port 93 and propagates through the optical fiber 94 to the grating element 14 of the grating unit 10.

Each of the grating elements 14 is tuned or parked to pass a corresponding optical channel of the input signal 11 and effectively drops the corresponding optical channel from the input signal. The selected number of optical grating units are tuned to reflect the remaining optical channels of the input signal 11, providing an optical signal 98 that does not include the dropped optical channels. For example, as shown in FIG. Each of the units 10 has a wavelength While each is tuned or parked to pass an optical signal 95 having an optical channel centered at Tuned to reflect the remaining channel centered on.

The reflected optical channel centered at is propagated back to the second port 93 of the circulator 12, and then guides the reflected channel to the third port 96 of the circulator, and output optical signal 98. Guiding through the optical filter 97 to provide.

Referring to FIG. 5, the tunable addition filter 100 includes a plurality of tunable Bragg grating units 10 selectively coupled in series to a port of an optical directing device 13, such as a three-port circulator. . At least one grating unit 10 is movable to compress each grating element 14 and thus passes through each grating 20 to reflect the desired optical channel added to the optical input signal 11, while the other The grating unit is tuned to pass an optical channel of the input signal.

In the operation of the addition filter 100, the first port 101 of the circulator 13 receives the optical signal 102 added to the input signal 11. The added signal 102 is, for example, a precursor wavelength via the optical fiber 103. It has a single optical channel centered on it. The circulator 13 guides the added optical signal 102 clockwise to the second port 104 of the circulator. The added optical signal 102 exits the second port 104 and propagates through the optical fiber 105 to the grating element 14 of the grating unit 10. At least one grating element 14 is tuned to reflect the added signal 102 combined with the input signal 11. wavelength Input light 11 having an optical channel centered at is transmitted through the optical fiber 106 to the grating element 14 of the grating unit 10. The grating element 14 is tuned or parked to pass through the optical channel of the input signal 11 and has a wavelength Is combined with an added optical signal 102 to provide an optical signal 109 having an optical channel centered at.

The combined optical light propagates back to the second port 104 of the circulator 13, and then guides the optical light conditioned to the third port 107 of the circulator 13, and the wavelength Guided through the optical fiber 108 to provide an output signal 109 having an optical channel centered at.

While the addition filter 100 of FIG. 5 adds a single channel to the input light 11, those skilled in the art will appreciate that one or more optical signals that can add and provide the addition filter have a corresponding number of grating units 10 or additions. It is considered to have sufficient bandwidth to reflect adjacent optical channels.

6 illustrates an embodiment of a tunable add filter 110. Tunable add filter 110 includes a plurality of tunable Bragg grating units 10 that are selectively coupled in series to a port of an optional directing device 13, such as a three-port circulator. The grating unit 10 is activated to compress each grating element 14 and therefore tunes or parks the grating 20 to pass through the desired optical channel added to the optical input signal 11, while the other grating The unit 10 reflects or combines the channels of the input signal 11.

In the operation of the addition filter, the first port 111 of the circulator 13 has a wavelength transmitted through the optical filter 112. Receives an input signal 11 having an optical channel centered at. The input signal 11 can start from a light source and can tap off an optical network (not shown). The circulator 13 guides the input signal 11 counterclockwise to the second port 113 of the circulator. The input signal 11 comes out of the second port 113 and propagates through the optical fiber 114 to the grating element 14 of the grating unit 10. The selected number of grating elements 14 is the wavelength of the grating 20 in combination with the optically added signal 115. Tuned to reflect the optical chamber of the incident signal 11 centered at. wavelength An added signal 115 having an optical channel centered at is transmitted through the optical fiber 116 to the grating element 14 of the grating unit 10. Each grating unit 10 is tuned or parked to pass an optical channel of the added signal 115, and then the wavelength Is combined with the optical input signal 11 to provide a combined optical signal having an optical channel centered at.

The combined optical signal propagates back to the second port 113 of the circulator 13, and then guides the optical light coupled to the third port 117 of the circulator 13, and the wavelength Is combined with the optical input signal 11 to provide a combined optical signal having an optical channel centered at.

Referring to Fig. 7, since the tunable add filter 120 is the same as the tunable add filter of Fig. 5, the same components are denoted by the same reference numerals. The tunable addition filter 120 includes a plurality of tunable Bragg grating units 10 optically connected in series to the ports of the optical directing device 13, such as a three port circulator. Since at least one grating unit 10 is operated to compress each grating element 14, the grating 20 is tuned to reflect the desired optical channel to be added to the light input signal 11. The other grating unit 10 is tuned or parked to pass the remaining optical channels of the input signal 11.

In the operation of the addition filter 120, the first port 101 of the circulator 12 receives the addition optical signal 102 to be added to the input signal 11. The addition signal 102 may include, for example, a plurality of optical channels centered on wavelengths λ ₁ , λ ₂ ,..., Λ _N to be added to the input signal 11. The addition signal 102 is transmitted to the circulator 13 through the optical fiber 103, and then sends the addition optical signal 102 clockwise to the second port of the circulator. The additive optical signal 102 is present in the second port 104 and propagates through the optical fiber 105 to the grating element 14 of the grating unit 10. At least one grating element 14 is tuned to reflect in at least one optical channel of the addition signal 102. For example, one grating unit 10 may be tuned to reflect an optical channel centered on wavelength λ ₂ to provide a filtered addition signal 109. The other grating element is tuned or parked to pass the remaining optical channel of the additive optical signal 102.

The filtered addition signal propagates backwards to the second port 104 of the circulator 13 and then through the optical fiber 108 to the third port of the circulator 13 to provide the filtered addition signal 109. 107 sends the combined light. Thereafter, the output signal 109 is transmitted to the input port of the optocoupler 121. The input signal 11 having the optical channel centered on the wavelengths λ ₁ , λ ₂ ,..., Λ _N is transmitted to the second input port of the optical coupler 121. The optocoupler 12 combines the filtered addition signal 109 and the input signal 11 and includes a combined optical signal including a plurality of channels centered on wavelengths λ ₁ , λ ₂ ,..., Λ _N. (122) to the output port of the coupler.

While the addition filter 120 of FIG. 7 adds a single channel to the input light 11, one of ordinary skill in the art is provided with one or more optical signals added, and the addition filter is provided with a corresponding number of grating units. (10) or it will be appreciated and admitted that it has a single grating unit with sufficient bandwidth to reflect the adjacent optical channels to be added.

Referring to FIG. 8, since the tunable add filter 130 is the same as the tunable add filter 110 of FIG. 6, the same components are denoted by the same reference numerals. The tunable addition filter 130 includes a plurality of tunable Bragg grating units 10 optically connected in series to the ports of an optical directing device 131 such as an optocoupler. Since each grating unit 10 is operated to compress each grating element 14, it is tuned or parked to pass the desired optical channel to be added to the optical input signal 11.

In the operation of the addition filter 110, the addition signal 115 may include a plurality of optical channels centered on the wavelengths λ ₁ , λ ₂ ,..., Λ _N that should be added to the input signal 11, for example. have. The addition signal 115 is transmitted to the grid element 14 of the grid unit 10 through the optical fiber 116. Each grating unit 10 is tuned or parked to pass a selected optical channel of the addition signal 115 to be added to the input signal 11. For example, each grating unit 10 may be tuned to pass an optical channel at a wavelength λ ₂ to provide a filtered addition signal 132. Thereafter, the filtered addition signal 132 is transmitted to the input port of the optical coupler 131 through the optical fiber 114. The optocoupler 131 combines the filtered addition signal 132 and the input signal 11 and includes a combined optical signal including a plurality of channels centered on wavelengths λ ₁ , λ ₂ ,..., Λ _N. 133 is provided to the output port of the optocoupler 131.

While the addition filter 130 of FIG. 8 adds a single channel to the input light 11, one of ordinary skill in the art will appreciate and appreciate that one or more optical signals are added.

FIG. 9 shows a reconfigurable optical add / drop multiplexer (ROADM) 140 that effectively combines the tunable drop filter 80 of FIG. 3 and the tunable add filter 100 of FIG. 5, as described above. The grating unit 10 is used to drop the selected optical channel and add the selected optical channel. Components such as the drop filter 80 of FIG. 3, the add filter 100 of FIG. 5, and the ROADM 140 of FIG. 9 are denoted by the same reference numerals.

As shown in FIG. 9, the pair of grating units 10 is tuned to reflect the optical channel centered on the wavelengths λ ₂ , λ ₃ , while the other grating units are wavelengths λ ₁ , λ ₄ ,..., Λ _N ), tuned to pass the rest of the channel centered. Therefore, the ROADM 140 drops the optical channel centered on the wavelengths λ ₂ and λ ₃ , and adds the addition optical signal 102 having the channel centered on the wavelength λ ₂ . Therefore, the output signal 109 includes an optical channel centered on the wavelengths λ ₁ , λ ₂ , λ ₄ ,..., Λ _N.

FIG. 10 shows a reconfigurable optical add / drop multiplexer (ROADM) 150 that effectively combines the tunable drop filter 80 of FIG. 3 and the tunable add filter 110 of FIG. 6, wherein the add filter 110 is a drop. It is optically connected in series with the filter 80. As described above, the drop filter 80 and the add filter 110 function almost the same. Components such as the drop filter 80 of FIG. 3, the add filter 110 of FIG. 6, and the ROADM 150 of FIG. 10 are denoted by the same reference numerals.

As shown in FIG. 10, the pair of grating units 10 of the drop filter 80 are tuned to reflect the optical channel centered on the wavelengths λ ₂ and λ ₃ , while the other grating unit is tuned to the wavelengths λ ₁ ,. tuned to pass the remaining channels centered on λ ₄ ,..., λ _N ). The grating unit 10 of the addition filter 110 is tuned to pass the addition signal 115 having an optical channel centered on the wavelength λ ₂ . Accordingly, the ROADM 150 drops the optical channel centered on the wavelengths λ ₂ and λ ₃ , and adds the addition optical signal 115 having the channel centered on the wavelength λ ₂ . Therefore, the output signal 119 includes an optical channel centered on wavelengths λ ₁ , λ ₂ , λ ₄ ,..., Λ _N.

11 shows a reconfigurable optical add / drop multiplexer (ROADM) 160 that effectively combines the tunable drop filter 90 of FIG. 4 and the tunable add filter 100 of FIG. 5, with the add filter 100 being a drop. It is optically connected in series with the filter 90. As described above, the drop filter 90 and the add filter 100 function almost the same. Components such as the drop filter 90 of FIG. 4, the add filter 100 of FIG. 5, and the ROADM 160 of FIG. 11 are denoted by the same reference numerals.

As shown in FIG. 10, each grating unit 10 of the drop filter 90 is tuned to pass through an optical channel centered on the wavelengths λ ₂ and λ ₃ , while the other grating unit is tuned to a wavelength λ ₁ ,. tuned to reflect the remaining channels centered on λ ₄ ,..., λ _N ). The grating unit 10 of the addition filter 100 is tuned to reflect the addition signal 102 having an optical channel centered on the wavelength λ ₂ . Therefore, the ROADM 160 drops the optical channel centered on the wavelengths λ ₂ and λ ₃ and adds the addition optical signal 102 having the channel centered on the wavelength λ ₂ . Therefore, the output signal 108 includes an optical channel centered on wavelengths λ ₁ , λ ₂ , λ ₄ ,..., Λ _N.

FIG. 12 shows a reconfigurable optical add / drop multiplexer (ROADM) 170 that effectively combines the tunable drop filter 90 of FIG. 4 and the tunable add filter 110 of FIG. 6, wherein the add filter 110 is a drop. Optically connected in series with the filter 90. As described above, the drop filter 90 and the addition filter 110 function almost the same. Components such as the drop filter 90 of FIG. 4, the add filter 110 of FIG. 6, and the ROADM 170 of FIG. 12 are denoted by the same reference numerals.

As shown in FIG. 12, each grating unit 10 of the drop filter 90 is tuned to pass through an optical channel centered on the wavelengths λ ₂ and λ ₃ , while the other grating unit is tuned to a wavelength λ ₁ ,. tuned to reflect the remaining channels centered on λ ₄ ,..., λ _N ). Each grating unit 10 of the addition filter 110 is tuned to pass an addition signal 115 having an optical channel centered on the wavelength λ ₂ , while the other grating unit is tuned to wavelengths λ ₁ , λ ₄ , ..., λ _N ) to tune to reflect the remaining channels centered. Therefore, the ROADM 170 drops the optical channel centered on the wavelengths λ ₂ and λ ₃ , and adds the addition optical signal 115 having the channel centered on the wavelength λ ₂ . Therefore, the output signal 119 includes an optical channel centered on wavelengths λ ₁ , λ ₂ , λ ₄ ,..., Λ _N.

FIG. 13 shows a reconfigurable optical add / drop multiplexer (ROADM) 170 which is similar to the ROADM 160 of FIG. 12, which is tunable with the tunable drop filter 90 of FIG. 4. The adder filter 110 is effectively combined. Effectively, a single four-port circulator 181 replaced the pair of three-port circulators 12 and 13 in ROADM. As described above, ROADM 180 of FIG. 13 performs almost the same operation as ROADM 170 of FIG. Components such as the drop filter 90 of FIG. 4, the add filter 110 of FIG. 6, and the ROADM 170 of FIG. 12 are denoted by the same reference numerals.

In addition to the above embodiments of ROADM, the present invention also includes any one of the tunable drop filters 80 and 90 of FIGS. 3 and 4 and any one of the tunable addition filters 120 and 130 of each of FIGS. 7 and 8. By optically connecting in series in several combinations with, other ROADM configurations can also be expected.

While the grating unit 10 is connected to each other in a four-port circulator, it is understood that any other optical directing device or means is used in place of the circulators 12, 13, such as optocouplers, optical splitters or free spaces. Everyone will admit that they are in range.

The scope and geometry of any embodiment described herein is for illustrative purposes only, and any other scope, if desired, may be used depending upon the application, size, performance, and manufacturing requirements in view of the teachings herein.

Although the present invention has been described in connection with various specific embodiments, the present invention is not limited thereto, and various modifications can be made without departing from the spirit of the invention.

Claims (31)

An inner core disposed within the outer cladding, and a grating disposed within the inner core and reflecting a first reflected wavelength of light backwards along the inner core and propagating the remaining wavelengths of light therethrough and having a pair of opposing surfaces Optical waveguide, A compression tuning optics having a compression device for compressing opposing surfaces facing each other to tune the grating to vary the reflected wavelength of light reflected backwards along the inner core; An optical directing device for providing the compression tuning optical device with an input optical signal having a plurality of optical channels centered at a constant interval of wavelength, And said compression tuning optics remove optical channels from said input optical signal. The optical drop filter according to claim 1, further comprising a plurality of compression tuning optics optically connected in series. 2. The optical drop filter of claim 1, wherein the compression tuning optics is dynamically tuned to reflect at least one optical channel removed from the input optical signal and to pass the remaining optical channel of the input optical signal. . 2. The optical drop filter of claim 1, wherein the compression tuning optics are dynamically tuned to pass through at least one optical channel removed from the input optical signal and to reflect the remaining optical channel of the input optical signal. The optical drop filter according to claim 1, wherein the optical waveguide has an outer dimension along the vertical axis and the transverse direction, and the outer dimension is at least 0.3 mm along the transverse direction. 2. An optical drop filter according to claim 1, wherein at least a portion of the optical waveguide is adjacent and has a transverse cross section of substantially the same material. 7. An optical drop filter according to claim 6, wherein the same kind of material is made of glass material. The optical drop filter according to claim 1, wherein the optical waveguide is a cane. The optical drop filter of claim 1, wherein at least a portion of the optical waveguide is generally cylindrical in shape and has a diameter of at least 0.3 mm. 2. An optical drop filter according to claim 1, wherein the grating has a characteristic wavelength and the optical waveguide is shaped to provide a shift in wavelength due to a change in force with respect to the optical waveguide. The optical drop filter according to claim 10, wherein the optical waveguide has a shape of a dog bone. The optical drop filter of claim 1, wherein the compression device comprises an actuator for applying a compressive force along an axis with respect to at least one opposing surface of the optical waveguide. The optical drop filter according to claim 1, wherein the external dimension of the optical waveguide along the axial direction is larger than the external dimension of the optical waveguide along the transverse direction. The optical drop filter of claim 1, wherein the inner core is a single mode core. The optical drop filter according to claim 1, wherein the compression tuning optics manually tunes the optical waveguide in response to a change in temperature to maintain the reflected wavelength over a predetermined temperature range. An inner core disposed within the outer cladding, and a grating disposed within the inner core and reflecting a first reflected wavelength of light backwards along the inner core and propagating the remaining wavelengths of light therethrough and having a pair of opposing surfaces Optical waveguide, A compression tuning optics having a compression device for compressing opposing surfaces facing each other to tune the grating to vary the reflected wavelength of light reflected backwards along the inner core; An optical directing device optically connected to said compression tuning optics, said optical directing device for combining an added optical channel with an input optical signal having a plurality of optical channels centered at constant intervals, And an optical channel coupled to the input optical signal to provide an output signal coupled to the compression tuning optics. 17. The optical addition filter as set forth in claim 16, further comprising a plurality of compression tuning optics optically connected in series. 17. The optical addition filter of claim 16, wherein the compression tuning optics are dynamically tuned to reflect at least one optical channel added to the input optical signal and to pass the remaining optical channels of the input optical signal. . 17. The optical addition filter of claim 16, wherein the compression tuning optics is dynamically tuned to pass through at least one optical channel added to the input optical signal and to reflect the remaining optical channel of the input optical signal. 17. The optical adding filter of claim 16, wherein the optical waveguide has an outer dimension along the vertical axis and the transverse direction, the outer dimension being at least 0.3 mm along the transverse direction. 17. The optical addition filter of claim 16, wherein at least a portion of the optical waveguide is adjacent and has a transverse cross section of substantially the same material. 22. The optical addition filter of claim 21, wherein the same kind of material is made of glass material. 17. The optical addition filter of claim 16, wherein the optical waveguide is a cane. 17. The optical adding filter of claim 16, wherein at least a portion of the optical waveguide is generally cylindrical in shape and has a diameter of at least 0.3 mm. 17. The optical addition filter of claim 16, wherein the grating has a characteristic wavelength and the optical waveguide is shaped to provide a shift in wavelength due to a change in force with respect to the optical waveguide. 27. The optical adding filter of claim 25, wherein the optical waveguide has a shape of a dog bone. 17. The optical adding filter as claimed in claim 16, wherein the compression device is provided with an actuator for applying a compressive force along an axis with respect to at least one opposing surface of the optical waveguide. 17. The optical addition filter of claim 16, wherein an outer dimension of the optical waveguide along the axial direction is greater than an outer dimension of the optical waveguide along the transverse direction. 17. The optical addition filter of claim 16, wherein the compression tuning optics manually tunes the optical waveguide in response to a change in temperature to maintain the reflected wavelength over a predetermined temperature range. An inner core disposed within the outer cladding, and a grating disposed within the inner core and reflecting a first reflected wavelength of light backwards along the inner core and propagating the remaining wavelengths of light therethrough and having a pair of opposing surfaces Optical waveguide, A compression tuning optics having a compression device for compressing opposing surfaces facing each other to tune the grating to vary the reflected wavelength of light reflected backwards along the inner core; A first optical directing device for combining an added optical channel with an input optical signal having a plurality of optical channels centered at wavelengths which are optically connected to the compression tuning optical device and having a constant interval, And an optical channel coupled to the input optical signal to provide an output signal coupled to the compression tuning optics. A compression force assembly for providing a compression force applied along the axis of compression, Grating compression responsive to the optical input signal and the compression force to provide a grating compression unit optical signal having a grating along the axis of compression in response to the optical input signal and having a selected wavelength of a channel added to or dropped from the input signal Compression tuned optical add / drop module with unit.