CN2579093Y - Integrated rarefaction wave length division multiplexer - Google Patents

Abstract

The utility model discloses an integrated rarefaction wave division multiplexer. An output surface is arranged on a straight line via the special design of a color dispersing component, output optical fiber and an output optical fiber array are directly coupled with a free propagation area, and the manufacture of inputting and outputting waveguides is omitted. Compared with an original device, the size of a chip is reduced, and cost is decreased. The integrated rarefaction wave division multiplexer can obtain wide and flat frequency spectrum response via the adoption of multimode fiber output, and the integrated rarefaction wave division multiplexer is not sensitive to the deep movement of wavelength caused by temperature and polarization. The utility model is suitable for a rarefaction wave division multiplex light transmission system.

Description

Integrated-type coarse wavelength division multiplexer device

Technical field

The utility model relates to optical communication wavelength division multiplexing field, the particularly a kind of low cost of coarse wavelength division multiplexer, integrated-type plane wave division multiplexing device that spectral performance is good, manufacture craft is easy of being applicable to.

Background technology

Optical fiber communication obtains huge development at short many decades, and sharply expand recent years especially, and nowadays optical fiber has been routed to the every nook and cranny in the world.To a great extent, optical fiber has remedied the deficiency of cable communication, and message capacity and quality are increased greatly.Yet along with The development in society and economy, people are exponential increase to the demand of information, communication service also from phone, data to broadband business developments such as video, multimedias, the bandwidth of traditional optical transmission is also not enough.Fortunately on simple optical fiber, use wavelength division multiplexing (WDM) technology can become tens times, tens times, the increase power system capacity of hundreds of times, satisfy the demand that increases bandwidth.

Wavelength-division multiplex technique has now improved to such an extent that can transmit the laser of hundreds of wavelength, interval 1.6,0.8 or 0.4nm between each wavelength, even 0.2nm, and this technology is called dense wave division multipurpose (DWDM).The target of DWDM product is to satisfy ever-increasing long-distance transmission capacity requirement always, yet the market of the bandwidth dilatation of short distance net is also very huge, the wavelength-division multiplex technique that its one preferred technique is still ripe.The DWDM technology is used at wide area network and is obtained immense success, can certainly be applied in the lower short distance application of requirement, but this need pay expensive cost, surpasses new optical cable this " space division multiplexing " technology of laying.Therefore, can not be simply with wide area network DWDM scheme short distance net.

CWDM (Coarse Wavelength Division Multiplexing) coarse wave division multiplexing technology has been inherited the advantage of optical communication wavelength division multiplexing, provides short distance to use the dilatation technology that affords.CWDM adopt than DWDM sparse the wavelength interval of Duo, sacrificed the many advantages of number of active lanes among the DWDM, the while has also been abandoned the sky high cost of supporting that intensive passage is required, obtains service provider's price advantage that another presses for except that dilatation.Wide area network is because transmission range is very long, and a lot of amplifiers will be used in the centre, and dwdm system with intensive wavelength channel common optical fiber and amplifier, can reduce cost on very long distance significantly.The short distance net simply adopts the DWDM equipment the same with wide area network uneconomical because distance is short, and loss is not the principal element that influences performance, can not need to use amplifier yet.The CWDM technology is divided the very wide wavelength channel of frequency spectrum in the wideer loss window of optical fiber, can use no temperature control laser, and the also reduction greatly of requirement to filter can reduce cost significantly.

Demodulation multiplexer is the device of most critical in the division multiplex fibre-optic communication wave system.Existing realization technology mainly contains film filtering, fiber grating, plane integrated waveguide etc.Wherein plane integrated waveguide demodulation multiplexer can be in the dense wave division multipurpose that realizes on the very little chip more than 40 passages, and it utilizes semiconductor technology to produce in enormous quantities, has potential cost advantage.The high main cause of the integrated waveguide device costs in plane such as present array waveguide grating AWG is that size is big, and the core number that can make on each silicon chip is less; The requirement on devices strictness, rate of finished products is low; Need temperature control.

Realize that with the plane integrated technology report of coarse wavelength division multiplexer demodulation multiplexer is very few at present.McMullin etc. are at " Theory and simulation of a concave diffraction grating demultiplexerfor coarse WDM systems " Lightwave Technology, Journal of, Volume:20Issue:4, April 2002, Page (s): mention similar device among the 758-765, but it does not omit the input and output waveguide, there is no the size advantage.And adopt the multimode planar waveguide, and need very thick waveguide, increased the difficulty that technology is made, problems such as stress also can induce one.Owing to the existence of a plurality of patterns, it is all undesirable to assemble performance and spectral response simultaneously.

Summary of the invention

The purpose of this utility model provides a kind of integrated-type coarse wavelength division multiplexer device, has omitted the making of input and output waveguides, and basic technology is simple, and is with low cost and spectral performance is good.

The technology that the utility model adopts is as follows:

Scheme 1:

Integrated-type coarse wavelength division multiplexer device, it comprises free propagation zone, etching concave grating, input and output in free propagation zone adopt input optical fibre, output optical fibre array directly to be coupled respectively, input and output are on the cutting planes of chip, and input optical fibre and output optical fibre array are perpendicular to cutting planes.

Input adopts standard single-mode fiber, and free propagation zone adopts the single-mode plate waveguide, and output adopts the standard multimode fiber array.

Scheme 2:

Integrated-type coarse wavelength division multiplexer device, it comprises two free propagation zone, waveguide array, input and output two free propagation zone adopt input optical fibre, output optical fibre array directly to be coupled respectively, input and output are on the cutting planes of chip, and input optical fibre and output optical fibre array are perpendicular to cutting planes.

Input adopts standard single-mode fiber, and two free propagation zone adopt the single-mode plate waveguide, and output adopts the standard multimode fiber array.

The beneficial effect that the utlity model has is: demodulation multiplexer adopts the plane Integrated Waveguide Technology, adopts ripe semiconductor technology can realize the batch process of demultiplexing chip, is used to interfere the free propagation region of assembling light beam all to adopt the single-mode plate waveguide.The dispersive component of demodulation multiplexer is through special design different wave length to be accumulated on same the output straight line.Can omit input waveguide and output waveguide like this, make fiber array can be directly and the demultiplexing chip connect.Input optical fibre uses standard single-mode fiber carrying multi-wavelength signals, can transmit larger distance, and with the coupling efficiency height of single-mode plate waveguide, energy loss is little simultaneously.Output optical fibre adopts standard multimode fiber, the light of the single passage after the more acceptant chromatic dispersion of its big numerical aperture, and its big sandwich layer diameter can make output optical fibre can receive the light of very wide wave-length coverage, increased the bandwidth of passage, can omit the temperature control modules of demodulation multiplexer itself, reduce the volume of device, reduced cost and power consumption; Wavelength shift to various factors influence in the whole coarse wavelength division multiplexer system simultaneously has good tolerance.Simultaneously in this wide passage spectral response, the top flat of passband, the skew of wavelength is very little to the influence of power, has reduced greatly because the influence of the variable power that wavelength shift causes.The dispersion of demodulation multiplexer all is designed to be fit to the value of standard coarse wavelength division multiplexer wavelength interval and waveguide output spacing, makes compact arranged fiber array satisfy the requirement of coarse wavelength division multiplexer.Can be applied to the Wavelength Assignment of CWDM system, especially from monomode fiber to multimode fiber local area network (LAN) or Access Network; Also can be used for the transmission capacity that the CWDM transceiver increases simple optical fiber; Can realize coarse wavelength division multiplexer channel monitoring cheaply; In the passive network PON that optical fiber inserts, can be used as passive device multiplication bandwidth.

Description of drawings

Fig. 1 is based on the integrated-type coarse wavelength division multiplexer device structural representation of etched diffraction grating (EDG);

Fig. 2 is based on the integrated-type coarse wavelength division multiplexer device structural representation of array waveguide grating (AWG);

Fig. 3 is based on the dispersion characteristics of the integrated-type coarse wavelength division multiplexer device of etched diffraction grating (EDG);

Fig. 4 is based on each passage spectral response of the integrated-type coarse wavelength division multiplexer device of etched diffraction grating (EDG);

Fig. 5 is based on the channels uniformity of the integrated-type coarse wavelength division multiplexer device of etched diffraction grating (EDG).

Embodiment

Fig. 1 is an example of the present utility model, and the demodulation multiplexer structural representation based on the coarse wavelength division multiplexer of etched diffraction grating (EDG) comprises input optical fibre 1, output wave fiber array 2, free propagation region 3 and etching concave grating 4.The light signal that comprises a plurality of wavelength enters from input optical fibre 1, be coupled into free propagation region 3 in the junction of optical fiber connector and chip edge, light spreads propagation in free propagation region 3, light energy distribution is to each face of etching concave grating 4, the light of different wavelength accumulates in different output ports after reflecting partial wave and focusing on, and is derived by output optical fibre 2.

Fig. 2 is another example of the present utility model, and the demodulation multiplexer structural representation based on the coarse wavelength division multiplexer of array waveguide grating (AWG) comprises input optical fibre 5, output wave fiber array 6, two free propagation regions 7 and waveguide arrays 8.

Input optical fibre adopts standard single-mode fiber, and diameter is 125 microns of standard, about 9 microns of sandwich layer diameters.Output optical fibre adopts standard multi-module (62.5/125) optical fiber, 125 microns of external diameters, 62.5 microns of sandwich layer diameters.Other multimode fibers are as 50/125 micron, 100/140 micron also can use.The former can reduce the passband width of passage spectral response, and the latter has bigger passband width, but generally is not applied in the optical communication.

Here be that design example illustrates specific implementation form of the present utility model with demodulation multiplexer, and can use identical design fully based on the design of the demodulation multiplexer of array waveguide grating (AWG) based on etched diffraction grating (EDG).

The demultiplexing chip adopts semiconductor technology to plate film on silicon chip or other base materials, forms planar waveguide.Graphics chip shifts up the back cutting and forms single demultiplexing chip.Diffraction grating adopts dry etchings such as RIE and ICP, forms the reflecting grating that a plurality of vertical facets are formed.In order to reduce loss, increase reflectivity, can on the reflecting surface of etching moulding, plate the layer of metal reflector usually, perhaps, utilize total reflection to reduce transmission loss the rectangular V-arrangement tooth of grating face etching.

The design of grating here is vital, and it assembles point-blank the light of different wave length, and near the aberration specified point is very little, and it is linear that chromatic dispersion also keeps.Usually the structure of EDG is based on the design of Rowland circle, and incidence point and eye point are on the Rowland circle, and grating is being on the circle of radius with 2 times of Rowland radius of circles, and grating and Rowland circle are tangent.The light incident of different wave length can well be imaged on output point like this, and out of focus aberration on these aspects and coma are 0, and total aberration is very little.But the demodulation multiplexer of making does not need very strict aberration control, and we can reach the requirement that accumulates on the straight line by reducing the aberration requirement.

As shown in Figure 1, iconal can be written as:

Here I is an incidence point, and O is the output point on the vertical line.P0 is the reference point on the grating, P be on the grating more arbitrarily.Usually we only need the mid point of each reflection flank of tooth of definite grating just can obtain grating.Raised path between farm fields is integer value k with the value of getting G (x) like this, and P0 and P are also corresponding to be the mid point of the flank of tooth.Iconal can be written as like this:

F(k，λ)＝n _eff[IP _k+P _kO-(IP ₀+P ₀O)]-kmλ (2)

The coordinate of supposing these points is respectively I (x _I, y _I), O (x _O, y _O),

With So can increasing a variable, formula (2) write as: $F(k,\mathrm{\λ},y_O)=n_{\mathrm{eff}}\left[\begin{array}{c}\sqrt{{(x_I-x_{P_k})}^2+{(y_I-y_{P_k})}^2}+\sqrt{{(x_O-x_{P_k})}^2+{(y_O-y_{P_k})}^2}\\ -(\sqrt{{(x_I-x_{P_0})}^2+{(y_I-y_{P_0})}^2}+\sqrt{{(x_O-x_{P_0})}^2+{(y_O-y_{P_0})}^2})\end{array}\right]-\mathrm{km\λ}----\left(3\right)$

In order to reduce specified point on the well-behaved straight line Near the aberration of position imaging, the point on the grating Should satisfy equation $F(k,{\mathrm{\λ}}_0,y_{O_0})=0----\left(4\right)$

Here λ ₀Be the centre wavelength that accumulates in O0 point place.

Also to satisfy simultaneously

The derivative to y0 at some place is 0: $F^{\′}(k,{\mathrm{\λ}}_0,y_{O_0})=0----\left(5\right)$

According to formula (4), optical grating point Be with O0 and I on the ellipse that is focus (if O0 and I overlap, then on circle).

Make that x=0 is on the straight line at input and output point place, formula (5) can be expressed as: $F^{\′}(k,{\mathrm{\λ}}_0,y_{O_0})=n_{\mathrm{eff}}\left[\begin{array}{c}(y_{O_0}-y_{P_k})/\sqrt{{(x_{O_0}-x_{P_k})}^2+{(y_{O_0}-y_{P_k})}^2}\\ -(y_{O_0}-y_{P_0})/\sqrt{{(x_{O_0}-x_{P_0})}^2+{(y_{O_0}-y_{P_0})}^2}\end{array}\right]-\mathrm{kmD}----\left(6\right)$

Here $D=\frac{\mathrm{d\λ}}{{\mathrm{dy}}_O}{|}_{y_O=y_{O_0},}$ It is the dispersive power of grating.

(5), (6) two equations have been determined the center position that grating is all, add that on these aspects the whole grating of grating face is just definite.

Here provide the design example of this example:

Design parameter	Value
		Input point (μ m): I	(0，0)
Grating reference point (μ m): P0	(8000，0)
		Specify output point (μ m): O	(0，-500)
Design wavelength (nm): λ 0	1550
		Grating exponent number: m	8
Chromatic dispersion (μ m/nm): D	6.25
		Planar waveguide effective refractive index: neff	1.47
Channel spacing (nm)	20
		Port number	8

Here effective refractive index gets 1.47, is to use the SiO 2 waveguide material of normal use.We are with the performance of more accurate scalar diffraction theory analog computation EDG, the analog parameter of use:

Input gauss light beam waist (um): w0	10
		Output plane (um):	X＝0；y＝-1100～100；
Output multimode fiber structure (um/um): sandwich layer/covering	62.5/125
		Channel center's wavelength (nm):	1470nm is to 1610nm interval 20nm

Fig. 3 is the dispersion curve of grating, sees that to draw the linearity fine, and 6.25 μ m/nm are very approaching with design load.But along with the scope of output increases, the linearity can variation, because the output area is here compared big many of the EDG of traditional band output waveguide.However, the output area here, linearity keep finely.

Fig. 4 is the spectral response of 8 passages.Passband is very wide as can be seen, and the top is very flat, ripple in almost not being with.This is because multimode fiber has big sandwich layer diameter.Such characteristic is highly suitable for the application of CWDM.For central passage, the supplementary load loss of 0.03dB have only been introduced.The three dB bandwidth of each passage is 10nm also much at one.

Fig. 5 has shown the uniformity of passage, and maximum loss difference is 1.5dB.Can see that loss is along with increasing away from central passage.This is that diffraction envelope by single grating tooth is determined.If the grating flank of tooth reduces, uniformity can increase, but can increase the difficulty that technology is made like this.

Claims (4)

1. integrated-type coarse wavelength division multiplexer device, it comprises free propagation zone (3), etching concave grating (4), it is characterized in that: input and output in free propagation zone (3) adopt the directly coupling of input optical fibre (1), output optical fibre array (2) respectively, input and output are on the cutting planes of chip, and input optical fibre and output optical fibre array are perpendicular to cutting planes.

2. according to the described integrated-type coarse wavelength division multiplexer of claim 1 device, it is characterized in that: input adopts standard single-mode fiber, and free propagation zone (3) adopts the single-mode plate waveguide, and output adopts the standard multimode fiber array.

3. integrated-type coarse wavelength division multiplexer device, it comprises two free propagation zone (7), waveguide array (8), it is characterized in that: input and output in two free propagation zone (7) adopt the directly coupling of input optical fibre (5), output optical fibre array (6) respectively, input and output are on the cutting planes of chip, and input optical fibre and output optical fibre array are perpendicular to cutting planes.

4. according to the described integrated-type coarse wavelength division multiplexer of claim 3 device, it is characterized in that: input adopts standard single-mode fiber, and two free propagation zone (7) adopt the single-mode plate waveguide, and output adopts the standard multimode fiber array.

Images