CN1314598A

CN1314598A - Controllable wave length selective light cross connector

Info

Publication number: CN1314598A
Application number: CN 00102244
Authority: CN
Inventors: 莫哈木德·T·法特西; 桑霍·金; 韦恩·哈威·诺克斯; 哈里施·马沃里
Original assignee: Lucent Technologies Inc
Current assignee: Nokia of America Corp
Priority date: 2000-02-18
Filing date: 2000-02-18
Publication date: 2001-09-26
Anticipated expiration: 2020-02-18
Also published as: CN1221824C

Abstract

Light crosslinking exchanger includes light router to distribute mulitiple wavelength input light signals, light combiner in the outer port of the exchanger to output multiple wavelength light signals; and optical fiber to interconnect the light router and light combiner. The selected optical fiber incldues controllable wavelegnth selecting element, such as magnetic controlled fiber grating capable of permitting light signal is several channels to pass through, so that some selected channel in specific wavelength can be transmitted from any input ports of the exchanger to any output port.

Description

Controllable wave length selective light cross connector

The present invention relates to the optical cross-connect of route multiple wavelength optical signal, specifically, but relate to the magnetic control wave length selective light cross connector.

In modern telecom network, because the high speed and the wide bandwidth of optical fiber, general first-selected optical fiber is made transmission medium.Wavelength-division multiplex (WDM) combines many wavelength optical signals, transmits on an independent optical fiber, thereby is used to satisfy the higher and wideer requirement of bandwidth of growing speed.

In communication network, adopt in the network of WDM such as those, each light signal needs and selectively routes to different destinations.By the interconnecting nodes in the communication network, a kind of necessary parts of route signal are the matrix or the cross connection interchanger of a high power capacity selectively.At present, the most of cross connection interchangers that in optical communication network, use be not manual be electronics.Electronic exchanger requires a plurality of light-electricity and electrical-optical conversion.Because the form with light transmits information, beneficial on speed and bandwidth, so to the optical-fiber network based on WDM, the network element of full light is first-selected solution.In addition, on the dirigibility that managing bandwidth is provided on the optical layers (for example on the basis at wavelength one by one), also need the network element of full light.

The cross-connect and the interchanger of the full light of development though made an effort, these effort fail to catch up with the requirement of and eternal growth that bandwidth wideer higher to speed.For example, some cross connection device is planned lithium niobate (LiNbO ₃) interchanger array and fiber amplifier combine, to solve the speed and the loss problem of existing system.Though lithium niobate interchanger array has the performance of quick exchange device, fiber amplifier has can compensate LiNbO ₃The characteristic of loss, but this class cross-connect does not possess the necessary wavelengths selectivity, so that bandwidth is effectively managed.In another kind of optical cross connection device, use Wavelength conversion element, each wavelength channel is rearranged according to common destination.Particularly, multiple wavelength optical signal become each wavelength optical signals, and each light signal is used then each layer exchanger arrangement that separates with the corresponding space of each different wave length to transfer by shunt.The exchanger arrangement layer that uses shunt and separate, this cross connection device implements not only costliness but also complexity.Similarly, known other uses the cross connection device of multistage exchanger arrangement type, and be expensive and complicated too.

According to a kind of optical cross connect interchanger of the present invention (switch), comprise an optical router that distributes the multi-wavelength light input signal, one multi-wavelength signals delivered to the optical combiner of this interchanger delivery outlet, and the optical fiber of optical router and optical combiner interconnection.Selected interconnection fabric comprises controlled wavelength and selects element, but magnetic control fiber grating for example, this grating sees through or the interior separate channel of reflection multiple wavelength optical signal, makes a selecteed specific wavelength channel, can route to any delivery outlet from any input port of this interchanger.

In one exemplary embodiment, optical router partly comprises a plurality of input photo-couplers, and wherein each input photo-coupler links to each other with the corresponding input port of this optical exchanger.Equally, optical combiner partly comprises a plurality of output optical couplers, and wherein each output optical coupler links to each other with the corresponding delivery outlet of this optical exchanger.Each input photo-coupler is together with the fiber grating on interconnection fabric that is attached thereto, be used to distribute the signal that receives through the input port, and each output optical coupler is used to make up the signal that will deliver to this interchanger delivery outlet together with the fiber grating that is attached thereto.By seeing through and reflective mode operation of control fiber grating, the switching of each channel that can improve multiple wavelength optical signal with fiber grating on wavelength basis one by one.

The optical cross connect interchanger does not also require that light arrives electricity and electric conversion to light, and only the form with light transmits information, thereby can obtain the associated advantage on speed and bandwidth.In addition, owing to use a series of high speeds, but but the fiber grating of magnetic tuning and magnetic latch is realized signaling transfer point, this optical exchanger has possessed the necessary wavelengths selectivity, has optimized the management of bandwidth on optical layers, such as wavelength management one by one.Compared with existing apparatus, this optical exchanger is so not expensive and so not complicated yet.Its moves fast and need not power and keeps the switching state.Also have, can assemble and encapsulate this interchanger, make its exchanger performance and wavelength selectivity not be subjected to the influence of variation of ambient temperature by certain mode.

After the detailed description of investigation below in conjunction with accompanying drawing, can obtain the more complete understanding of the principle of the invention, represent components identical with identical reference number in the accompanying drawing.Accompanying drawing has:

Fig. 1 is an exemplary embodiment, and 2 * 2 wavelength selective light interchangers according to the principle of the invention draw;

A kind of exemplary magnetic tuning fiber bragg grating device but Fig. 2 schematically draws, its continuously-tuning and breech locked are on several wavelength value;

Fig. 3 (a)-(c) rectangle that draws is respectively optimized crooked and excessively crooked M to the H magnetic hysteresis loop;

Fig. 4 draws by the drift experimental data of breech lock wavelength, and data are the fiber gratings to a continuously-tuning, and the pulsed magnetic field that applies varying strength obtains.

Fig. 5 is a synoptic diagram, but bistable magnetic tuning fiber bragg grating device of expression;

The repeatable experimental data that Fig. 6 draws two wavelength, but it is that the magnetic field that applies contrary sign obtains to a bistable magnetic tuning device;

A kind of variation that Fig. 7 (a)-(b) draws device architecture, but it utilizes the magnetic control bending of the optical fiber that contains grating, makes fiber grating obtain certain strain;

Fig. 8 (a) is another exemplary embodiment, and another 2 * 2 wavelength selective light interchangers according to the principle of the invention draw;

Fig. 8 (b) is the synoptic diagram of a simplification, and the illustrative example that draws shows the principle of work of 2 * 2 wavelength selective light interchangers shown in Figure 2;

Fig. 9 is an exemplary embodiment, the K according to the principle of the invention that draws * M wavelength selective light cross connection device;

Figure 10 (a) draws in K * M wavelength selective light cross connection device of Fig. 91 * M optical wavelength selection by the device part;

Figure 10 (b) K * 1 wavelength selective light combiner part in K * M wavelength selective light cross connection device of Fig. 9 of drawing;

Figure 11 shows a kind of cheapness and practical method, (a) but the magnetic control grating, or (b) overall optical cross connect system is encapsulated in the single constant temperature oven, to resist the fluctuating of environment temperature, makes it stable.

Figure 12 (a)-(b) is a synoptic diagram, show a bistable, but the magnetic tuning grating device by adding a negative expansion element, makes it to temperature-insensitive.

Should be understood that these figure only are used for notion of the present invention is described, except that curve map, all is that not to scale (NTS) is drawn.

The present invention is divided into four parts.I is partly described according to an optical cross connect interchanger of the present invention.But II is partly described the structure and the principle of work of the magnetic tuning grating that is used for this interchanger.III is partly described the embodiment and the IV of the various variations of the interchanger of being invented and is partly described the device that encapsulates this interchanger.

I. the optical cross connect interchanger

Referring to accompanying drawing, the exemplary embodiment that Fig. 1 draws one 2 * 2 optical exchanger 100, this interchanger can transfer multiple wavelength optical signal, for example each channel of wavelength-division multiplex (WDM) light signal.In example shown in Figure 1, multi-wavelength signals I ₁And I ₂, each with Expression comprises N individual channel, and wherein one of each individual channel and N wavelength interrelates.But be noted that this configuration is only in order to illustrate.For example, can be assigned to multi-wavelength signals I to different wave length ₁And I ₂Each channel.

Optical exchanger 100 comprises an optical router part 150 and an optical combiner part 151.Comprise that directional light transmits the optical router part 150 of

device

101 and 102, to multi-wavelength light input signal I ₁And I ₂Distribute.Comprise that directional light transmits the optical combiner part 151 of

device

103 and 104, combines multiple wavelength optical signal, as output signal O ₁And O ₂And export.Say that more specifically directional light transmits

device

101 and 102 and receives multi-wavelength light input signal I through input

optical fibre

106 and 107 respectively ₁And I ₂Equally, directional light transmits

device

103 and 104 and is coupled with output

optical fibre

108 and 109 respectively, sends multi-wavelength light output signal O respectively ₁And O ₂Directional light transmits device 101-104 can comprise the optical circulator that the insider knows, or any can be with other known device of oriented approach transmission or coupling light energy.For ease of explanation, explanation after this all refers to optical circulator 101-104.

Optical circulator 101-104 is coupled through interconnection fabric 125-128, and wherein optical fiber 125-126 is equipped with wavelength within it to select the wavelength of element 105 to select optical fiber.Wavelength selects the element 105 can be by the tunable fiber Bragg grating of knowing in the industry, or any other known wavelength selective filters constitutes.For ease of explanation, explanation after this all refers to fiber grating 105.As shown in the figure, optical fiber 125 comprises fiber grating 105A, and optical fiber 126 then comprises fiber grating 105B.As shown in the figure, the mouth 110 of optical circulator 101 is selected optical fiber 125 through wavelength, along mouth 115 couplings of through path and optical circulator 103.The mouth 111 of optical circulator 101 is through optical fiber 127, along mouth 118 couplings of bridged path and optical circulator 104.Equally, the mouth 113 of optical circulator 102 is selected optical fiber 126 through wavelength, along mouth 117 couplings of through path and optical circulator 104.The mouth 112 of optical circulator 102 is through optical fiber 128, along mouth 116 couplings of bridged path and optical circulator 103.

Different with existing optical exchanger and cross connect system, optical exchanger 100 according to the principle of the invention, uses tunable fiber grating to realize wavelength selection signaling transfer point.Particularly, fiber grating 105 can be tuning, from multi-wavelength light input signal I ₁And I ₂In, reflection or see through the optical channel of any specific wavelength.In an example, fiber grating 105 can be tuning or programming, makes that at least one is used to certain is wanted the specific wavelength of route in the fiber grating 105, routes to certain output from certain input of optical exchanger 100.Fiber grating 105 both can be used as rejection filter, also can be used as bandpass filter.During as rejection filter, fiber grating 105 can be used for reflecting any specific wavelength or one group of wavelength in the multiple wavelength optical signal.Otherwise during as bandpass filter, fiber grating 105 can be used for seeing through any specific a wavelength or one group of wavelength.

Utilize manufacturing technology to assemble the method for fiber grating, or tuning/programming technique, be well-known.In the embodiments described herein, fiber grating can be access in fiber path, or directly is etched on the optical fiber, or adopts other known technologies.Relevant to the further rudimentary knowledge of fiber grating as the wavelength alternative pack, for example with reference to Strong Bragg Gratingsin Non Sensitized Low Loss Planar Waveguides as Building Biocks forWDM Network Components such as Hubner, SPIE Vol.2998, No.12, Photonics West 97, San Jose, CA, 1997.

Be in operation, branch/slotting principle that optical exchanger 100 adopts wavelength to select is finished the signaling transfer point with traditional crossbar switch equivalence.More specifically say comprise each channel, and each channel has a multiple wavelength optical signal of its specific wavelength, as input I ₁, deliver to optical circulator 101 from optical fiber 106.Optical circulator 101 is sent to the mouth 110 of multiple wavelength optical signal through optical circulator 101 wavelength and selects path 125.Those have each channel of wavelength in fiber grating 105A transmission band, connect as a kind of " leading directly to ", and as the part of multi-wavelength output signal O1, are transferred into the mouth 115 of optical circulator 103.This " leading directly to " formula route is exactly the operation equivalent with the horizontal state (bar state) of crossbar switch.Each channel that those have wavelength in the fiber grating 105A zone of reflections, be reflected back toward optical circulator 101 the mouth 110.Then, these channels through cross-over connection optical fiber 127, are routed the mouth 118 to optical circulator 104 from the mouth 111 of optical circulator 101, and as multi-wavelength output signal O ₂A part and be sent.In fact, improve the cross connection of those channels that are reflected with fiber grating 105A, the vertical state (cross state) when its mode connects signal cross with crossbar switch is identical.The identical operations principle can be used for entering the light signal I of optical circulator 102 ₂On, for simplicity, no longer repeat at this.

As shown in the figure, what think over is, can control the fiber grating that each is selected, so that to each channel in the multiple wavelength optical signal, carries out suitable " leading directly to " route and " cross connection " route.Fig. 1 a kind of possible control device of drawing, in view of the above, by a single controller 120, with an interlock interchanger 121-122 of mechanism, control fiber grating 105A.Particularly, can control the fiber grating 105A of optical fiber 125 and the fiber grating 105B of optical fiber 126 simultaneously with interchanger 121, can also control another fiber grating 105A of optical fiber 125 and another fiber grating 105B of optical fiber 126 simultaneously with interchanger 122, so analogize.In this example, two multiple wavelength optical signal I ₁And I ₂Each channel can therefore can advantageously use this controlling schemes with each identical wavelength, with the channel of the corresponding wavelength that guarantees every optical fiber carrying, realize synchronous switching, avoid the interference between any two same wave long channels in same optical fiber.

Tunable fiber grating 105 can be accessed individually, subsequently in addition suitably control (promptly controlled separately).Appropriate control measure can comprise, the technology of utilizing the insider to know, tuning individually (or programming) every optical fiber, or individually and selectively its see through and the reflection running status between conversion (for example realizing the ON/OFF effect).Specifically, grating can thermal tuning, piezoelectricity is tuning, magnetostrictive tuning (see and be presented to people's such as A.M.Glass U.S. Patent No. 5,812,711 in September 22 in 1998) or magnetic tuning (are seen the U.S. Patent No. 5 that July 14 in 1998 was presented to people such as S.Jin, 781,677).In these technology, believe magnetic tuning the most usefully to the application.

But II. be used for the magnetic tuning fiber grating of this interchanger

Referring to accompanying drawing, the fiber bragg grating device 10 of an exemplary recombinant but Fig. 2 schematically draws, it is made up of one section optical fiber 11 that comprises refractive index perturbation grating 12.With cementing agent 13 or mechanical fixation, optical fiber firmly is fixed between magnet 14 able to programme and the guide housing 16, so that the magnetic force of magnet 14 is sent to grating 12 in the zone of grating.With being bonded at the second block magnet 15 of cover on 16 to magnet 14 application of forces.Magnet can be the guidepost shape, but the shape of noncircular cross section preferably, so that handling or reversing of optical fiber reduced to minimum during work.One or more electromagnet (solenoid) 17 next-door neighbour's magnet are placed, and a controlled magnetic field is provided between magnet.Guide housing 16 is a pipe preferably, but also other shape can be arranged, for example, it can by U-shaped last slice and following sheet two parts assemble.

Guide housing 16 is made tubulose with glass, quartz, metal or plastics usually.Fiber grating or use mechanical fasteners, or with bonding, such as with epoxy resin or scolder, make it attached on magnet 14 and the guide housing 16.As use scolder, optical fiber surface will apply the layer of metal layer, to improve the cohesive strength of scolder.Here with this bonding of bonding agent 13 expressions.

As shown in Figure 2, adjust magnet 14,15, making has a little air-gap between them.Extremely adjacent (S is close to N) that their orientation is preferably opposite, and the field of electromagnet 17 will produce a drawing stress on grating.Preferably not affined with the magnet 14 of guide housing 16 bonding, such as with a block 18.Relate to magnet length (magnet 15) variation in order to eliminate, cause changes of voids between two magnet, and then the thermal expansion of magnetic force and fiber stress variation, the bonding position of magnet cover is as far as possible near air-gap, bonding point is less than 5% of magnet length to the distance in space, and is better less than 2%.

During operation, reach the magnetic force of grating, make grating produce strain, change the wavelength response of grating from magnet 14,15 and 17.Power between two magnet that attracts mutually, approximate be proportional to magnetic induction (M) square multiply by xsect (A) (the F ∝ M of magnet in the gap ²* A).Therefore, stronger magnet (higher M) or bigger magnet (bigger A) provide stronger power.Yet the strong magnet of high coercivity is difficult to programming or tuning.Elongate or compression for example during 1% (ε=Δ l/l=0.01) when the length of fiber grating, the cycle ∧ of grating also will change.But because interatomic disance also is subjected to the influence of elastic stress in the glass, thereby its refractive index also changes, and is 1% so the change of resonance bragg reflection wavelength is inaccurate.This stress of refractive index can be used photoelastic constant P _εExpression is to SiO ₂Optical fiber, its representative value is about 0.22.The strain stress (ε=Δ l/l) that is applied by magnetic causes the change of wavelength to can be expressed as Δ λ/λ=(Δ l/l) (1-P _ε)=ε (1-P _ε).This strain stress is determined by stress that applies (σ) and elastic modulus (E), ε=σ/E, and the stress on optical fiber is that power (F) is divided by cross-sectional area (π r ²), r is the radius of fiber grating here.Put these equations in order,, Δ λ/λ=(F/ π r ²) (1/E) (1-P _ε).For example, to λ=1550nm, F=1200gm, providing the mobile of wavelength is Δ λ=16.01nm, or about 1% change.To being spaced apart the wavelength division multiplexed channel of 0.8nm, the Δ λ of generation is enough to change filtered wavelength on 20 channel spans.

Because optical fiber can rupture less than about 6% o'clock in tensile strain, also because this inefficacy is catastrophic, thereby the design of extremely wishing adjustable grating can provide a upper limit of total tensile strain automatically.The structure of Fig. 2 device just provides this advantage, because default space can be used as this upper limit between two magnet.When optical fiber extends because of magnetic force and magnet when finally contacting with each other, optical fiber can not extend again.Space Len req (upper limit of elongate optical fiber) between two magnet of Fig. 2, usually less than the length at the optical fiber place of being stretched 4% (for example 2 " the long optical fiber that contains grating; the space should set～80mil is following), best less than 2% of the fiber lengths that contains grating.Back one numerical value is equivalent to 1/3rd of fibercuts strain.

Be sure of that fiber grating does not suffer twist distortion, this also is crucial, because distortion can reduce the fracture strength of optical fiber under given tensile strain, and can make the light signal distortion.For eliminating or reducing twist distortion, the guiding mechanism of magnet is set, be under the situation of circle in container section, add guided way, or use noncircular vessel, side can not rotate when removable magnet was moved.

Fig. 3 a, 3b and 3c draw the M of the three kind dissimilar magnet relevant with the present invention quantitatively to the H magnetic hysteresis loop.But a significant advantage of recombinant grating device is will keep the grating cycle variation of generation, thereby its wavelength variations to need not to apply lasting power.Because the breech locked of the magnetic force of rectangular loop magnet 14,15, this is possible.This device can be done bistable between two wavelength tuning.Height anisotropy and adjust its magnetized axis and make it a kind of magnetic material parallel with optical axis has the rectangular hysteresis loop shown in Fig. 3 a.See IEEE Trans.Magn. such as Jin, MAG-23, No.5, P.3187 (1987), this literary composition is taken in here, for your guidance.With through the aging Fe-Cr-Co alloy of deformation,, be comparatively satisfied as magnet with this loop shape.

With magnet with rectangular hysteresis loop, can make the device of bistable strain, it is changed between two wavelength: for example, the bragg reflection wavelength λ of zero strain ₀With saturated strain reflected wavelength lambda ₁Apply an AC demagnetization magnetizing field, obtain λ ₀DC pulse current with being enough to make magnet saturated obtains λ ₁The advantage of bistable device is to have reduced adding electric current or to the susceptibility of stray magnetic field.

To the continuous tuning of wavelength, fibre strain becomes rectangular loop to the characteristic curve that applies magnetic field, and this is not always required, because among Fig. 3 a, for example when the many channels of tuning leap, and during target to be certain placed in the middle strain, the edge that curve is precipitous can cause control problem.For being easy to control the strain in the fiber grating, M-H and ε-H loop line can tilt by image pattern 3 (b) like that.Increase the self-demagnetization field of magnet, for example or increase the electromagnet effective diameter, perhaps reduce its length, thereby reduce the length over diameter ratio of magnet, just can realize the inclination of loop line.The inclination of loop line the best is shown in Fig. 3 (b), promptly, after remove in the magnetic field that applies, remaining magnetization or remaining fibre strain still possess goes up identical with saturation value (at least 90%), and when field-reversed, fast M that increases or field of ε, when beginning near null field, satisfaction is in coercitive 30% scope, at coercive force (H _c) 10% scope in better.M-H and ε-H loop line too tilts, and as Fig. 3 (c), is undesirable, descends because this situation causes the breech locked performance of strain in the grating.The degeneration of this breech locked strain is pointed out with arrow among Fig. 3 (a).

Be an example that loop line is tilted below.With a kind of Fe-28%Cr-7%Co alloy, aging to produce a H through deformation _cBe the rectangle M-H loop line of 70Oe, size is 0.180 " diameter and 4 " cause the inclination of M-H loop line, obtain being similar to Fig. 3 (b) M-H loop line with～60Oe when long.

But the magnetic tuning of construction drawing 2 and the fiber grating of breech locked preferably, more desirable installation step is as follows.The first step is assembled the step of this tunable optical gate device, provides a fiber grating, Bragg grating for example, and it has the bragg reflection wavelength that needs, so that tell or wavelength component of slotting λ.For example, to the light beam of central wavelength 1550nm, with SiO ₂In the optical fiber for the basis (refractive index n～1.45), the Bragg grating cycle, ∧ was 500nm..But put into each the fiber grating length in the magnetic tuning grating assembly, usually in 5mm to 200mm scope, better in the 10-100mm scope.To short fiber grating, the conventional fiber part outside the grating can be used for or be bonded on the magnet assembly, perhaps is bonded on the guide housing (or substrate).

Next step is that magnet assembly and guide housing are bonded on the fiber grating.At least need two magnet assemblies, can be two independent, also can be altogether.Their magnetic pole orientation preferably is parallel to the optical axis of fiber grating.In adjustable grating of the present invention, at least a portion of each magnet assembly is permanent magnet semihard or the band remanent magnetization.But the intensity that has a magnet at least, the magnetic field that applies by change, but be that sassafras able to programme removes and Reprogrammable.When this two magnet with opposite magnetic pole relative to each other the time, for example the arctic is facing to the South Pole, they are just attracted each other.Be bonded in one of magnet and be subjected to drawing stress with fiber grating on the guide housing, its tensile elasticity strain stress with the increase of stress σ increase with being directly proportional (ε=σ/E, here to quartz glass, elastic modulus E=1.5 * 10 ⁶Psi).

The 3rd step was to aim at and grating is bonded on one of magnet and the guide housing.Guarantee bonding intensity and make on the adhesive surface strain relief reduce to minimum, require to use the strong non-thermal plasticity bonding agent of mechanicalness, the perhaps all relative high scolder of fusing point, physical strength and creep resistance.The optical fiber surface that bonds need apply a metal layer, with the bond strength of improvement with scolder.

To the magnet of given volume, in order to make the magnetic force maximum, the space of relative two interpolars is very little.The space increases, and magnetic force reduces.The space requires less than about 80mil.More preferably, the space is set at, make that the maximum tension strain is maintained at about in the fiber grating～2% or littler, minimum is reduced in the danger of fibercuts like this.

More desirable ferromagnetic material is the magnetic material that those its magnetic properties are changed by pulsed magnetic field.Suitable magnet example such as Fe-Cr-Co, Fe-Al-Ni-Co (alnico alloy), Cu-Ni-Fe (magnetoflex), Co-Fe-V (Vicalloy), through special processing, low-coercivity (H _c) Rare-Earth Cobalt (Sm-Co) or Nd-Fe-B magnet and barium ferrite or strontium ferrite magnet.The coercivity scope of magnet able to programme usually requires below 500Oe, and below 100Oe better, be easy to magnetize again and programme with solenoidal pulsed field.Coercivity more than 10Oe, better, so that keep the stable of remanent magnetization, also is convenient to resist the demagnetization of stray magnetic field usually more than 30Oe.After removed in magnetic field, for the breech locked of the satisfaction of fibre strain, magnet able to programme should have the magnetization magnetic hysteresis loop of rectangle, and its squareness ratio (remanent magnetization/saturated magnetization) is at least 0.85, was at least 0.90 better, was at least 0.95 better.In order to form required as shown in Figure 2 bar-shaped, wish especially with mechanically ductile and be easy to shaping or be easy to mach coupernick, for example Fe-Cr-Co, Cu-Ni-Fe, Co-Fe-V.Do not wish to use high-coercive force arranged (H for example _c＞permanent magnet 1000Oe), stable, for example Sm-Co or Nd-Fe-B (unless having changed over than low-coercivity) programme to remanent magnetization with the downfield of needs because be difficult to again.But these stable magnet can be used to provide basic (or biasing) field, combine with the field of magnet able to programme.

Next step installation step is to load onto at least one solenoid on the magnet component, applies a programming pulse or the field of short time then, to adjust or to remove the remanent magnetization in the magnet.This step rectification has become power and the strain on the fiber grating, thereby changes wavelength of optical signal or amplitude.Also can replace pulsed field with a constant DC field, but better with the DC pulsed field, to avoid providing constant electric current to solenoid.The time interval or speed that pulsed field needs are usually at 10-10 ^-8Second scope, 10-10 ^-6Second is better, and 10 ^-1-10 ^-4Second is better.To thick shape magnet, because eddy current loss is not wished with too fast pulse.The shape of current impulse can be the sinusoidal or the irregular shape of rectangle, rectification, as long as it is just passable to the required maximum field of predetermined surplus value to reach magnetization.

Final step is but that the grating of a plurality of magnetic tuning and breech locked and circulator and other opticses are assembled, and finishes this wavelength selective light cross connect system.

Example 1

A tunable fiber grating device is assembled according to following method.The no strain bragg reflection wavelength of this grating is 1549.7nm.Make the alloy bar (0.108 inch diameter) of Fe-28wt%Cr-7wt%Co, after wearing out through deformation, present H _c～85Oe and squareness ratio M _r/ M _sA magnetic hysteresis loop of (remanent magnetization/saturated magnetization)～0.97.Magnet length reduces to 2.2 inches, makes this M-H loop line inclination～30Oe.Fiber grating one end with epoxy resin bonding at magnet able to programme near space one end, and the other end of grating is bonded on the stainless-steel tube (internal diameter～O.150 inch), as shown in Figure 2, also will illustrate below.Another magnet able to programme (Fig. 2 left side magnet) next-door neighbour right side magnet is placed, with it every the air-gap of a 6mil, and with epoxy resin bonding on stainless-steel tube.This device is put in the solenoid, and allowed electric current pass through to remove electric current then, so that on fiber grating, generate remaining tensile strain to produce magnetic field.

Be drawn on Fig. 4 is to obtain wavelength-shift with this (6 channel shifter module) grating.Use 105,118,127,138 and the field of 168Oe respectively, the wavelength-shift that obtains is 0.8,1.6,2.4,3.2 and 4.0nm, and remains unchanged after removing the field.

For the operation of tunable and breech locked grating of the present invention, magnetize to certain tuning state, magnetize again to different tuning states, maybe to demagnetize to remove tensile strain fully, all must apply the magnetic field of suitable intensity.Desirable way is to reduce the magnetic field that solenoidal power (electric current) obtains certain intensity.

Many wavelength are selected the cross connection exchanger system, and the wavelength that requires grating to move may be smaller.For example, the Bragg grating of 2 * 2 interchangers of Fig. 1 (or N * N cross connection interchanger) at large, on the wavelength that the wavelength channel that can be parked in and require slightly departs from, for example, between two adjacent optical channels wavelength.To the application of these types, can be with as shown in Figure 5 bistable tunable optical gate device, what replace Fig. 2 type can be at the tuning adjustable grating of wideer wavelength coverage.

Fig. 5 exemplary bistable fiber bragg grating device 50 that schematically draws, it comprises that a long section contains the optical fiber 51 of refractive index perturbation grating 52.With bonding agent 53 or mechanical fixation, optical fiber firmly is fixed between magnet 54 capable of reversing and the guide housing 56, so that the magnetic force of magnet 54 is sent to grating 52 in the zone of grating.The magnet 55 not capable of reversing that is bonded on the cover 56 applies suction or repulsion to magnet 54 capable of reversing.Magnet 54 capable of reversing can be the guidepost shape, but the shape of noncircular cross section preferably, so that handling or reversing of optical fiber reduced to minimum during work.One or more electromagnet (solenoid) 57 next-door neighbour magnet 54 are placed so that enough magnetic field is provided, need the time make polarity reversing.Guide housing 56 is a pipe preferably, but also other shape can be arranged, for example, it can by U-shaped last slice and following sheet two parts assemble.

Guide housing 56 is made tubulose with glass, quartz, metal or plastics usually.Fiber grating or use mechanical fasteners, or with bonding, such as using epoxy resin, low-melting glass, or scolder make it attached on magnet 54 and the guide housing 56.As use scolder, optical fiber surface preferably applies the layer of metal layer, to improve the cohesive strength of scolder.Here with this bonding of bonding agent 53 expressions.Capable of reversing and movably magnet 54 and two immovable again magnet 55 not capable of reversing be in line, leave very little fixing (default) gap between them.These two orientations of magnet capable of reversing not, preferably mutually with same pole (S to S or N to N) relatively, magnet capable of reversing is placed between them.

During operation, capable of reversing and movably magnet 54 by the magnet not capable of reversing in the attraction not capable of reversing in left side and bump left side, by the attraction not capable of reversing on right side and clash into the magnet not capable of reversing on right side, with the magnetization polarity of the solenoid 57 of visual surround and decide.Because the arrangement of magnetic pole, magnet capable of reversing is when one of magnet capable of reversing repels, again by another attraction not capable of reversing.Because removable magnet has only two fixed positions, thus also have only the stationary state of two tensile strains, thus in the fiber grating that is fixed, also have only two grating wavelength states.Default gap between fixed magnet 55 and the removable magnet 54 has determined the mobile degree of grating wavelength in this bistable (numeral is tunable) device.A significant advantage of device shown in Figure 5, be the breech locked and the stability of the wavelength that is moved, apply a pulse or the electric current of short time as startup, afterwards to solenoid, removable magnet just is locked in one of two positions, no longer needs to continue to provide electric power.

Be sure of that fiber grating does not suffer twist distortion, this is crucial, because distortion has changed the dependent variable that is added on the grating, reduces the fracture strength of optical fiber under given tensile strain, and can make the light signal distortion.For eliminating or the minimizing twist distortion, will be for removable magnet be provided with guiding mechanism, under container section is circular situation, add guided way, or with the container of noncircular cross section and the magnet of a noncircular cross section, such as the container or the magnet of an ellipse or square-section.Optical fiber can be placed on outside the magnet, or is placed in the hole of magnet, or is placed in the groove of magnet.

Example 2

One bistable, tunable fiber bragg grating device are assembled into the structure of Fig. 5 according to following method.The bragg reflection wavelength of grating is 1556.480nm.Make the alloy bar (0.095 inch diameter) of Fe-28wt%Cr-7wt%Co, after wearing out through deformation, present H _c～93Oe and squareness ratio M _r/ M _sA magnetic hysteresis loop of (remanent magnetization/saturated magnetization)～0.97 is as the magnet removable, capable of reversing of Fig. 5.About 2 inches of magnet length.Magnet not capable of reversing (two 0.25 inch long, the Nd-Fe-B magnet of 0.125 inch diameter) is bonded in the two ends that the stainless steel guiding is closed.Fiber grating one end uses epoxy resin bonding at magnet left end capable of reversing, and the other end of grating is bonded on the stainless-steel tube, as shown in Figure 5.This device is put in the solenoid, and allow electric current pass through to remove electric current then, so that make the polarity reversing of remanent magnetization in the Fe-Cr-Co magnet capable of reversing to produce magnetic field, so it is not the Nd-Fe-B magnet in bump left side, be the Nd-Fe-B magnet in bump left side.

Fig. 6 is a curve map, is illustrated in the above-mentioned bistable grating device to apply ± the 200Oe field (carrying～1 millisecond of pulse current to solenoid), moves from the wavelength that experimentally obtains.When Fe-Cr-Co magnet bump left side (H=+200Oe), optic fiber grating wavelength is 1557.420nm, and (H=-200Oe) wavelength becomes 1556.480nm when magnet commutates, and clashes into the right side simultaneously.The wavelength of Δ λ=0.940nm moves usefulness ± 200Oe and commutates repeatedly, and it is repeatably that the wavelength of surperficial Δ λ=0.940nm moves.

Obtaining a selective embodiment of magnetic strain in optical fiber, is bending or the deflection that utilizes optical fiber, shown in Fig. 7 (a) and 7 (b).Shown in Fig. 7 (a), a long section contains the optical fiber 71 of grating 72, is fixed on the both sides of bearing support 76 with bonding agent 73.Make optical fiber produce the breech locked strain with a mechanical arm 74.Perhaps use the way of machinery, perhaps use the way of magnetic, fiber grating toward pressing down (or upwards drawing), preferably slightly leave the grating active region, so in grating, produce tensile strain, thereby change its resonance wavelength (for example bragg reflection wavelength in the Bragg type grating, or the peak coupled wavelength in long period type grating).More preferably, it is breech locked that the strain of generation and wavelength move, and for example utilizes certain mechanical spring bolt type structure, or shown in Fig. 7 (b), utilizes the attraction or the repulsive force of magnetic.Removable magnet 77 usefulness spring arms 78 link to each other with bearing support, and it is partly discharged by magnetic attraction, or discharge fully, by the magnetization size decision of magnet 79 able to programme.

According to bistable tunable devices of the present invention some advantages are arranged.The wavelength that it produces moves, and is breech locked after remove the field that applies, and need not to continue consumed power and keeps moving of wavelength.The structure of device is simple relatively, and it is not crucial that switching puts on solenoidal electric current (or voltage) when starting because the electric current that applies (or voltage) need only " greater than " a certain minimal value, make switch over operation work.The speed that wavelength moves (or the channel branch/insert) can be fast relatively, for example fast than 10 milliseconds.

Grating described herein is particularly useful in the wavelength division multiplexing communications that adopts multiplexer/demultiplexer is identical.In this type systematic, one " main line " optical fiber carries some wavelength X ₁, λ ₂... λ _nOptical signal channels, it need tell the channel of certain single wavelength from fiber optic backbone, or the channel of certain single wavelength is inserted main line.All this class devices can both be made of interconnection optical circulator and fiber grating.Usually be to tell or insert main line by the channel of optical grating reflection from trunk fiber.Grating described herein can select tell or insert which channel on grating.Can place a series of bistable adjustable gratings between a pair of circulator, their grating wavelength fixes on the wavelength of interchannel.The grating that startup needs is made half channel wavelength and is moved, and the adjacent communication channel is told or inserted.

Turn around with reference to figure 1, but magnetic control fiber grating 105 place along the interconnection fabric 125-128 between optical router part 150 and the optical combiner part 151, be beneficial on the basis of wavelength one by one, finish signaling transfer point.More specifically say, the route of each channel of multiple wavelength optical signal, be along interconnection fabric 125-128, be in transmissive state (be certain specific wavelength channel will through optical fiber) or be in reflective condition (being that certain specific wavelength channel will be gone back by fiber reflection) according to fiber grating 105 and control.

III. some embodiment of this selective interchanger

Fig. 8 (a) is according to the principle of the invention, embodiment 2 * 2 optical exchangers 200 that draw and changed.Be similar to the embodiment of Fig. 1, optical exchanger 200 comprises an optical router part 270 and an optical combiner part 271.The optical router part 270 that comprises photo-

coupler

201 and 202 is to multi-wavelength light input signal I ₁And I ₂Distribute.Comprise the optical combiner part 271 of photo-

coupler

203 and 204, multiple wavelength optical signal is combined, as output signal O ₁And O ₂And export.Say that more specifically photo-

coupler

201 and 202 receives multi-wavelength light input signal I respectively ₁And I ₂, and photo-

coupler

203 and 204 is sent multi-wavelength light output signal O respectively ₁And O ₂Photo-coupler 201-204 can comprise passive photo-coupler, the star-type coupler of for example knowing in the industry, or any other known device that can the coupling light energy.For ease of explanation, explanation after this all refers to star-type coupler 201-204.

Star-type coupler 201-204 is coupled through interconnection fabric 205-208, and optical fiber 205-208 is equipped with wavelength within it to select the wavelength of element 210 to select optical fiber.Wavelength selects element 210 to be made of the tunable fiber Bragg grating of knowing in the industry, or any other known wavelength selective filters.For ease of explanation, explanation after this all refers to fiber grating 210.As shown in the figure, optical fiber 205 comprises fiber grating 210A, and optical fiber 206 comprises fiber grating 210B, and optical fiber 207 comprises that fiber grating 210C and optical fiber 208 comprise fiber grating 210D.As shown in the figure, star-type coupler 201 is selected optical fiber 205 through wavelength, along through path and star-type coupler 203 couplings.Star-type coupler 201 is selected optical fiber 206 through wavelength, along bridged path and star-type coupler 204 couplings.Equally, star-type coupler 202 is selected optical fiber 208 through wavelength, along through path and star-type coupler 204 couplings.Star-type coupler 202 is also selected optical fiber 207 through wavelength, along bridged path and star-type coupler 203 couplings.

Shown in Fig. 8 (a), option optoisolator 220 also can be coupled with the input port and the delivery outlet of each star-type coupler, so that intercept the backward scattering or the reflection of the light signal that may damage some parts, shields.Therefore, option optoisolator 220 can be used for reducing the interference that produces from unwanted reflection (as the opposite direction transmitting signal).

Star-type coupler 201 and 202 can be 1 * 2 coupling mechanism, and it is broadcast to all outputs to a light signal as input.Star-type coupler 203 and 204 is 2 * 1 coupling mechanisms, and its single output is made up all inputs and constituted.The principle of work of star-type coupler is well-known.For example well-known, 1 * M photo-coupler is its single input, such as a multiple wavelength optical signal, is broadcast in its M the delivery outlet each fifty-fifty.Though Fig. 8 (a) illustrated embodiment should point out that with 1 * 2 and 2 * 1 star-type couplers the principle of the invention can be used in combination with the star-type coupler of any size.Therefore, the embodiment that shows here and illustrate is exemplary, can not be interpreted as restriction.For example, the back also will be described in more detail, utilize basic two-stage cross-connect structure, according to the principle of the invention, can realize the cross-connect of any size, wherein optical router part 270 is represented one-level (being used for route signal), and optical combiner part 271 is represented another level (being used for composite signal).Therefore, and compare with the existing apparatus of multistage interchanger mechanism, this structure is simpler and more cheap.

With reference to figure 8 (a), star-type coupler 201 each delivery outlet will carry whole multiple wavelength optical signal I again ₁(be all wavelengths, from λ ₁To λ _n) the part of luminous energy, and star-type coupler 202 each delivery outlet will carry whole multiple wavelength optical signal I ₂(be all wavelengths, from λ ₁To λ _n) the part of luminous energy.Multi-wavelength light input signal I ₁Thereby by star-type coupler 201, be broadcast to wavelength and select

optical fiber

205 and 206 on both.And input signal I ₂Then by star-type coupler 202, be broadcast to wavelength and select

optical fiber

207 and 208 on both.

Because whole wavelength signals is broadcast to all outputs of corresponding star-type coupler, so the wavelength of all interconnection star-type coupler 201-204 is selected all will place fiber grating 210 on the optical fiber.Each path all needs fiber grating 210, so selecteed specific wavelength channel can suitably see through or reflection in the interconnection fabric 205-208 between star-type coupler 201-204.In specific embodiment shown in Fig. 8 (a), fiber grating 210 can be used as bandpass filter and works, tuning it, allow from multiple wavelength optical signal I ₁And I ₂The specific wavelength channel of selecting is passed through.For example, can tunable fiber grating 210A, only allow the wavelength of selecting pass through, arrive star-type couplers 203 from star-type coupler 201.Equally, can tunable fiber grating 210B, allow other wavelength of selecting pass through, arrive star-type couplers 204 from star-type coupler 201.Fiber grating 210C and 210D also can be tuning similarly, allow the wavelength of selecting on demand pass through.

During operation, optical exchanger 200 is different from optical exchanger 100 (Fig. 1), and difference is that the purposes of star-type coupler is opposite with optical circulator.Say that more specifically multiple wavelength optical signal is made up of each channel, each channel has its specific wavelength, and multiple wavelength optical signal is as input I ₁, be transferred into the star-type coupler 201 in the optical router part 270.Star-type coupler 201 (is whole multiple wavelength optical signal a wavelength X ₁To λ _nWhole channels) broadcast or route to wavelength and select optical fiber 205 and 206.Those have each channel that fiber grating 210A sees through the wavelength of band, connect as " leading directly to ", are transferred into star-type coupler 203.This " leading directly to " route is equivalent to the horizontal state of crossbar switch on function.Each wavelength channel that those have the wavelength of the fiber grating 210A zone of reflections is reflected back toward star-type coupler 201.Similarly, those have each channel that fiber grating 210B sees through the wavelength of band, select optical fiber 206 through wavelength, are transferred into star-type coupler 204.Cross connection route between star-type coupler 201 and 204 is equivalent to the vertical state of crossbar switch on function.Each channel that those have fiber grating 210B zone of reflections wavelength is reflected back toward star-type coupler 201.Identical principle of work is applied to enter the light signal I of star-type coupler 202 ₂, be simple meter, no longer repeat here.

In optical combiner part 271, star-type coupler 203 receives each channel of specific wavelengths, these specific wavelength channel from star-type coupler 201 along optical fiber 205 in " lead directly to " path route.Star-type coupler 203 also receives each channel of specific wavelength, and these specific wavelength channel 207 are come in " cross connection " path route from star-type coupler 202 along optical fiber.203 each channels from the different wave length of its all input end of star-type coupler combine, and a multiple wavelength optical signal of combination is as output O ₁Send.Identical principle of work is applied to star-type coupler 204, is simple meter, no longer repeats here.In fact, output signal O ₁Both can comprise from input signal I ₁Each channel (" leading directly to " channel), also can comprise from input signal I ₂Each channel (" cross connection " channel).

Fig. 8 (b) the draw sketch of a specific example of optical exchanger 200 operation, wherein multiple wavelength optical signal I ₁Comprise that (wavelength is λ to two independent channels ₁And λ ₂), and multiple wavelength optical signal I ₂Comprise that (wavelength is λ to two independent channels ₃And λ ₄).As figure, be assumed to the cross connection situation, wherein need output signal O ₁Comprise wavelength channel ₁And λ ₃, and output signal O ₂Comprise λ ₂And λ ₄Therefore, optical exchanger 200 (Fig. 8 (b)) will be configured to, and fiber grating 210A sees through wavelength X ₁And reflected wavelength lambda ₂Fiber grating 210B sees through wavelength X ₂And reflected wavelength lambda ₁Similarly, fiber grating 210C sees through wavelength X ₃And reflected wavelength lambda ₄, fiber grating 210D sees through wavelength X ₄And reflected wavelength lambda ₃Should be pointed out that this example shows, in different input and output signals (as I ₁, I ₂, O ₁, and O ₂) wavelength of each channel assigns, there is no need identical, though be simplified illustration, each all with Expression.

Consider the narration of front, can see that fiber grating 210A-210D is used in combination with optical router part 270, help in multiple wavelength optical signal, route (as broadcasting, distribute, or the like) each wavelength channel.Same fiber grating 210A-210D is used in combination with optical combiner part 271, helps in multiple wavelength optical signal, combination (as along separate routes, be coupled, or the like) each wavelength channel.Selecting in the optical fiber 205-208 with each wavelength of star-type coupler 201-204 interconnection, by adding tunable fiber grating 210, optical exchanger 200 obtains wavelength selection cross connection capability very flexibly thus.

According to another aspect of the present invention, Fig. 8 (a) shows, utilizes star-type coupler 201-204 to go up in the past no mouthful, can obtain wavelength and select this machine branch/slotting performance.As figure, former no input port 250 can be used on star-

type coupler

201 and 202, so that the separate channel of specific wavelength, inserts in the multiple wavelength optical signal.Equally, former no delivery outlet 260 can be used on star-

type coupler

203 and 204, so that the separate channel of the specific wavelength of selecting, tell from multiple wavelength optical signal.

During operation,, utilize the function of telling of star-type coupler, may require the parts that add, select element, the wavelength channel that tell is leached as wave filter or other wavelength according to Fig. 8 (a) embodiment.For example, on minute outbound path 260, need one only to see through λ ₁Wavelength selective filters so that from multiple wavelength optical signal, only tell wavelength channel ₁Being also pointed out that branch/inserting structure of Fig. 8 (a), only is exemplary.So astute in the industry personage should be understood that any combination of available mouth on star-type coupler 201-204, all can be as required as inserting or the branch outbound path.Only for giving an example, star-

type coupler

201 and 202 also can support to tell function, and this depends on available mouth.

Utilize the advantage of the wavelength selective power of the dirigibility of star-type coupler design and fiber grating, need not to change the elementary heat exchanger structure, just can enlarge programmable branch/slotting ability.Particularly, divide/insert expansion property of ability to be that star-type coupler can design additional mouth, in order to using in the future, programmability then is, fiber grating energy foundation will be told the wavelength channel that is selected that maybe will insert and tuning or programme.

Fig. 9 K * M optical cross connection device 300 that draws.Except pointing out below, the principle of work of front explanation 2 * 2 optical exchangers 200 (Fig. 9 A), the K that can be used for illustrating here equally * M optical cross connection device 300.

In brief, optical cross connection device 300 receives K multiple wavelength optical signal as input, wherein each light signal has each channel of different wave length, then each channel of multiple wavelength optical signal, route between input of K cross-connect and M cross-connect are exported, and send M multiple wavelength optical signal as output.Optical cross connection device 300 comprises an optical router part 340 and an optical combiner part 341.The optical router part 340 that comprises photo-coupler 310, broadcasting be the 305 multiple wavelength optical signal I that receive from K cross-connect input port ₁, I ₂, to I _KComprise the optical combiner part 341 of photo-coupler 320, multiple wavelength optical signal combined, and they as output O ₁, O ₂, to O _M, deliver at M cross-connect delivery outlet 315.Fiber grating 330 is provided with along interconnection fabric 325, in order to each channel of route multiple wavelength optical signal between optical router part 340 and optical combiner part 341.

Be simplified illustration, input I only draws among Fig. 9 ₁, I ₂, and I _KAnd output O ₁, O ₂, and O _M, and omit I ₃To I _K-1And O ₃To O _M-1In addition, for the purpose of simplifying the description, each input and output all is drawn as and comprises one group of identical wavelength, with

Expression, but change the different wavelength of respectively organizing easily into.

K cross-connect input port 305 is coupled with input optical fibre 301 to 303, to receive multi-wavelength input optical signal I ₁, I ₂, to I _KOne input photo-coupler 310, links in router section 340 and each cross-connect input port 305 as 1 * M star-type coupler that an input port and M delivery outlet are arranged at this.Each imports photo-coupler 310, can be broadcast to multiple wavelength optical signal from its single input port its M delivery outlet.In the optical combiner part 341 of optical cross connection device 300, a plurality of cross connection delivery outlets 315 and the output optical fibre 350-352 coupling of carrying the multiple wavelength optical signal that is routed.One output optical coupler 320, at this as K * 1 star-type coupler of K input port and single delivery outlet is arranged, with each cross connection delivery outlet 315 to connection.Each output optical coupler 320 can combine each wavelength channel that its all input ports receive.

Input photo-coupler 310 and output optical coupler 320 are selected optical fiber 325 by the interconnection wavelength, are coupled.Wavelength selects optical fiber 325 to comprise that wavelength selects element 330, such as tunable fiber grating, according to aforementioned other embodiment same way as, see through or the reflection multiple wavelength optical signal in any of each wavelength channel.The wavelength of interconnection is selected optical fiber 325, and a kind of exchanger arrangement that connects fully is provided, and it can be on choke free basis, arbitrary multi-wavelength light input signal I ₁, I ₂, to I _KArbitrary N wavelength channel, route to arbitrary cross connection delivery outlet 315.

By the previous embodiment same way as, fiber grating 330 is in conjunction with optical router part 340, is used to improve the route (as broadcasting, distribute, or the like) of each wavelength channel in the multiple wavelength optical signal.Identical fiber grating 330 is in conjunction with optical combiner 341, also is used to improve the combination (as multiplexing, coupling, or the like) of each wavelength channel in the multiple wavelength optical signal.Select in optical fiber 325 at each wavelength of interconnect photo-coupler 310 and 320, by adding tunable fiber grating 330, therefore optical cross connection device 300 obtains the ability of wavelength selection cross connection very flexibly.

As shown in Figure 9, K * M exchanger arrangement has KM root wavelength to select optical fiber 325, and optical router part 340 and optical combiner part 341 are interconnected, and K represents the number of cross connection input port 305 here, and M represents the number of cross connection delivery outlet 315.Work as K=M, Fig. 9 equal number input port and delivery outlet symmetry interchanger that drawn.Therefore,, between each input photo-coupler 310 and each output optical coupler 320, there are 3 wavelength to select optical fiber, always have 9 wavelength and select optical fiber be configured to 3 * 3 cross-connects on basis with Fig. 9.But, should be pointed out that the cross connection device of any size, no matter be the square interchanger matrix of K=M, or the non-square interchanger matrix of K ≠ M, can be used for realizing the present invention.Importantly, embodiment illustrated in fig. 9 showing, how according to the principle of the invention, with basic two-stage cross connecting structure, realize the cross-connect of any size, wherein optical router part 340 is represented one-level (being used for receiving and route K multi-wavelength light input signal), and optical combiner part 341 is represented another level (be used for combination and send M multi-wavelength light output signal).As noted, this cross connecting structure is than the existing apparatus that comes the route signal with multistage exchanger arrangement, more cheap and more simple.

The number of tunable fiber grating 330 also can be according to the size of cross connection device and special fiber grating planned use and is changed.For example, one independently tunable fiber grating 330 can be used for each of N wavelength, perhaps single tunable fiber grating 330 can be used for seeing through or N wavelength of reflection in more than one wavelength.Also have, wavelength selects optical fiber 325 can comprise other fiber gratings of other purposes, flattens as gain.For example, at once, for the switching of each channel in the multiple wavelength optical signal of carrying out N wavelength channel, the number of fiber grating 330 is KMN 330 of each tunable fiber gratings and N wavelength channel one.For example, with 4 wavelength systems of 3 * 3 cross-connects, promptly K=M=3 and N=4 between each input photo-coupler 310 and each output optical coupler 320, have 3 wavelength to select optical fiber 325, always have 9 wavelength and select optical fiber.Because 4 wavelength each must be reflected/see through in each path, but 36 magnetic tuning fiber gratings to be arranged.Say again, under without departing from the spirit and scope of the present invention, the foregoing description can also have other variation or change.

If big cross connection exchanger arrangement, promptly big KM when signal is broadcasted and made up by photo-coupler, may need to amplify with compensation and insert and other losses.There are many different amplifier patterns to adopt in conjunction with argumentation of the present invention.For example, can be with various semiconductor optical amplifiers and optical amplifier fiber.Fiber amplifier, particularly Erbium-Doped Fiber Amplifier (EDFA), the insider knows, and uses in the example that will set forth below.Should be pointed out that though Erbium-Doped Fiber Amplifier (EDFA) is particularly suitable for being used in the present invention amplifying, and will set forth at this, also can be with other suitable rare earth element elements, as praseodymium, neodymium and so on.

According to the principle of the invention, optical fiber amplifies and can insert with many different allocation plans.For example, can be placed on the fiber amplifier (not shown) before the input photo-coupler 310 of optical router part 340, or after the output optical coupler 320 of optical combiner part 341.Perhaps, can select the fiber amplifier (not shown) to distribute in the optical fiber 325 in compensation, its mode duplicates described in our patent that awaits the reply, the US application serial No. No.08/777 of this patent, 890,12/31/96 registrations, this monopoly gain here, for your guidance.Also has another kind of allocation plan, can select the optical amplifier fiber (not shown) optical fiber 325 integrated with tunable fiber grating 330 along wavelength, as described in our patent that awaits the reply, the US application serial No. No.08/920 of patent, 390 and 08/920,391, all in 8/29/97 registration, the both takes in here, for your guidance.

Though obviously be not drawn on Fig. 8 and 9, can consider, can control each fiber grating that in fiber grating 210 and 330, is selected respectively, with suitable " leading directly to " route and " cross connection " route of improving each channel in the multiple wavelength optical signal.Therefore, the various control technologys that prior figures 1 is described can be used for Fig. 8 and 9 illustrated embodiments equally.

Figure 10 (a) input photo-coupler 310 of optical router part 340 in the optical cross connection device 300 (Fig. 9) that draws.The structure of Figure 10 (a) is one 1 * M wavelength selective light divider basically, and it is that K * M wavelength is selected the basic standardized component of cross connection device.As previously mentioned, each input photo-coupler 310 constitutes as passive star coupler usually by one 1 * M photo-coupler, and wherein single input signal is broadcasting between M output.In fact, one 1 * M photo-coupler as 1 * M star-type coupler, normally is fused together making to M photo-coupler, so M input and M output are arranged.In fact, one 1 * M photo-coupler is one M * M photo-coupler basically.Since it is so, one 1 * M photo-coupler will have identical loss and cost of manufacture with one M * M coupling mechanism.But when using, only an input with 1 * M coupling mechanism receives an input signal, is broadcast to M output then.

On the basis of this example, how Figure 10 (a) utilizes photo-coupler 310 in the past no mouths that additional function is provided if drawing.Except that receiving the cross connection input port 305 of multiple wavelength optical signal by input optical fibre 301, former no input port 401 can be used for transmitting the pump light of pumping source (not shown) to the optical amplifier fiber (not shown).Equally, no input port 402 before another can be used for this machine transplanting of rice inlet, and wavelength channel is inserted in the multiple wavelength optical signal.Except that being used to broadcast the delivery outlet of multiple wavelength optical signal by wavelength selection optical fiber 325, former no delivery outlet also can be made this machine and divide outlet 403, tells each wavelength channel, or as visit mouth 404, the execution monitoring function, and so on.The option isolator 420 that also draws in these are used, as described above, it is used to intercept retroeflection, shields.

Equally, Figure 10 (b) output optical coupler 320 of optical combiner part 341 in the optical cross connection device 300 (Fig. 9) that draws.This structure of Figure 10 (b) is a K * 1 wavelength selective light combiner basically, and it is another kind of K * basic standardized component of M cross connection device.As previously mentioned, each output optical coupler 320 constitutes as passive star coupler usually by a K * 1 photo-coupler, wherein K input signal is combined into single output.As shown, former no input and output mouth on the output optical coupler 320 can be used to provide additional function by the same way as of front to 310 explanations of Figure 10 (a) input photo-coupler.For example, photo-coupler 320 can comprise that machine transplanting of rice inlet 405, this machine divide mouthful 407 and one mouth 408 that monitors that exports 406, is used for pump light.

Wavelength selective light cross connection device according to the principle of the invention, can support the multi-wavelength system (being the input and output of wavelength and any number of any number) of any size, and can hold additional business need, need not again exchanger arrangement is done great change, in this sense, it has very big design flexibility.As previously mentioned, this cross connection device is also supported the expansion of branch/slotting capacity, and the capacity of expansion can the dynamically increase and decrease by branch/slotting requirement.This cross connection device is being told and is being continued on application aspect two and the broadcasted application also of great use.

IV. the encapsulation of interchanger

Know that when variation of ambient temperature, the performance of fiber grating will change.For example see the U.S. Patent No. 5,694,503 that on Dec 2nd, 1997 was presented to people such as D.A.Fleming.In Bragg grating, n _EffDepending on temperature with the ∧ both, is example with the silica-based optical fiber, its pure relation that depends on temperature, on λ=1550nm pact+0.0115nm/ ℃.The reflection wavelength that temperature produces moves usually mainly due to n _EffChange with temperature.Thermal expansion produces the variation of ∧, only is the pure sub-fraction that depends on the relation of temperature of silica based grating.Be reliability and the repeatability of assurance wavelength selective light cross connect system in optical-fiber network, possible performance change, the performance change that causes as variation of ambient temperature should reduce to minimum or elimination.In the present invention, the embodiment that income is additional, its cross connect system are irrelevant with variation of ambient temperature basically.Below three kinds of methods all be used for this purpose.

1) guarantee the device system package method that its environment temperature is constant---for this reason, shown in Figure 11 (a), but all magnetic control gratings all suitably be encapsulated in the single constant temperature oven 130, on the temperature that is operated in fixing 40 degree C.Perhaps shown in Figure 11 (b), can put the overall optical cross connect system into stove 130.Otherwise all gratings or cross connect system encapsulate with a thermoelectric cooling module (sees the L.A.Johnson paper, Laser and Optoelectonics, April, 1998, p.109 and the J.R.Hobbs paper, Laser Focus World, February, 1993, p.117) contact and be placed on the thermoelectric cooling module vicinity, make any temperature, C is maintained as zero degree.Temperature Feedback and relevant thermoregulator mechanism can suitably be quoted.

2) when changing, the device system package method can provide feedback when magnetic tuning grating wavelength state is influenced by ambient temperature, and automatically wavelength is corrected to allowing optical channel pass through or the right value of elimination.Can use spectroanalysis instrument, or spectrum tap device, combine with the signal feedback system that starts magnetic-pulse in the suitable grating solenoid, also combine with optional temperature sensor.The added advantage of this feedback system is, it moves all unwanted wavelength, causes as mechanical vibration, and the creep of encapsulation adhesives such as epoxy resin causes, and depends on the wavelength that the relation of temperature causes and move, and correction is provided without exception.

3) but the device package method of automatically (passive) temperature compensation is provided in the magnetic tuning optical grating construction.Because the grating temperature rising can cause the increase of bragg wavelengths, mainly be because at n _EffIn depend on the increase of the relation of temperature, compensate this effect so must reduce grating cycle ∧, make λ temperature independent.Accomplish this point, when for example beginning optical fiber is applied prestress,, or be in the magnetic strain tuning state, then, when environment temperature increases, make tension force release (or when temperature reduces, making the tension force grow) with it basically in the grating with being directly proportional such as tension force.To the silica-based optical fiber grating of typical germnium doped core, be the blunt bragg wavelength of holding temperature, the thermal shrinkage range of strain that requires when being heated, the temperature variation of general per 100 ℃ of C is 900 * 10 ^-6, in other words, effectively CTE is about-9 * 10 ^-6/ ℃.

The present invention gives adjustable grating (continuous with structure bistable) with passive temperature compensation ability, based on four class mechanism: (ⅰ) via one or more parts, fiber grating is sticked on the removable magnet, these parts are by the special screening of CTE, can reduce tensile strain in the fiber grating, and compensation temperature causes the increase of grating resonance wavelength, (ⅱ) utilize temperature to cause the increase of magnetic gap between the pairing magnetic pole, the for example thermal expansion by bearing support, because one of magnet assembly sticks on the bearing support, thereby reduce relevant magnetic force, reduce elastically-deformable degree in the fiber grating thus, (ⅲ) adopt the element that at least one has elongated, fiber grating is bonded on the guide pipe, as an expander and a strain relief, utilize its thermal expansion to reduce thermal strain on the bonded grating, (ⅳ) utilize temperature to cause the loss of the intensity of magnet magnetic able to programme, not to utilize the intrinsic heat scattering loss, utilize the expansion gap material of introducing to increase the leakage of flux exactly, reduce magnetic flux at magnetic pole gap, thereby reduce magnetic attraction, thereby reduce the tensile strain that magnetic causes in the grating.Should be pointed out that to continuously adjustable and two kinds of situations of bistable there is subtle difference in the mode that obtains temperature compensation, the former depends on the intensity by control gap or magnetic more, changes magnetic attraction, and the latter directly depends on the strain that discharges in the optical fiber.

As an example, a kind of passive temperature compensation package method that is used for bistable optical grating construction (but magnetic switching between two fixed grating wavelength) schematically is drawn on Figure 12 (a).On the figure, insert a negative CTE element 20, and it is bonded at that optical fiber is inducted and removable magnet 24 (its magnetization is able to programme and breech locked) between.The temperature compensation packaging system must comprise certain structure or certain structure member, will shrink when its length is heated, and in other words, having is the thermal expansivity of bearing (CTE) substantially.Thereby, the material of the negative CTE value of this class or the structure that is assembled into are arranged, be desirable as the temperature compensating element of tunable wave length fiber grating.Desirable negative CTE example of material comprises: stupalith such as ZrP ₂O ₇, ZrV _2-xPO, and ZrW ₂O ₈(see C.Martinet etc., J.Am.Ceram.Soc., Vol.51, p.227,1968, T.A.Mary etc., Science, Vol.272, p.9,1996 and V.Korthuis etc., Chem.of Materials, Vol.7, p.412,1995 papers such as grade) these papers have also been described the negative CTE material of metal, as Ni-Ti alloy (48-64 wt%Ni), Cu-Al-Zn alloy (1-10%Al, 20-40%Zn, balanced Cu), Cu-Al-Ni alloy (10-20%Al, 1-5%Ni, balanced Cu), Cu-Zn-Si alloy (30-40%Zn, 0.5-1.5%Si, balanced Cu) and Cu-Sn alloy (20-30%Sn, balanced Cu) (sees U.S. Patent application, sequence number 08/957,953, D.A.Fleming was in registration in October 27 in 1997).Can control the chemical property and the disposal route of metal, pottery or compound substance, obtain the negative CTE value that needs.

The effect temperature compensation of Figure 12 (a) device obtains as follows.As Figure 12 (b), when removable magnet was converted to right positions facing to right side magnet 25, temperature effect was determined that by two principal elements promptly temperature causes that the wavelength of grating increases and bear the thermal shrinkage of CTE element.The small distance (sub-fraction that comprises removable magnet between two right side bonding points, the length of the length of one section weak point of permanent magnet and 29 1 sections weak points of bearing) thermal expansion also there is contribution, but its effect is little, and can be by regulating the length or the CTE value of good fortune CTE element, and it is suitable to make it simply.By mating negative CTE, approximately be-9ppm/ ℃ just to obtain passive effect temperature compensation to desired value.

If Figure 12 (a) device is converted to the higher wavelength state that is shown in Figure 12 (a) now, removable magnet is adsorbed on the permanent magnet of left side by magnetic force.Under this state, magnet able to programme and bearing support, both thermal expansions all have contribution to temperature effect, and influence stretches so that and grating wavelength.The present invention advises using the magnet 24 able to programme and the CTE of bearing support 26 to mate (adapting to other widgets, length difference or the like with less transferring), because in this case, the magnet of placing able to programme and the thermal expansion of bearing support have been cancelled Z-shapedly.Replace single negative CTE element, comprise three kinds of negative CTE set composites positive or zero CTE material, be placed in the Z-shaped structure of a compactness, can replace the negative CTE element of Figure 12.Effective thermal shrinkage when being heated, the 3rd straight rod that can utilize the straight rod of two different CTE to bond abreast gone up and obtained.

Should be understood that above-mentioned each certain embodiments only is used for illustrating the principle of the invention, skilled person can be made various variations not departing under spirit of the present invention and the covering scope in the industry.For example, notice several suitable material systems, can be used for each embodiment of front, comprising, but be not limited to lithium niobate, and silicon light stool, the semiconductor system, like that.Because these examples are to be illustrative rather than definitive thereof, the various variations of embodiment can be planned to come from explanation of the present invention.Therefore, covering scope of the present invention only is subjected to the restriction of following claims.

Claims

1. controlled, selectable optical cross connect interchanger of wavelength, comprise that a plurality of input ports are to receive multiple wavelength optical signal, with a plurality of delivery outlets to send multiple wavelength optical signal as optical exchanger output, each multiple wavelength optical signal comprises a plurality of channels again, one of them channel is relevant with a specific wavelength, and this optical exchanger also comprises:

An optical router part is with the coupling of a plurality of input ports, to distribute the multiple wavelength optical signal from the input port;

An optical combiner part is with a plurality of delivery outlet couplings, with the combination multiple wavelength optical signal; With

Multifiber, interconnection optical router part and optical combiner part, but some optical fiber of selecting from multifiber contain the fiber grating that wavelength is selected magnetic tuning, it can allow in a plurality of channels any channel by or reflection, so can deliver to any channel in a plurality of channels from any input port of a plurality of input ports any delivery outlet of a plurality of delivery outlets.

2. according to the optical cross connect interchanger of claim 1, wavelength wherein selects element to comprise Fiber Bragg Grating FBG, changes but its wavelength is a magnetic.

3. according to the interchanger of claim 1, tuning magnetic interaction with adjacent pole is wherein finished.

4. according to the interchanger of claim 1, wavelength wherein can pin after being chosen in excitation, need not to continue to provide power to keep selected wavelength.

5. according to the interchanger of claim 2, wavelength is wherein selected, and is the magnetic pumping with the magnetic field intensity of needs, selects a wavelength that needs and finish from the continuous spectrum of wavelength.

6. according to the interchanger of claim 1, wavelength is wherein selected, and selects a wavelength that needs the available wavelength and finish on numeral, and available wavelength is in the design of optical fiber grating structure with predefined in assembling on the numeral.

7. according to the interchanger of claim 1, wherein optical router partly comprises a plurality of input photo-couplers, each input photo-coupler is relevant with one of corresponding a plurality of input ports, wherein optical combiner partly comprises a plurality of output optical couplers, and each output optical coupler is relevant with one of corresponding a plurality of delivery outlets.

8. according to the interchanger of claim 7, wherein a plurality of input photo-couplers and a plurality of output optical coupler comprise star-type coupler.

9. according to the interchanger of claim 8, each of wherein a plurality of input photo-couplers is one 1 * M photo-coupler, and each of a plurality of output optical couplers is a K * 1 photo-coupler, here K is an integer that equals the input port number, M is an integer that equals the delivery outlet number, and wherein each multiple wavelength optical signal comprises N channel, simultaneously, the multiple wavelength optical signal that N channel arranged, route between K input port in one K * M cross connection mechanism and M the delivery outlet.

10. according to the interchanger of claim 9, K=M wherein.

11. according to the interchanger of claim 1, also comprise a controller, it controls tunable fiber grating selectively according to command signal, with reflection or by any channel in a plurality of channels.

12. according to the interchanger of claim 11, but fiber grating wherein is the magnetic tuning fiber grating, and controller wherein is by applying magnetic field, selectively to fiber grating tuning.

13. according to the interchanger of claim 11, controller wherein selectively one that see through and one the reflection duty between the interchanger fiber grating.

14. according to the interchanger of claim 11, wherein selecteed each fiber grating is controlled as one group.

15. according to the interchanger of claim 11, wherein each fiber grating is independent controlled.

16. according to the interchanger of claim 1, optical cross connect interchanger wherein is to be contained in the temperature compensation encapsulation, makes the performance of interchanger and environment temperature irrelevant.

17.,, be to obtain wherein by at least one constant temperature oven that holds optical cross-connect is set with the irrelevant character of environment temperature according to the interchanger of claim 16.

18. according to the interchanger of claim 16, wherein with the irrelevant character of environment temperature, at least one thermoelectric cooling module obtains by being provided with near optical cross-connect.

19. according to the interchanger of claim 16, wherein with the irrelevant character of environment temperature, be by providing a wavelength to detect and feedback system, also the tunable fiber grating wavelength obtains by adjusting on one's own initiative with the magnetic-pulse excitation again.

20. according to the interchanger of claim 7, wherein a plurality of input photo-couplers and a plurality of output optical coupler, no mouth before each all comprises, these mouthfuls can insert in the multiple wavelength optical signal selectively each specific wavelength channel.

21. according to the interchanger of claim 7, wherein a plurality of input photo-couplers and a plurality of output optical coupler, no mouth before each all comprises, these mouthfuls can be told from multiple wavelength optical signal selectively each specific wavelength channel.

22. according to the interchanger of claim 7, also comprise the fiber amplifier of a doped rare earth element that is coupled with a plurality of input photo-couplers, the multiple wavelength optical signal a reception of a plurality of input photo-coupler correspondences carries out light amplification.

23. according to the interchanger of claim 7, also comprise the fiber amplifier of a plurality of doped rare earth elements that are coupled respectively with a plurality of output optical couplers, a multiple wavelength optical signal of sending a plurality of output optical coupler correspondences carries out light amplification.

24. interchanger according to claim 7, the fiber amplifier that also comprises a plurality of doped rare earth elements, within each the root optical fiber that has wavelength to select to be selected in the multifiber of element, be coupled, the fiber amplifier of each doped rare earth element, multiple wavelength optical signal between a plurality of input photo-couplers and a plurality of output optical coupler carries out light amplification.

25. an optical cross-connect comprises:

At least two input directional lights transmit device, and each can both receive multiple wavelength optical signal, and each multiple wavelength optical signal comprises a plurality of channels, and one of them channels associated a certain wavelengths;

At least two input directional lights transmit device, and each can both send multiple wavelength optical signal, as the output of optical cross-connect; With

At least two input directional lights are transmitted device to multifiber and at least two output directional light transmit device interconnection, each root optical fiber of from multifiber, selecting, comprise that but at least one has the magnetic control wavelength to select element, it can by or reflect any channel in a plurality of channels, so any channel in a plurality of channels, any that can transmit devices from these at least two input directional lights routes to any that these at least two output directional light transmit devices.

26. according to the cross-connect of claim 25, but but wavelength wherein selects element to comprise the fiber grating of magnetic tuning and magnetic latch.

27. according to the cross-connect of claim 25, at least two input directional lights wherein transmit device and at least two output directional light transmit device, each all comprises an optical circulator.

28. according to the cross-connect of claim 25, at least two input directional lights wherein transmit device and at least two output directional light transmit device, each all comprises a photo-coupler.

29. according to the cross-connect of claim 26, also comprise a controller, it is according to command signal, but control magnetic tuning fiber grating selectively, with reflection or by any channel in a plurality of channels.

30. according to the cross-connect of claim 29, fiber grating wherein is a tunable fiber grating, and controller wherein is by applying pulsed magnetic field, selectively to fiber grating tuning.

31. according to the cross-connect of claim 29, controller wherein selectively one that see through and one the reflection duty between the interchanger fiber grating.

32. according to the cross-connect of claim 29, wherein selecteed each fiber grating is to control as one in linkage group.

33. according to the cross-connect of claim 29, wherein each fiber grating is independent controlled.

34. according to the cross-connect of claim 16, wherein the wavelength variations that depends on temperature in the optical cross connect interchanger is that C is better less than the 0.05nm/100 degree less than 0.5nm/100 degree C.