KR100566853B1 - Apparatus which includes a virtually images phased array (vipa) in combination with a wavelength splitter to demultiplex a wavelength division multiplexed (wdm) light - Google Patents

Abstract

A device is disclosed that combines a virtually imaged phased array (VIPA) with a demultiplexer to operate as a wide bandwidth, high resolution wavelength demultiplexer. In general, VIPA is a device that receives incident light having respective wavelengths within a continuous wavelength range and causes multiple reflections of the incident light, thereby generating self-interference to form the emitted light. The outgoing light is spatially distinguishable from the outgoing light formed by the incident light having any other wavelength within the continuous wavelength range. The device combines VIPA with a demultiplexer such as a diffraction grating. More specifically, VIPA receives incident light and generates corresponding outgoing light propagating from VIPA. The emitted light includes a number of different wavelength components. The demultiplexer demultiplexes the emitted light into a plurality of separate lights, each corresponding to a plurality of different wavelength components of the emitted light. The dispersion direction of the demultiplexer is preferably perpendicular to the dispersion direction of VIPA. In this case, the separated light from the demultiplexer can be detected by the optical fibers arranged in a grid pattern.

Description

FIELD OF COMBINATION WITH A WAVELENGTH SPLITTER TO DEMULTIPLEX A WAVELENGTH DIVISION MULTIPLEXED (WDM) LIGHT}

The present invention relates to an apparatus comprising a Virtually Imaged Phased Array (VIPA) for demultiplexing Wavelength Division Multiplexed (WDM) light. More specifically, the present invention relates to an apparatus comprising VIPA coupled with a wavelength divider, such as a diffraction grating, to accurately demultiplex wavelength-division multiplexed light having a relatively large number of dense wavelength components.

In order to transmit relatively large amounts of data at high speed, a wavelength division multiplexing technique is used in an optical fiber communication system. More specifically, a plurality of carriers modulated with respective information are combined into wavelength division multiplexed light. The wavelength division multiplexed light is then transmitted to the receiver via a single optical fiber. To detect each carrier, the receiver splits the wavelength division multiplexed light into respective carriers. In this way, the communication system transmits a relatively large amount of data through one optical fiber.

Thus, the receiver's ability to accurately split wavelength division multiplexed light will greatly affect the performance of the system. For example, even if a large number of carriers can be combined into one wavelength division multiplexed light, such wavelength division multiplexed light will not be transmitted unless the receiver can accurately divide the wavelength division multiplexed light. It is therefore desirable for the receiver to have a high-precision wavelength splitter.

1 is a diagram illustrating a conventional filter using a multi-layer interface film as a wavelength divider. As shown in FIG. 1, the multilayer interference film 20 is formed on the transparent substrate 22. Light 24, which must be parallel light, enters the film 20 and is repeatedly reflected in the film 20. Due to the optical conditions determined by the properties of the film 20, only the light 26 with wavelength lambda 2 passes through the film. Light 28, which includes all light that does not satisfy the optical conditions, is reflected through the film 20 without passing through it. Therefore, the filter as shown in FIG. 1 is useful in the case of splitting wavelength division multiplexed light including only two carrier waves having different wavelengths? 1 and? 2. Unfortunately, such a filter alone cannot separate wavelength division multiplexed light having three or more carriers.

FIG. 2 shows a conventional Fabry-Perot interferometer used as a wavelength divider. As shown in FIG. 2, the high reflectivity reflecting films 30 and 32 are located parallel to each other. Light 34, which should be parallel light, enters the reflecting film 30 and is reflected several times between the reflecting films 30 and 32. Light 36 having a wavelength? 2 that satisfies the pass condition determined by the characteristics of the Fabry-Perot interferometer passes through the reflective film 32. Light 38 having wavelength lambda 1 that does not satisfy the pass condition is reflected. In this way, light having two different wavelengths can be split into two different lights corresponding to each of the two different wavelengths. Thus, similarly to the filter shown in FIG. 1, the conventional Fabry-Perot interferometer is useful in the case of splitting wavelength division multiplexed light including only two carriers having different wavelengths? 1 and? 2. Unfortunately, these Fabry-Perot interferometers cannot separate wavelength division multiplexed light having three or more carriers.

3 is a diagram illustrating a conventional Michelson interferometer used as a wavelength divider. As shown in FIG. 3, the parallel light 40 is incident on the translucent glass 42 and then separated into first light 44 and second light 46 that are perpendicular to each other. Reflective mirror 48 reflects first light 44, and reflecting mirror 50 reflects second light 46. The distance between the translucent glass 42 and the reflecting mirror 48 and the distance between the translucent glass 42 and the reflecting mirror 50 represent the optical path difference. Light reflected by the reflecting mirror 48 and returned to the translucent glass 42 interferes with light reflected by the reflecting mirror 50 and returned to the translucent glass 42. As a result, the lights 52 and 54 having wavelengths λ1 and λ2, respectively, are separated from each other. Like the filter shown in FIG. 1 and the Fabry-Perot interferometer shown in FIG. 2, the Michelson interferometer shown in FIG. 3 divides the wavelength division multiplexed light including only two carriers having different wavelengths λ 1 and λ 2. Useful for Unfortunately, such Michelson interferometers cannot separate wavelength division multiplexed light having three or more carriers.

It is also possible to combine multiple filters, Fabry-Perot interferometers, or Mickelson interferometers into one large array to separate carriers of additional wavelengths from a single wavelength division multiplexed light. However, such an array is expensive, inefficient, and the receiver becomes undesirably large.

Diffraction gratings or array waveguide gratings are often used to split wavelength-division multiplexed light comprising carrier waves of two or more wavelengths.

4 is a diagram illustrating a conventional diffraction grating for splitting wavelength division multiplexed light. As shown in FIG. 4, the diffraction grating 56 includes a grating surface 58. Parallel light 60 comprising a plurality of different wavelength carriers is incident on the grating surface 58. Carriers of different wavelengths are reflected at each step of the grating surface 58 to interfere with each other. As a result, carriers 62, 64 and 66 of different wavelengths are emitted from the diffraction grating 56 at different angles and thus are separated from each other.

Unfortunately, the diffraction grating outputs carriers of different wavelengths at relatively small dispersion angles. As a result, it becomes difficult for the receiver to correctly receive the various carrier signals divided by the diffraction grating. This problem is particularly acute in diffraction gratings that split wavelength-division multiplexed light comprising many carriers of relatively dense wavelengths. In this case, the angle of dispersion by the diffraction grating will be extremely small, with 0.05degree / nm being typical.

Moreover, the diffraction grating is affected by the polarization of the incident light. Thus, polarization of incident light can affect the performance of the diffraction grating. In addition, in order to produce an accurate diffraction grating, a complicated manufacturing process is required in the manufacture of the grating surface.

FIG. 5 illustrates a conventional array waveguide grating for splitting wavelength division multiplexed light. As shown in FIG. 5, light including a plurality of carriers of different wavelengths is received through an inlet 68 and split into a plurality of waveguides 70. A light exit 72 is located at the end of each waveguide 70, so that light 74 is emitted. Since the waveguides 70 are different in length from each other, they provide optical paths of different lengths. Thus, since the phases of light passing through the waveguide 70 are different, interference occurs with each other when exiting through the outlet 74. Due to this interference, light having different wavelengths is emitted in different directions.

In an array waveguide grating, the angle of dispersion can be adjusted to some degree with proper placement of the waveguide. However, array waveguide gratings are affected by temperature variations and other peripheral factors. Therefore, it is difficult to properly adjust the dispersion angle due to temperature changes and surrounding factors.

It is an object of the present invention to provide a simple type of wavelength divider capable of simultaneously separating multiple carriers from wavelength division multiplexed light.

It is still another object of the present invention to provide an apparatus for accurately demultiplexing wavelength division multiplexed light having a relatively large number of dense carriers or wavelength components.

An object of the present invention can be achieved by an apparatus that receives incident light having respective wavelengths within a continuous wavelength range and generates corresponding outgoing light. The emitted light is spatially distinguishable from the emitted light formed by the incident light having any other wavelength within the continuous wavelength range (for example, the traveling direction is different).

In more detail, the device receives incident light having respective wavelengths within a continuous wavelength range, causing multiple reflections of the incident light, thereby causing self-interference and consequently forming outgoing light. The emitted light is spatially distinguishable from the emitted light formed by the incident light having any other wavelength within the continuous wavelength range. This device is called a Virtually Imaged Phased Array (VIPA).

In addition, the object of the present invention can be achieved by a device combining VIPA with a wavelength divider or demultiplexer such as a diffraction grating. More specifically, the VIPA receives incident light and generates corresponding outgoing light propagating from the VIPA. The emitted light includes a number of different wavelength components, such as different carriers. The demultiplexer demultiplexes the emitted light into a plurality of separate lights, each corresponding to a plurality of different wavelength components of the emitted light. The dispersion direction of the demultiplexer is preferably substantially perpendicular to the dispersion direction of VIPA. In this case, the separated light from the demultiplexer can be detected by the optical fibers arranged in a grid pattern.

In addition, an object of the present invention can be achieved by an apparatus for demultiplexing incident light including a plurality of lights. Each wavelength of the plurality of lights is different from each other. The apparatus includes first and second demultiplexers. The first demultiplexer demultiplexes the incident light into a plurality of output lights respectively corresponding to the plurality of lights included in the incident light. The first demultiplexer distributes a plurality of outgoing lights at different outgoing angles for each outgoing light along a substantially linear dispersion direction. In addition, each emitted light includes a plurality of wavelength components. The second demultiplexer demultiplexes each outgoing light into a plurality of separate lights, each corresponding to a plurality of wavelength components included in the outgoing light. The second demultiplexer distributes the plurality of separated lights at different exit angles for each of the separated lights along a nearly linear dispersion direction. The dispersion direction of the second demultiplexer is not parallel to the dispersion direction of the first demultiplexer and is preferably vertical.

6 is a diagram illustrating a virtually imaged phased array (VIPA) according to an embodiment of the present invention. The terms "wavelength divider", "phantom phase array", or "VIPA" are used interchangeably herein.

As shown in FIG. 6, the VIPA 76 is preferably made of a thin glass plate. Incident light 77 is focused on straight line 78 by lens 80, such as a semi-cylindrical lens, and travels into VIPA 76. Straight line 78 is hereinafter referred to as " focal line 78 ". The incident light 77 propagates radially from the focal line 78 and is received into the VIPA 76. VIPA 78 then outputs a light emitting flux 82 of collimated light, the emission angle of light emitting flux 82 changing as the wavelength of incident light 77 changes. For example, when the wavelength of the incident light 77 is λ 1, the VIPA 76 emits the light emission flux 82a having the wavelength λ 1 in a specific direction. When the wavelength of the incident light 77 is lambda 2, the VIPA 76 outputs the light emission flux 82b having the wavelength lambda 2 in the other direction. If the incident light 77 is wavelength division multiplexed light in which light having a wavelength of λ1 and light having a wavelength of λ2 is combined, the VIPA 76 simultaneously emits two separate light emitting fluxes 82a and 82b in different directions. . Accordingly, the VIPA 76 generates light emitting fluxes 82a and 82b which are spatially distinguishable from each other. In this way, VIPA 76 can simultaneously separate two or more different carriers from wavelength division multiplexed light.

FIG. 7 is a cross-sectional view along line VII-VII of VIPA 76 shown in FIG. 6, in accordance with an embodiment of the invention. As shown in FIG. 7, VIPA 76 is comprised of a material 84, such as glass, having reflective surfaces 86, 88 on its surface. Reflecting surfaces 86 and 88 are parallel to each other and spaced apart at a distance t. Typical reflective surfaces 86 and 88 are vapor deposited reflective films on material 84. The reflective surface 88 has a reflectance of about 100%, with the exception of the radiation window 90 described below in more detail. Reflecting surface 86 has a reflectance of about 95%. Therefore, since the reflective surface 86 has a transmittance of about 5%, about 5% of the light incident on the reflective surface 86 passes through the reflective surface 86, and about 95% of the light will be reflected. Depending on the application of the particular VIPA, the reflectance can be easily changed. However, in general, the reflective surface 86 should have a reflectance of less than 100% so that some of the incident light can be transmitted.

The reflective surface 88 has a radiation window 90 on its surface. The radiation window 90 allows light to pass through and preferably has no or very low reflectance. The radiation window 90 receives the incident light 92 so that the incident light 92 can enter between the reflective surfaces 86 and 88 and be reflected therebetween.

FIG. 7 shows a cross section along line VII-VII in FIG. 6, so the focal line 78 of FIG. 6 is represented by a dot in FIG. 7. Incident light 92 propagates radially from the focal line 78. In addition, as shown in FIG. 7, the focal line 78 is positioned on the reflective surface 86. Although it is not required for the focal line to be located on the reflective surface 86, shifting the position of the focal line 78 may cause a small change in the characteristics of the VIPA 76.

As shown in FIG. 7, incident light 92 enters material 84 through region A0 in radiation window 90, with point P0 representing the boundary point of region A0.

By the reflectance of the reflecting surface 86, light of about 5% or less of the incident light 92 passes through the reflecting surface 86 as the transmitted light OUT0 defined by the ray R0, and about 95% or more of the incident light 92 Light is reflected by the reflection surface 86 and is incident on the area A1 of the reflection surface 88. The point P1 represents the boundary point of the area A1. After being reflected in the area A1 of the reflecting surface 88, the incident light 92 proceeds to the reflecting surface 86 and partially passes through the reflecting surface 86, such as the transmitted light OUT1 defined by the light ray R1. In this manner, as shown in FIG. 7, incident light 92 is multiplely reflected between reflective surfaces 86 and 88, and each transmitted light is reflected from reflective surface 86 to each reflective beam 86. Permeate. Thus, for example, immediately after the incident light 92 is reflected in the areas A2, A3, and A4 on the reflecting surface 88, the incident light 92 is reflected on the reflecting surface 86 while the respective transmitted light Out2, Out3 is reflected. , And Out4 occurs. Point P2 indicates the boundary point of the area A2, point P3 indicates the boundary point of the area A3, and point P4 indicates the boundary point of the area A4. The transmitted light Out2 is defined by the light beam R2, the transmitted light Out3 is defined by the light beam R3, and the transmitted light Out4 is defined by the light beam R4. Although only transmitted light Out0, Out1, Out2, Out3, and Out4 are shown in FIG. 7, depending on the power of the incident light 92 and the reflectivity of the reflecting surfaces 86, 88, there will actually be a larger number of transmitted light.

As will be described later in more detail, interference occurs between transmitted light and light emission flux is emitted. The direction of the outgoing light changes depending on the wavelength of the incident light 92.

7 shows an example of incident light composed of a single wavelength. However, even if the incident light is composed of a plurality of wavelengths (eg, wavelength division multiplexed light, each of which consists of a plurality of different carriers, the wavelength), the incident light will be reflected in the same manner. However, a plurality of light emitting fluxes, each corresponding to a plurality of carriers, will be formed. Each luminous flux will exit the VIPA at a different angle than the other luminous flux.

8 is a diagram illustrating interference between reflected waves generated from VIPA according to an embodiment of the present invention. As shown in FIG. 8, light propagating from the focal line 78 is reflected at the reflecting surface 88 and then reflected at the reflecting surface 86. As mentioned above, the reflecting surface 88 has a reflectivity of approximately 100% and thus essentially functions as a mirror. As a result, the transmitted light Out1 can be optically analyzed as the reflection surfaces 86 and 88 do not exist and instead are emitted from the focal line I1. Likewise, transmitted light Out2, Out3, and Out4 can be optically analyzed as being emitted from focal lines I2, I3, and I4, respectively. Focal lines I1, I2, I3, and I4 are virtual images of focal line I0.

Thus, as shown in FIG. 8, the focal line I1 is 2t away from the focal line I0, where t is equal to the distance between the reflecting surfaces 86, 88. Likewise, each of the subsequent focal lines is 2t away from the immediately preceding focal line. Therefore, the focal line I2 is separated by a distance 2t from the focal line I1. In addition, each of the subsequent multiple reflections between the reflecting surfaces 86 and 88 generates transmitted light having a lower intensity than the previous transmitted light. Therefore, transmitted light Out2 is weaker in intensity than transmitted light Out1.

As shown in FIG. 8, the transmitted light propagating from the focal lines overlap and interfere with each other. Moreover, since the focal lines I1, I2, I3, and I4 are the virtual images of the focal line I0, the transmitted light Out0, Out1, Out2, Out3, and Out4 have the same optical phase at the positions of the focal lines I0, I1, I2, I3, and I4. Has Therefore, the light emission flux traveling in a specific direction according to the wavelength of the incident light 92 is generated by the interference.

VIPA according to this embodiment of the present invention has a strength condition (strengthening condition) which is a design characteristic of VIPA. Depending on the strengthening conditions, interference of transmitted light is increased to form a light emission flux. The reinforcement condition of VIPA is represented by the following equation (1).

2t * cosψ = mλ

Is a value measured from a straight line perpendicular to the surfaces of the reflecting surfaces 86 and 88. λ denotes the wavelength of the incident light, t denotes the distance between the reflecting surfaces 86 and 88, and m denotes an integer.

Therefore, if t is a constant and a specific value is assigned to m, the propagation direction ψ of the light emission flux formed by the incident light having the wavelength λ can be determined.

More specifically, the incident light is distributed radially from the focal line 78 along a particular angle. Thus, incident light having the same wavelength will travel from the focal line 78 in various directions and be reflected between the reflective surfaces 86 and 88. Light traveling in a particular direction by the strengthening conditions of the VIPA will be enhanced by interference between the transmitted light, thereby forming a light emitting flux having a direction corresponding to the wavelength of the incident light. Light traveling in a direction different from the specific direction required by the strengthening condition is weakened by interference between the transmitted light.

Moreover, if the incident light includes light having a plurality of different wavelengths, different light emission fluxes will be formed for each wavelength of the incident light by the strengthening condition. Each light emitting flux will have a different wavelength from each other. Accordingly, the VIPA receives the wavelength division multiplexed light, and proceeds in different directions, and generates a plurality of emission fluxes corresponding to various wavelengths of the wavelength division multiplexed light.

FIG. 9 is a diagram showing the structure of the light emitting flux by VIPA 76, in accordance with an embodiment of the present invention, showing a cross section along line VII of FIG. More specifically, FIG. 9 shows that VIPA 76 forms multiple light emitting fluxes, each having a different propagation direction depending on the wavelength of incident light.

As shown in FIG. 9, incident light having a plurality of wavelengths is radially dispersed from the focal line 78 and reflected between the reflecting surfaces 86 and 88. Assume that the incident light includes light having three different wavelengths. Thus, light having each wavelength will be dispersed in various directions from the focal line 78. By the strengthening conditions of the VIPA 76, the light having the same wavelength and traveling in a specific direction is enhanced by the light traveling in different directions, thereby forming a light emission flux having a direction corresponding to the wavelength of the incident light. Thus, for example, the light traveling in the direction θ1 from the focal line 78 with the wavelength λ1 will be enhanced by the light traveling in the other direction, thereby forming the light emission flux LF1 having the propagation direction θ1. Similarly, the light traveling in the direction θ2 from the focal line 78 with the wavelength λ2 will be enhanced by the light traveling in the other direction to form the light emission flux LF2 having the propagation direction θ2. Further, the light traveling in the direction θ3 from the focal line 78 with the wavelength λ3 will be enhanced by the light traveling in the other direction to form the light emission flux LF3 having the propagation direction θ3.

As mentioned above, equation (1) must be satisfied to increase the interference between the transmitted light forming the light emission flux. In addition, the thickness t of the material 84 is appropriately fixed. Therefore, the range of the incident angle of the incident light must be determined so that the incident light can enter the VIPA 76 in the propagation direction ψ satisfying equation (1). More specifically, the propagation direction of incident light can be fixed, the distance t between the reflective surfaces 86 and 88 can be fixed, and the wavelength of the incident light can be predetermined. Thus, the specific angle of the emitted light flux for each wavelength of the incident light can be determined, and it can satisfy the strengthening condition of the VIPA 76.

Moreover, since the incident light is distributed in various directions from the focal line 78, it is ensured that the incident light propagates in a direction that satisfies the strengthening condition.

FIG. 10 is a cross-sectional view along the line VII-VII of the VIPA shown in FIG. 6, in accordance with an embodiment of the present invention, illustrating the characteristics of the VIPA for determining the incident angle or tilt angle of the incident light; FIG. Drawing.

As shown in FIG. 10, the incident light 92 is collected by a cylindrical lens (not shown in FIG. 10) and focused on the focal line 78. As shown in FIG. 10, incident light 92 includes a region of width “a” above radiation window 90. After incident light 92 is reflected once at reflective surface 86, incident light 92 is incident on reflective surface 88 and includes a region of width “b” on reflective surface 88. In addition, as shown in FIG. 10, the incident light 92 travels along the optical axis 94 whose inclination angle with respect to the vertical of the reflection surface 86 is θ1.

The inclination angle θ1 prevents the incident light 92 from traveling out of the material 84 through the radiation window 90 when the incident light 92 enters VIPA, and after the incident light 92 is first reflected on the reflective surface 86, the reflective surface ( 88) The angle is determined so that it can be prevented from going outside. In other words, the inclination angle θ1 is determined so that the incident light 92 remains “trapped” between the reflecting surfaces 86, 88 and does not exit through the radiation window 90. Therefore, in order to prevent the incident light 92 from traveling out of the material 84 through the radiation window 90, the inclination angle θ1 should be determined according to the following equation (2).

Tilt angle of the optical axis θ1 ≥ (a + b) / 4t

Thus, as illustrated in FIGS. 6 to 10, the implementation of the present invention includes VIPA for receiving incident light having respective wavelengths within a continuous wavelength range. VIPA causes multiple reflections of incident light, causing self-interference to form the outgoing light. The emitted light is also spatially distinguishable from the emitted light formed by incident light of any other wavelength within the continuous wavelength range. For example, incident light 92 that is multiplely reflected between reflective surfaces 86 and 88 is shown in FIG. By this multiple reflection, a plurality of transmitted light Out0, Out1, Out2, Out3, and Out4 are generated, and the transmitted light interferes with each other to form a light emitting flux such as light emitting flux LF1, LF2, or LF3 shown in FIG.

"Self-interference" is a term that indicates when interference occurs between light or beams from the same light source. Thus, interference between transmitted light Out0, Out1, Out2, Out3, and Out4 can be regarded as self-interference of incident light 92, because transmitted light Out0, Out1, Out2, Out3, and Out4 are all the same light source, i.e., incident light. This is because it occurs from (92).

According to the above embodiment of the present invention, the wavelength of the incident light can be any wavelength within the continuous wavelength range. Thus, the wavelength of incident light is not limited to the wavelength selected in the range of discretized values.

Further, according to the embodiment of the present invention, the emitted light generated by incident light of a specific wavelength within the continuous wavelength range can be spatially distinguished from the emitted light generated by incident light of another wavelength within the continuous wavelength range. Thus, for example, as shown in FIG. 6, the advancing direction of the light emitting flux 82-that is, the spatial characteristic-differs from the advancing direction when the incident light 77 is another wavelength within the continuous wavelength range. . The above operation is compared with the conventional wavelength dividing apparatus shown in Figs. 1 to 3, in which the incident light of two different wavelengths of incident light is spatially distinguishable, but the incident light of wavelengths within the continuous wavelength range. It does not generate spatially distinguishable outgoing light. For example, in the case of the filter shown in FIG. 1, all carriers whose wavelength is not λ 2 in the wavelength division multiplexed light will be the emitted light 28.

FIG. 11 is a diagram illustrating VIPA used with a receiver, in accordance with an embodiment of the present invention. FIG. As shown in Fig. 11, multilayer reflective films 96 and 98 are adhered to both sides of a flat plate 100 made of glass having a thickness t-for example, 100 mu m. The thickness of the plate is preferably in the range of 20 µm to 2000 µm. The reflective films 96 and 98 are preferably multilayer high reflectivity interference films.

The reflectance of the reflective film 98 is approximately 100%, and the reflectance of the reflective film 96 is approximately 95%. However, the reflectance of the reflective film 96 is not limited to 95%, and other values are possible as long as enough light is reflected to allow multiple reflections between the reflective films 96 and 98. The reflectance of the reflective film 96 is preferably in the range of 80% to less than several percent from 100%. In addition, the reflectance of the reflective film 98 is also not limited to 100%, but should be sufficiently high so that multiple reflections can occur between the reflective films 96 and 98.

The radiation window 102 receives incident light and is positioned on the same surface as the reflective film 96 on the flat plate 100. Radiation window 102 may be formed on the surface of flat plate 100 by a film having a reflectance of approximately 0%. As shown in FIG. 11, the boundary between the radiation window 102 and the reflective film 96 is preferably a straight line.

Incident light is, for example, output from an optical fiber, not shown, which is received by the collimating lens 106. The collimating lens 106 converts incident light into parallel light, and the parallel light is received by the cylindrical lens 108. The cylindrical lens 108 focuses the parallel light 104 on the reflecting film 98 or on a focal line 110 located at a point inside the flat plate 100. In this way, incident light enters the flat plate 100 through the radiation window 102.

The optical axis of the incident light is inclined by an inclination angle with respect to the vertical line of the reflective film 96 so that the incident light does not leak through the radiation window 102 after entering the flat plate 100. Therefore, the inclination angle is determined by the above equation (2).

After entering the inside of the flat plate 100, incident light is multiplely reflected between the reflective films 96 and 98 as illustrated in FIG. Each time incident light enters the reflecting surface 96, approximately 95% of the light is reflected toward the reflecting surface 98, and approximately 5% of the light passes through the reflecting film 96 and the transmitted light Out1 illustrated in FIG. The same transmitted light is formed. Multiple transmitted light is formed by multiple reflections between the reflective films 96 and 98. The plurality of transmitted lights interfere with each other to form a light emission flux 112 having a propagation direction that depends on the wavelength of the incident light.

The light emitting flux 112 is then condensed by the lens 114 and condensed at the condensing point. The location of the focusing point moves along the straight path 116 as the wavelength of the incident light varies. For example, as the wavelength of incident light increases, the focusing point moves further along the straight path 116. In order to receive the focused light emitting flux 12, a number of receivers 118 are arranged along a straight path 116. Thus, each receiver 118 may be positioned to receive light emission flux corresponding to a particular wavelength.

By adjusting the distance t between the reflective film or the reflective surface of the VIPA, the phase difference of the reflected light between the reflective film or the reflective surface can be shifted by a predetermined amount, so that excellent environmental resistance is achieved. Moreover, in the above embodiment of the present invention, the optical properties only slightly change depending on the polarization.

12 is a diagram illustrating VIPA used with a receiver, in accordance with a further embodiment of the present invention. The VIPA shown in FIG. 12 is similar to the VIPA shown in FIG. 11 except that the reflectances of the reflecting films 96 and 98 are reversed from each other. More specifically, in the VIPA shown in FIG. 12, the reflective film 98 has a reflectance of approximately 95% and the reflective film 96 has a reflectance of approximately 100%. As shown in FIG. 12, the light emission flux 112 is formed by interference between transmitted light passing through the reflective film 98. Accordingly, incident light is incident on one side of the flat plate 100, and the light emission flux 112 is formed on the opposite side of the flat plate 100. Otherwise, the VIPA shown in FIG. 12 operates in a similar manner to the VIPA shown in FIG.

13 illustrates a VIPA according to another embodiment of the present invention. As shown in FIG. 13, there are reflective films 122, 124 on top of a plate 120 made of a material such as glass. The reflectivity of the reflective film 122 is approximately 95% or more and less than 100%. The reflectance of the reflective film 124 is approximately 100%. The reflectance of the reflecting window 126 is approximately 0%.

The incident light 128 is focused on the focal line 129 by the cylindrical lens 130 via the radiation window 126. The focal line 129 is positioned on the surface to which the reflective film 122 of the plate 120 is attached. Thus, the focal line 129 is essentially a line focused on the reflective film 122 via the radiation window 126. The width of the focal line 129 may be referred to as the "beam waist" of the incident light 128 focused by the cylindrical lens 13. As such, in the embodiment of the present invention shown in FIG. 13, the ray waist of the incident light 128 is concentrated on the distant surface of the plate 120, that is, the surface on which the reflective film 122 is located. By concentrating the ray waist on a distant surface of the plate 120, this embodiment of the present invention reduces the likelihood of overlapping the next two regions, which (i) the radiation window 126 on the surface of the plate 120. Of the area covered by the incident light 128 traveling through the radiation window 126, for example the area " a " shown in FIG. 10, and (ii) of the reflective surface 124 In the region, the incident light 128 is first reflected by the reflective film 122 and then covered by the incident light 128-for example, the region " b " shown in FIG. It is desirable to reduce the redundant area to ensure proper operation of the VIPA.

In FIG. 13, the optical axis 132 of the incident light 128 has a small tilt angle θ. In the first reflection at the reflecting surface 122, 5% of light passes through the reflecting film 122 and diverges behind the ray waist, and 95% of light is reflected towards the reflecting surface 124. After the first reflection by the reflective film 124, the light is displaced by the value of d proceeds to the reflective film 122 again. 5% of light passes through the reflective film 122. In a similar manner, as shown in FIG. 13, light is divided into many paths by a constant d apart. The shape of the light for each path is formed as the light diverges from the virtual images 134 of the ray waist 129. The virtual images 134 are located a distance of 2t apart along a vertical line of the plate, where t is the thickness of the plate 120. The position of the ray waist in the virtual image 134 is self-aligned and there is no need to adjust each position. Thereafter, the light diverging from the virtual image 134 interferes with each other to form collimated light 136, which is propagated in a direction that changes depending on the wavelength of the incident light 128.

The distance between the optical paths is d = 2tsinθ, and the difference in path length between adjacent light beams is 2tcosθ. Each variance is proportional to the ratio of these two values, which is cotθ. As a result, in comparison to the conventional wavelength divider, by the embodiment of the present invention, a considerably large angular dispersion occurs between light emission fluxes for different carriers.

As mentioned above, the device implemented by the present invention is referred to as a "virtual phase array". As shown in FIG. 13, the name “imaginary phase array” comes from the structure of an array of virtual images 134.

14 is a diagram illustrating waveguide type VIPA, in accordance with an embodiment of the present invention. As shown in FIG. 14, light 138 is received by the waveguide 140 provided from the optical fiber, not shown, and provided over the substrate 142. The waveguide 140 is made of, for example, lithium niobate. Light 138 includes an optical signal modulated with multiple carriers having different wavelengths.

Light 138 typically comes from the optical fiber and has a dispersion width. Thus, the collimating lens 142 converts the light 138 into parallel light. Parallel light is then focused by the cylindrical lens 144 and concentrated at the focal line 146. Light is then emitted from the focal line 146 through the radiation window 150 into the VIPA 148.

VIPA 148 is composed of reflective films 152 and 154 on flat plate 156. The reflective film 154 is located on one side of the flat plate 156, and the reflective film 152 and the radiation window 150 are located on the other side of the flat plate 156. The reflectance of the reflective film 152 is approximately 100%, and the reflectance of the reflective film 154 is less than 100%. The light emission flux 158 of the light reflected from the flat plate 156 exits to the opposite side of the radiation window 150 of the flat plate 156.

If the incident light 138 includes a plurality of wavelengths, a plurality of light emitting fluxes 158 traveling in different directions depending on the wavelength of the incident light 138 will be formed. The luminous flux 158 formed by the VIPA 148 will be concentrated at different points by the lens 160 depending on the propagation direction of the luminous flux 158. Thus, as shown in Fig. 14, light emission fluxes 158a, 158b, and 158c having wavelengths λ1, λ2, and λ3, respectively, will be formed at different light collection points.

The focusing point is provided with a plurality of receiving waveguides 162. Each receiving waveguide 162 induces an optical signal and a corresponding carrier signal having a single wavelength. Thus, multiple light emitting fluxes can be received simultaneously and transmitted on various channels. At the back end of each waveguide is provided a corresponding receiver, not shown. The receiver is typically a photodiode. Thus, the light guided by each receiving waveguide 162 is processed after being detected by the corresponding receiver.

15A, 15B, 15C, and 15D are diagrams illustrating a method for manufacturing VIPA, in accordance with an embodiment of the present invention. As shown in FIG. 15A, the plate 164 is preferably made of glass and exhibits excellent parallelism. Reflective films 166 and 168 are formed on both sides of flat plate 164 by vacuum deposition, ion sputtering, or other methods. The reflectance of one of the reflecting films 166 and 168 is almost 100%, and the reflectance of the other reflecting film is less than 100%, preferably 80% or more.

As shown in FIG. 15B, one of the reflective films 166, 168 is partially removed to form the radiation window 170. In FIG. 15B, it is shown that the reflective film 166 is removed so that the radiation window 170 is formed on the same surface as the reflective film 166 on the flat plate 164. However, instead, the reflective film 168 may be partially removed so that the radiation window may be formed on the same surface as the reflective film 168 on the flat plate 164. As shown in various embodiments of the invention, the radiation window may be formed on either side of the plate 164.

Removing the reflective film is also possible by an etching process, but a mechanical removal process may be used and is cheaper. However, if the reflective film is mechanically removed, the plate 164 must be carefully treated to minimize damage to the plate 164. For example, if a portion of the plate 164 forming the radiation window is severely damaged, excessive losses due to scattering of incident light received at the plate 164 will occur.

Instead of forming the reflective film first and then removing it, the radiation window can be manufactured by first masking the portion of the flat plate 164 corresponding to the radiation window and protecting the portion from being covered by the reflective film.

As shown in FIG. 15C, a transparent adhesive 172 is applied to a portion where the reflective film 166 is removed from the reflective film 166 and the flat plate 164. The transparent adhesive 172 is also applied to the portion forming the radiation window in the flat plate 164, so that the possible light loss should be minimized.

As shown in FIG. 15D, a transparent protective plate 174 is attached over the transparent adhesive 172 to protect the reflective film 166 and the flat plate 164. Since the concave portion formed by applying the transparent adhesive 172 to remove the reflective film 166 is filled, the transparent protective plate 174 may be attached to the surface of the flat plate 164 in parallel.

Similarly, in order to protect the reflective film 168, an adhesive-not shown-can be applied to the surface of the reflective film 168, and a protective plate-not shown. If the reflective film 168 has a reflectance of nearly 100% and there is no radiation window on the same surface of the plate 164, the adhesive and protective plate need not be transparent.

In addition, an anti-reflection film 176 may be attached onto the transparent protective plate 174. For example, the transparent protective plate 174 and the radiation window 170 may be covered with the anti-reflection film 170.

According to this embodiment of the invention, the focal line is described as being on the opposite side of the surface from which incident light enters the flat plate. However, the focal line can be inside the plate, on the radiation window, or in front of the radiation window.

According to this embodiment of the present invention, light is reflected between two reflective films, one of which is approximately 100%. However, similar effects can be obtained when both reflecting films have a reflectance of less than 100%. For example, both reflecting films may have a reflectance of 95%. In this case, light is transmitted through both reflecting films, causing interference. As a result, light emission fluxes traveling in the direction determined by the wavelength are formed on both sides of the parallel plate on which the reflective film is formed. As such, various reflectances in various embodiments of the present invention may vary depending on the characteristics of the VIPA required.

According to this embodiment of the present invention, VIPA is described as being formed by a flat plate or two reflective surfaces parallel to each other. However, the flat or reflective surfaces do not necessarily have to be parallel.

According to the above embodiment of the present invention, it is possible to simultaneously split light including a plurality of wavelengths. Thus, the size of the receiver used in the wavelength multiplexing communication can be significantly reduced.

According to the above embodiment of the present invention, VIPA can simultaneously split wavelength-division multiplexed light into respective wavelengths. In addition, the dispersion angle is adjustable by the thickness t of the flat plate constituting the VIPA. As a result, the dispersion angle can be made large enough that the receiver can easily receive each divided signal. For example, in conventional diffraction gratings, fine concavo-convex surfaces are required to obtain large dispersion angles. However, it is very difficult to make fine and precise irregularities on the surface, which limits the size of the dispersion angle. In contrast, in the VIPA according to the embodiment of the present invention, it is only necessary to change the thickness of the plate in order to realize a relatively large dispersion angle.

VIPA according to this embodiment of the present invention makes a large dispersion angle compared to the conventional diffraction grating. Thus, the receiver using the VIPA according to the embodiment of the present invention can receive the optical signal exactly without failure, even in the case of wavelength multiplexing communication in which the high-level multiplexing process is implemented. Moreover, such a receiver is relatively simple in structure and inexpensive to manufacture.

In accordance with this embodiment of the present invention, VIPA maintains a constant phase difference between the lights interfering with each other using multiple reflections. As a result, the characteristic of VIPA is stabilized, and for this reason, the optical characteristic change due to polarization is reduced. In contrast, the optical properties of conventional diffraction gratings exhibit undesirable changes due to the polarization of incident light.

In addition, compared to the array waveguide grating, the VIPA according to the embodiment of the present invention is relatively simple in structure, stable in optical characteristics, and strong in resistance to changes in ambient conditions.

In this embodiment of the present invention, it is described that light emitting fluxes "spatially distinguishable" are formed from each other. "Spatially distinguishable" means that the luminescent fluxes can be distinguished from each other in space. For example, it is possible to distinguish spatially if multiple luminescent fluxes are collimated and progress in different directions or concentrated in different locations. However, these embodiments are not intended to limit the present invention as it is, and there are many other ways in which the light emission fluxes can be spatially distinguished from each other.

VIPA has a corresponding free spectral range that is determined by the thickness t between the reflective surfaces of VIPA, such as the thickness t between reflective surfaces 86, 88 in FIG. This free spectral region limits the wavelength band when VIPA is used as the wavelength divider, since the wavelength band is generally about the same as the free spectral region. For example, if the thickness t is 50 mu m, the wavelength band of VIPA is 16 nm, and the emission angle for each successive 16 nm wavelength band is repeated.

As such, incident light into VIPA may fall within a relatively wide wavelength range. This wavelength range will be divided into a number of wavelength bands determined by the free spectral region of the VIPA. For each wavelength band, the exit angle from VIPA is repeated.

VIPA with a wider wavelength band is often preferred. For example, thanks to recent technological advances, the bandwidth of optical amplifiers has increased dramatically. In order to effectively divide the light amplified by the optical amplifier, VIPA having a wide wavelength band or bandwidth would be preferable. To achieve this, the thickness t between the reflective surfaces of the VIPA must be thinner. However, the production of VIPA with a thickness t of less than 50 μm is not easy.

In order to solve the problem of the limited wavelength band of the VIPA, the use of the VIPA in combination with a wavelength splitter, also referred to as a demultiplexer, may provide an apparatus having a wide wavelength band.

16A and 16B illustrate a device in which VIPA is combined with a demultiplexer according to an embodiment of the present invention. 16A is a top view of the device, and FIG. 16B is a side view of the device.

As shown in FIGS. 16A and 16B, incident light, such as wavelength division multiplexed light, travels from the optical fiber 200 to the collimating lens 210. The collimating lens 210 collimates the incident light and provides the collimated lens 210 to the semi-cylindrical lens 220. Semi-cylindrical lens 220 directs light into line VIPA 230 (line-focuses).

VIPA generates outgoing light, such as light emitting flux, and provides it to a demultiplexer, such as diffraction grating 240. Diffraction grating 240 demultiplexes the light into a plurality of separate light or luminescent fluxes, which are concentrated in focal plane 260 by focus lens 250.

In general, VIPA 230 has a relatively high resolution within a narrow wavelength range. For example, FIG. 17A is a graph showing wavelength versus emission angle of VIPA. As shown in FIG. 17A, VIPA has a number of repeated wavelength bands determined by the free spectral region of VIPA. In general, the bandwidth of each wavelength band 280 is approximately equal to the free spectral region.

As shown in Fig. 17A, the wavelengths [lambda] 1, [lambda] 2, [lambda] 3, [lambda] 4, and [lambda] 5 are each dispersed at the same exit angle [theta] from VIPA. Accordingly, VIPA will disperse the emitted light having wavelength components corresponding to the wavelengths λ 1, λ 2, λ 3, λ 4, and λ 5 at the emission angle θ.

In contrast, FIG. 17B is a graph showing the wavelength versus emission angle of the diffraction grating. As shown in FIG. 17B, the diffraction grating has a wide wavelength band 290 that includes wavelengths λ 1, λ 2, λ 3, λ 4, and λ 5. The diffraction grating will disperse the wavelengths [lambda] 1, [lambda] 2, [lambda] 3, [lambda] 4, and [lambda] 5 into emission angles [theta] 1, [theta] 2, [theta] 3, [theta] 4 and [theta] 5, respectively.

It can be understood from FIGS. 17A and 17B that VIPA makes it possible to emit relatively adjacent wavelengths at significantly different exit angles within a wavelength band, such as wavelength band 280. As such, VIPA has a relatively high resolution, but this is possible within a narrow wavelength band. In contrast, diffraction gratings allow wavelengths to be separated over a wide bandwidth, but the exit angles are relatively close. Thus, the diffraction grating has a relatively low resolution, but this is possible at wide bandwidths.

16A and 16B can now be readily understood with reference to the resolution of VIPA 230 and diffraction grating 240. More specifically, as shown in FIGS. 16A and 16B, incident light is initially demultiplexed by a relatively high resolution VIPA 230 and then demultiplexed by a relatively low resolution diffraction grating 240. do.

18 is a diagram illustrating operation of a VIPA-diffraction device, in accordance with an embodiment of the present invention. As shown in FIG. 18, VIPA 230 receives incident light 295 having wavelengths λ 1, λ 2, λ 3, λ 4, λ 5, λ 6, λ 7, λ 8, λ 9, λ 10, λ 11, and λ 12. In response, VIPA 230 generates a number of light emitting fluxes, or outgoing lights 300, 310, 320, 330, and 340, which propagate from VIPA 230. The outgoing light 300 includes wavelengths λ 1, λ 6, and λ 11. The outgoing light 310 includes wavelengths lambda 2, lambda 7, and lambda 12. The outgoing light 320 includes wavelengths λ 3 and λ 8. The outgoing light 330 includes wavelengths λ 4 and λ 9. The outgoing light 340 includes wavelengths λ 5 and λ 10.

The diffraction grating 240 receives the outgoing light 300, 310, 320, 330, and 340, and demultiplexes each outgoing light into separate lights corresponding to the wavelengths included in the outgoing light, respectively. For example, the diffraction grating 240 demultiplexes the output light 300 into three lights having wavelengths λ 1, λ 6, and λ 11, respectively.

If the VIPA 230 scatters the outgoing light in a dispersion direction that is not parallel to the dispersion direction in which the diffraction grating 240 scatters the separated light, a relatively large number of densities Accurate demultiplexing of wavelength division multiplexed light having wavelength components.

For example, FIG. 18 shows a grid 350 in which points 1 through 12 are arranged in a grid pattern. Points 1 to 12 mark the ends of each optical fiber. If the dispersion direction of the VIPA 230 is substantially orthogonal to the dispersion direction of the diffraction grating 240, the separated light generated by the diffraction grating 240 may be received by the optical fibers arranged in a grid pattern. By such a configuration, it is possible to accurately demultiplex the wavelength division multiplexed light having a relatively large number of dense wavelength components.

This is not intended to limit the dispersion direction of the VIPA 230 to a direction perpendicular to the dispersion direction of the diffraction grating 240. For example, the dispersion direction only needs to be "not parallel". Furthermore, the present invention is not intended to be limited by the relationship between the dispersion directions. Thus, in some applications, it may be suitable for the dispersion directions to be parallel to each other.

It should be understood that both the VIPA and the diffraction grating emit light at an exit angle along the direction of dispersion. Thus, for example, VIPA 230 generates a plurality of outgoing lights that are each dispersed from VIPA at different exit angles. However, the emitted light is distributed along the same dispersion direction. In FIG. 18, the dispersion directions of VIPA 230 and diffraction grating 240 are preferably both fairly linear. For example, in FIG. 18, the dispersion direction of the VIPA 230 may be vertical with respect to the drawing, and the diffraction direction of the diffraction grating 240 may be horizontal with respect to the drawing. In this case, the dispersion directions will be perpendicular to each other.

The apparatus shown in FIG. 18 allows incident light belonging to a wide wavelength band to be demultiplexed with high accuracy and high resolution. For example, if the VIPA 230 demultiplexes 20 wavelengths with 0.8 nm spacing in the 16 nm wavelength band, and the diffraction grating 240 demultiplexes 5 wavelengths in the interval of each VIPA wavelength band. It is possible to demultiplex 100 wavelengths with an interval of 0.8 nm within a total bandwidth of 80 nm.

In this embodiment of the present invention, the diffraction grating 240 was used as a demultiplexer. However, this is not intended to limit the invention to the use of diffraction gratings. Any other suitable demultiplexer may be used instead. For example, a multilayer interference film can be used.

The apparatus according to this embodiment of the invention comprises a VIPA and a demultiplexer-for example a diffraction grating. VIPA receives incident light having a wavelength within the continuous wavelength range. In response, the corresponding outgoing light propagates from the VIPA. The exit angle is dispersed from the VIPA at different exit angles for each wavelength along a nearly linear dispersion direction. The scattered outgoing light also includes a number of different wavelength components. The demultiplexer demultiplexes the emitted light into a plurality of separate lights, each corresponding to a plurality of different wavelength components of the emitted light. The plurality of separated lights is distributed at different exit angles for each separated light along a nearly linear dispersion direction by the demultiplexer. The dispersion direction of VIPA is not parallel to the dispersion direction of the demultiplexer and is preferably vertical. Lenses that focus multiple separated lights on the focal plane may be attached such that each separated light is focused on a point on the focal plane that is different from the other separated light.

Incident light is typically wavelength division multiplexed light comprising two or more different wavelengths of light. VIPA then forms outgoing light for each of the incident lights. Each output light is spatially distinguishable from other output light, and each output light includes a number of different wavelength components. In this case, the demultiplexer demultiplexes each outgoing light into a plurality of separate lights, each corresponding to a plurality of different wavelength components of the outgoing light. Thereafter, a lens may be attached to focus the separated light from the demultiplexer on the focal plane. If the dispersion direction of the VIPA is nearly perpendicular to the dispersion direction of the demultiplexer, then each separated light is focused on a point on the focal plane different from the other separated light, so that different points can form a grid pattern on the focal plane. There will be.

An apparatus according to an embodiment of the present invention as illustrated in FIG. 18 demultiplexes incident light including a plurality of lights having different wavelengths. The apparatus includes first and second demultiplexers. For example, in FIG. 18, VIPA 230 acts as a first demultiplexer and diffraction grating 240 acts as a second demultiplexer. The first demultiplexer demultiplexes the incident light into a plurality of output lights respectively corresponding to the plurality of lights included in the incident light. The first demultiplexer distributes a plurality of outgoing lights at different outgoing angles for each outgoing light along a substantially linear dispersion direction. And, each of the emitted light includes a plurality of wavelength components. The second demultiplexer demultiplexes each outgoing light into a plurality of separate lights, each corresponding to a plurality of wavelength components included in the outgoing light. The second demultiplexer distributes the plurality of separated lights at different exit angles for each of the separated lights along a nearly linear dispersion direction. The dispersion direction of the second demultiplexer is not parallel to the dispersion direction of the first demultiplexer and is preferably perpendicular to each other. It is not intended to limit the first and second demultiplexers to VIPA and diffraction gratings. Instead, any suitable demultiplexer or wavelength divider can be used.

In general, VIPA is an angular dispersive component that receives light and has a passage area for emitting light. Through the pass region, VIPA receives incident light having respective wavelengths within the continuous wavelength range. VIPA causes multiple reflections of incident light, causing self-interference to form exiting light. The emitted light proceeds from the VIPA and can be spatially distinguished from the emitted light formed by the incident light having any other wavelength within the continuous wavelength range.

Various lenses are disclosed. For example, the use of collimating lens 210, semi-cylindrical lens 220, and focus lens 250 is disclosed in FIG. 16A. However, it is not intended to limit the present invention to the use of any particular type of lens. Instead, other types of lenses or devices can be used to achieve the proper effect.

The term "multiple" is used in this description to mean "more than one." Thus, a plurality of lights means "more than one" light. For example, two lights would be multiple lights.

VIPA according to an embodiment of the present invention can simultaneously split light including a plurality of wavelengths. Thus, the size of the receiver used in the wavelength division multiplexing system can be significantly reduced.

VIPA according to an embodiment of the present invention makes a large dispersion angle compared to the conventional diffraction grating. Thus, a receiver using VIPA according to an embodiment of the present invention can correctly receive an optical signal without failure even in the case of wavelength multiplexed communication in which high-level multiplexing processing is implemented. Moreover, such a receiver is relatively simple in structure and inexpensive to manufacture.

Combining VIPA according to an embodiment of the present invention with other demultiplexers allows incident light to be demultiplexed over a wide wavelength band with high accuracy and high resolution.

As the VIPA according to the embodiment of the present invention adjusts the distance between the reflective film or the reflective surface of the VIPA, the phase difference of the reflected light between the reflective film or the reflective surface may move by a predetermined amount, and thus the resistance to excellent ambient conditions ( environmental resistance). Moreover, the VIPA according to the embodiment of the present invention only slightly changes the optical properties depending on the polarization.

Although several preferred embodiments have been shown and described, it will be understood by those skilled in the art that modifications can be made in the above embodiments without departing from the spirit and the spirit of the invention, which fall within the scope and equivalency of the claims.

1 shows a conventional filter using a multilayer interference film.

FIG. 2 shows a conventional Fabry-Perot interferometer. FIG.

3 shows a conventional Michelson interferometer.

4 shows a conventional diffraction grating;

FIG. 5 illustrates a conventional array waveguide grating for splitting wavelength division multiplexed light. FIG.

FIG. 6 illustrates a Virtually Imaged Phased Array (VIPA), in accordance with an embodiment of the present invention. FIG.

FIG. 7 shows a cross section along line VII-VII of VIPA shown in FIG. 6, in accordance with an embodiment of the invention. FIG.

8 illustrates interference between reflected light caused by VIPA, in accordance with an embodiment of the present invention.

FIG. 9 shows a cross section along line VII-VII of VIPA shown in FIG. 6 to illustrate the structure of the light flux, according to an embodiment of the invention. FIG.

FIG. 10 shows a cross section along line VII-VII of VIPA shown in FIG. 6 to illustrate the characteristics of VIPA for determining the tilt angle of incident light, according to an embodiment of the invention;

11 illustrates VIPA used with a receiver, in accordance with an embodiment of the present invention.

12 illustrates a VIPA for use with a receiver, in accordance with a further embodiment of the present invention.

13 illustrates VIPA, according to another embodiment of the present invention.

FIG. 14 illustrates a waveguide type VIPA, in accordance with an embodiment of the present invention. FIG.

15A, 15B, 15C, and 15D illustrate a method of making VIPA in accordance with an embodiment of the present invention.

16A and 16B are plan and side views of an apparatus incorporating a demultiplexer, such as a diffraction grating, in VIPA, in accordance with an embodiment of the invention.

FIG. 17A is a graph showing wavelength versus emission angle of VIPA, in accordance with an embodiment of the present invention. FIG.

FIG. 17B is a graph showing wavelength versus emission angle of a diffraction grating, in accordance with an embodiment of the present invention. FIG.

18 shows an example of operation of a VIPA-diffraction device, in accordance with an embodiment of the invention.

<Explanation of symbols for the main parts of the drawings>

230: VIPA

240: diffraction grating

250: focus lens

350: grid

Claims (28)

Virtually Imaged Phased Array (VIPA) for receiving incident light, wherein the VIPA generates corresponding outgoing light propagating therefrom and the outgoing light comprises a plurality of different wavelength components; and And a demultiplexer for demultiplexing the outgoing light into a plurality of separate lights respectively corresponding to a plurality of different wavelength components included in the outgoing light. The method of claim 1, The VIPA distributes the emitted light along a linear dispersion direction, The demultiplexer distributes the separated light along a linear dispersion direction, Said dispersion direction of said VIPA is not parallel to said dispersion direction of said demultiplexer. 3. The apparatus of claim 2, wherein said dispersion direction of said VIPA is perpendicular to said dispersion direction of said demultiplexer. The method of claim 1, The incident light is within a wavelength band divided into a plurality of wavelength bands determined by the free spectral range of the VIPA, In each wavelength band, the VIPA has a higher resolution than the demultiplexer. The method of claim 1, i) the incident light is in a continuous wavelength range, ii) as the wavelength of the incident light changes over the continuous wavelength range,     ① The VIPA scatters the emitted light at different output angles for each wavelength along a linear dispersion direction,     The demultiplexer is adapted to produce the plurality of separated lights at different exit angles for each of the separated lights along a linear dispersion direction, wherein the dispersion direction of the demultiplexer is not parallel to the dispersion direction of the VIPA. Dispersing device. 6. The apparatus of claim 5 wherein the direction of dispersion of the VIPA is perpendicular to the direction of dispersion of the demultiplexer. The method of claim 1, i) the VIPA has a free spectral region, ii) the wavelength of the incident light is within a wavelength range divided into a plurality of wavelength bands determined by the free spectral region of the VIPA, iii) in each wavelength band, as the wavelength of the incident light changes within the wavelength band,     ① The VIPA scatters the emitted light at different emission angles for each wavelength along a linear dispersion direction,     (2) the demultiplexer receives the plurality of separated lights at different exit angles for each separated light along a linear dispersion direction wherein the dispersion direction of the demultiplexer is not parallel to the dispersion direction of the VIPA. Dispersing device. The apparatus of claim 1, wherein the demultiplexer is a diffraction grating. 3. The apparatus of claim 2, wherein the demultiplexer is a diffraction grating. The method of claim 1, The VIPA is an angular dispersive component having a pass area for receiving light and emitting light, The VIPA receives the incident light having respective wavelengths within the continuous wavelength range through the pass region and causes multiple reflection of the incident light, thereby generating self-interference, thereby 10. An apparatus for forming an outgoing light traveling from said VIPA that is spatially distinguishable from said outgoing light formed for incident light having any other wavelength. The lens of claim 2, further comprising a lens for focusing the plurality of separated lights on a focal plane. Each of the plurality of separated lights is focused at a point on the focal plane that is different from other separated lights. The method of claim 1, The incident light is composed of two or more lights each having a different wavelength, the VIPA forms a respective outgoing light for each light of the incident light, each outgoing light is spatially distinguishable from other outgoing light, Each emitted light contains a number of different wavelength components, And the demultiplexer demultiplexes each exiting light into a plurality of separate lights each corresponding to a plurality of different wavelength components of the exiting light. The method of claim 12, further comprising a lens for focusing the light separated from the demultiplexer on a focal plane. Wherein each separated light is focused at a point on the focal plane that is different from the other separated light, wherein the different points form a grid pattern on the focal plane. A virtually imaged phased array (VIPA) and a demultiplexer, The VIPA receives incident light having a wavelength within a continuous wavelength range to generate a corresponding outgoing light propagating out of the VIPA, the outgoing light having a different emission angle at each wavelength along a linear dispersion direction. Dispersed from VIPA, the scattered emitted light comprises a number of different wavelength components, The demultiplexer demultiplexes the outgoing light into a plurality of separate lights respectively corresponding to the plurality of different wavelength components included in the outgoing light, wherein the plurality of separated lights are each separated along a linear dispersion direction. And wherein the separated light is dispersed by the demultiplexer at different exit angles, and the dispersion direction of the VIPA is not parallel to the dispersion direction of the demultiplexer. The method of claim 14, further comprising a lens for focusing the plurality of separated lights on a focal plane. Wherein each separated light is focused at a point on the focal plane that is different from the other separated light. The method of claim 14, The incident light is composed of two or more lights each having a different wavelength, the VIPA forms a respective outgoing light for each light of the incident light, each outgoing light is spatially distinguishable from other outgoing light, Each emitted light contains a number of different wavelength components, And the demultiplexer demultiplexes each exiting light into a plurality of separate lights each corresponding to a plurality of different wavelength components of the exiting light. 17. The method of claim 16, further comprising a lens for focusing the separated light from the demultiplexer on a focal plane, Wherein each separated light is focused at a point on the focal plane that is different from other separated light, the different points forming a grid pattern on the focal plane. The method of claim 14, The VIPA is each dispersing element having a passing area for receiving light and emitting light, The VIPA receives the incident light having respective wavelengths within the continuous wavelength range through the passage region, causing multiple reflection of the incident light, thereby generating self-interference, thereby causing the continuous wavelength range. An apparatus for forming an exiting light proceeding from VIPA, spatially distinguishable from an exiting light formed by incident light having any other wavelength within. Each dispersion element, a demultiplexer, and a lens, Each of the dispersing elements has a pass-through area for receiving light and emitting light, and each of the dispersing elements receives incident light having respective wavelengths within a continuous wavelength range through the pass-through area, thereby allowing multiple reflections of the incident light. Generating self-interference, thereby generating outgoing light propagating from each of said dispersing elements, spatially distinguishable from outgoing light formed by incident light having any other wavelength within said continuous wavelength range, said outgoing light Is dispersed from each of the dispersing elements at different emission angles for each wavelength along a linear dispersion direction, and the scattered outgoing light includes a plurality of different wavelength components, The demultiplexer demultiplexes the emitted light into a plurality of separated lights corresponding to the plurality of different wavelength components respectively included in the emitted light, and the plurality of separated lights in a linear dispersion direction—the demultiplexer The dispersing direction of is not parallel to the dispersing direction of each dispersing element—dispersing at different exit angles for each separate light, The lens focuses the plurality of separated lights on a focal plane, wherein each separated light is focused at a point on the focal plane that is different from other separated light. 20. The apparatus of claim 19, wherein the demultiplexer is a diffraction grating. The method of claim 19, The incident light is composed of two or more lights, each of which is a different wavelength, wherein each dispersing element forms a respective outgoing light for each of the incident light, and each outgoing light is spatially distinguishable from the other outgoing light. Each of the emitted light includes a plurality of different wavelength components, The demultiplexer demultiplexes each outgoing light into a plurality of separate lights, each corresponding to a plurality of different wavelength components of the outgoing light, Wherein the lens focuses each separated light at a point on the focal plane that is different from the other separated light such that the different points form a grid pattern on the focal plane. In the apparatus for demultiplexing incident light including a plurality of lights having different wavelengths, A first demultiplexer and a second demultiplexer, The first demultiplexer demultiplexes the incident light into a plurality of output lights respectively corresponding to the plurality of lights included in the incident light, and the first demultiplexer is different for each output light along a linear dispersion direction. Emit a plurality of outgoing light at an exit angle, each outgoing light including a plurality of wavelength components, The second demultiplexer demultiplexes each outgoing light into a plurality of separate lights corresponding to the plurality of wavelength components included in the outgoing light, respectively, and the second demultiplexer decomposes each along a linear dispersion direction. And disperse the plurality of separated lights at different exit angles for each of the separated lights, wherein the direction of dispersion of the second demultiplexer is not parallel to the direction of dispersion of the first demultiplexer. 23. The apparatus of claim 22 wherein the direction of dispersion of the second demultiplexer is perpendicular to the direction of dispersion of the first demultiplexer. 23. The apparatus of claim 22, wherein the first demultiplexer is a Virtually Imaged Phased Array (VIPA). 23. The apparatus of claim 22, wherein the second demultiplexer is a diffraction grating. 25. The apparatus of claim 24, wherein the second demultiplexer is a diffraction grating. The method of claim 22, The first demultiplexer has a corresponding free spectral region, The incident light is within a wavelength range divided into a plurality of wavelength bands determined by the free spectral region of the first demultiplexer, In each wavelength band, the first demultiplexer has a higher resolution than the second demultiplexer. 23. The method of claim 22, further comprising a lens for focusing the separated light from the second demultiplexer on a focal plane, Wherein each separated light is focused at a point on the focal plane that is different from other separated light, the different points forming a grid pattern on the focal plane.