A wavelength-sensitive polarization device and an optical device made therefrom

Abstract

A wavelength-sensitive polarization device and an optical device made using the same, the wavelength-sensitive polarization device comprising a polarization beam splitter prism PBS having multiple faces and a filter element group arranged on at least one face of the polarization beam splitter prism, each filter element group consisting of a bandpass filter (110) and a quarter wave plate (120) arranged in sequence from the outside to the inside of the polarization beam splitter prism, the filter element group passing a polarized light signal of a specific wavelength and reflecting polarized light signals of other wavelengths except the specific wavelength, the specific wavelength light signal may have more than one wavelength; when the polarized light signals of other wavelengths pass through the PBS, one polarization component thereof is guided to the filter element group and then reflected back to the PBS by the filter element group, and the polarization state of the polarization component is rotated by 90 degrees. The device can realize the functions of multiple optical active / passive devices, such as wavelength division multiplexing function (K is greater than or equal to 2) of K-way signal channel transmission, optical switch function, wavelength division multiplexer and optical circulator, etc.

Description

Technical Field

[0001] The present application relates to the field of optical fiber communications, and in particular to a wavelength-sensitive polarization device and optical active / passive devices manufactured using its characteristics, such as a device with wavelength division multiplexing function (K is greater than or equal to 2) for transmitting K signal channels, a device with optical switch function, a wavelength division multiplexer and an optical circulator, etc. Background Art

[0002] With the rapid development of fiber-optic communications, the communication bandwidth is getting higher and higher. In the field of high-speed data communications, 100Gbps optical networks have begun to be commercialized on a large scale, and 200Gbps and 400Gbps optical communication systems have also begun to be gradually commercialized. While the speed and capacity of optical devices are being increased, higher and higher requirements are being placed on the miniaturization and reliability of optical devices. Summary of the invention

[0003] In view of the above defects and improvement needs of the prior art, an object of the present invention is to provide a wavelength-sensitive polarization device, which can be used as a basic component to easily assemble various optical active / passive devices.

[0004] Another object of the present invention is to provide various optical devices made of the above-mentioned wavelength-sensitive polarization device, such as optical devices with wavelength division multiplexing function for transmitting K signal channels, optical devices with wavelength selective switching function, small wavelength interval optical filters and optical circulators, etc.

[0005] An embodiment of the present invention provides a wavelength-sensitive polarization device, including a polarization beam splitter prism having multiple faces, at least one filter element group is arranged on at least one face of the polarization beam splitter prism, each filter element group is composed of a bandpass filter and a 1 / 4 wave plate arranged in sequence from the outside to the inside of the polarization beam splitter prism, the filter element group is used to pass a polarized light signal with a specific wavelength, and its bandpass filter transmits the polarized light signal with the specific wavelength and reflects polarized light signals of other wavelengths except the specific wavelength; at least one polarized light signal of other wavelength incident from other faces of the polarization beam splitter prism, a polarization component after passing through the polarization beam splitter prism is guided to the filter element group, and then reflected back to the polarization beam splitter prism by the filter element group, and the polarization state of the polarization component is rotated by 90 degrees.

[0006] Furthermore, the polarization beam splitter prism is provided with a 45-degree polarization beam splitting surface for transmitting a first polarization component of a light signal and reflecting a second polarization component whose polarization direction is perpendicular to the first polarization component, and the surface on which the filter element group is provided is parallel to the light passing surface of the bandpass filter and the quarter wave plate; the optical axis of the quarter wave plate and the first polarization component and the second polarization component all form an angle of 45 degrees; at least one polarized light signal of another wavelength incident from the other surface of the polarization beam splitter prism, one of the first polarization component or the second polarization component thereof is refracted by the polarization beam splitter prism PBS to the quarter wave plate, is reflected by the bandpass filter after passing through the quarter wave plate, and returns to the polarization beam splitter prism through the quarter wave plate again.

[0007] Furthermore, the polarization beam splitter prism includes at least one first incident surface and at least one first exit surface, and a first filter element group is arranged on the first incident surface.

[0008] Alternatively, the polarization beam splitter prism PBS includes at least one first incident surface and at least one first exit surface, and a first filter element group is arranged on the first exit surface.

[0009] Alternatively, the polarization splitter prism PBS includes at least one first incident surface and at least one first exit surface, a first filter element group for passing a first polarized light signal λ1 having a first wavelength is arranged on the first incident surface, and a second filter element group for passing a second polarized light signal λ2 having a second wavelength is arranged on the first exit surface.

[0010] Alternatively, the polarized light signal of a specific wavelength includes polarized light signals of more than one wavelength.

[0011] The wavelength-sensitive polarization device in this embodiment also includes a 1 / 4 wave plate arranged before the optical path of the first incident surface, so that the first polarized light signal with the first wavelength passes through the 1 / 4 wave plate and then passes through the bandpass filter and the 1 / 4 wave plate in sequence along the optical path direction of the first incident surface. After the polarization state is rotated 90 degrees, it enters the polarization splitter prism.

[0012] The wavelength-sensitive polarization device in this embodiment also includes a -1 / 4 wave plate arranged before the light path of the first incident surface, so that the first polarized light signal with the first wavelength passes through the -1 / 4 wave plate and then passes through the bandpass filter and the 1 / 4 wave plate in sequence along the light path direction of the first incident surface without changing the polarization state, and enters the polarization splitter prism.

[0013] A further improvement of the wavelength-sensitive polarization device in this embodiment is that the wavelength-sensitive polarization device is a regular N-gon, where N is an even number greater than 2; wherein there are M sides, and one filter element group is arranged on the surface of each side, and M is less than or equal to N.

[0014] A preferred embodiment of the present invention provides an optical device made using the above-mentioned wavelength-sensitive polarization device, wherein the first incident surface on which the first filter element group is set is configured to incident a first polarized light signal with a first wavelength; the optical device also includes a second incident surface, configured to incident a second polarized light signal with a second wavelength; and the polarization beam splitter prism is configured to combine the first polarized light signal and the second polarized light signal reflected by the bandpass filter into a light beam that arrives at the exit surface.

[0015] Another embodiment of the present invention provides another optical device made using the above-mentioned wavelength-sensitive polarization device, wherein at least a first polarized light signal having a first wavelength and a second polarized light signal having a second wavelength are incident from the incident surface, and the first exit surface provided with the first filter element group is configured to emit the first polarized light signal having the first wavelength; the optical device also includes a second exit surface provided with a second filter element group, which is configured to emit the second polarized light signal having the second wavelength.

[0016] Furthermore, the incident surface also receives a third polarized light signal λ3 having a third wavelength; the optical device further comprises a third output surface provided with a third filter element group, configured to output a third polarized light signal having a third wavelength.

[0017] Another embodiment of the present invention provides another optical device made using the above-mentioned wavelength-sensitive polarization device, wherein the optical device is a quadrilateral, and is provided with a first incident surface of a first filter element group, which is configured to incident a first polarized light signal with a first wavelength; the first output surface is opposite to the first incident surface, and outputs the first polarized light signal, and the first output surface simultaneously serves as a second incident surface to incident a third polarized light signal with a third wavelength; a second filter element group is also provided on a third surface adjacent to both the first output surface and the first incident surface, and the second filter element group only passes the second polarized light signal with a second wavelength and reflects polarized light signals of all other wavelengths; a fourth surface opposite to the third surface is a second output surface, and the polarization beam splitter is configured to fold the incident third polarized light signal back to the second output surface, and output the third polarized light signal.

[0018] Furthermore, a third filter element group is arranged on a fourth surface opposite to the third surface, which only passes a third polarized light signal having a third wavelength and reflects polarized light signals of all other wavelengths; the optical device also includes a second polarized light signal having a second wavelength incident on the second incident surface, which is configured to be refracted by the polarization splitter prism to be emitted from the third surface.

[0019] Another embodiment of the present invention provides another optical device made using the above-mentioned wavelength-sensitive polarization device, wherein the optical device is a quadrilateral, and is provided with a first incident surface of a first filter element group, which is configured to incident a first polarized light signal with a first wavelength; the first output surface is opposite to the first incident surface, and outputs the first polarized light signal, and simultaneously serves as a second incident surface to incident a third polarized light signal with a third wavelength; a reflector is provided on a third surface adjacent to both the first output surface and the first incident surface, reflecting the first polarized light signal and the third polarized light signal; a fourth surface opposite to the third surface is a second output surface, and the polarization splitter prism is configured to fold the incident third polarized light signal back to the second output surface, and output the third polarized light signal.

[0020] The wavelength-sensitive polarization device provided by the present invention significantly reduces the size of optical active / passive devices and improves reliability by setting the device to refract incident light signals and change their polarization states; miniaturization and high reliability of various optical active / passive devices are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0022] Figure 1a It is a schematic diagram of a structure and optical path of a wavelength-sensitive polarization device using only a set of 1 / 4 wave plates and a bandpass filter provided by a preferred embodiment of the present invention;

[0023] Figure 1b It is a schematic diagram of a structure and optical path of a wavelength-sensitive polarization device using only a set of 1 / 4 wave plates and bandpass filters provided by another embodiment of the present invention;

[0024] Figure 2a It is a schematic diagram of a structure and optical path of a wavelength-sensitive polarization device using two sets of 1 / 4 wave plates and a bandpass filter provided by a preferred embodiment of the present invention;

[0025] Figure 2b A schematic diagram of a structure and optical path of a wavelength-sensitive polarization device using two sets of 1 / 4 wave plates and a bandpass filter provided by another embodiment of the present invention;

[0026] Figure 2c It is a schematic diagram of a structure and optical path of a wavelength-sensitive polarization device using two sets of 1 / 4 wave plates and a bandpass filter provided by another embodiment of the present invention;

[0027] Figure 3 Schematic diagrams of several structures and optical paths of wavelength-sensitive polarization devices using three sets of quarter-wave plates and bandpass filters provided in an embodiment of the present invention;

[0028] Figure 4 This is another structural and optical path schematic diagram of a wavelength-sensitive polarization device using three groups of 1 / 4 wave plates and a bandpass filter provided in an embodiment of the present invention.

[0029] Figure 5 It is a schematic diagram of the structure and optical path of a wavelength-sensitive polarization device provided by another embodiment of the present invention using three groups of bandpass filters that can respectively pass two or more specific wavelength signal lights and reflect other wavelength signal lights.

[0030] Reference numerals

[0031] 100 Wavelength Sensitive Polarization Device

[0032] S1 First incident (exit) surface

[0033] S2 Second entrance (exit) surface

[0034] S3 The third incident (exit) surface

[0035] S4 Fourth incident (exit) surface

[0036] 110 First bandpass filter

[0037] 120 First 1 / 4 wave plate

[0038] 130 Polarization beam splitter PBS

[0039] 140 Second 1 / 4 wave plate

[0040] 150 Second bandpass filter

[0041] 160 Third 1 / 4 wave plate

[0042] 170 Third Bandpass Filter

[0043] 200 Filter Components Group

[0044] λ1 The first polarized light signal of the first wavelength

[0045] λ2 The second polarized light signal of the second wavelength

[0046] λ3 The third polarized light signal with the third wavelength DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0048] In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "upper", "lower", "top", "bottom" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and do not require that the present invention must be constructed and operated in a specific orientation. Therefore, they should not be understood as limitations on the present invention.

[0049] In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0050] Figure 1a The wavelength-sensitive polarization device 100 according to an embodiment of the present invention is shown, which is composed of a polarization beam splitter prism PBS with multiple faces, a quarter wave plate (or 1 / 4 wave plate) and a bandpass filter. The 1 / 4 wave plate and the bandpass filter can be located at any position of the top, bottom, left and right of the polarization beam splitter prism. The bandpass filter 110 and the 1 / 4 wave plate are sequentially arranged along the direction from the outside to the inside of the polarization beam splitter prism PBS. Such a pair of bandpass filters and 1 / 4 wave plates is called a filter element group 200.

[0051] exist Figure 1a In the preferred embodiment of the present invention shown, from bottom to top, there are a bandpass filter 110, a quarter wave plate 120 and a polarization beam splitter prism PBS130, which together constitute a wavelength-sensitive polarization device 100. The bandpass filter 110, the quarter wave plate 120 and the polarization beam splitter prism PBS130 are bonded together from bottom to top in the order of filter, quarter wave plate, polarization beam splitter prism PBS, and the bonding method can be glue bonding or the light-transmitting surface bonding method can be used. The lower surface of the polarization beam splitter prism 130 is parallel to the light-transmitting surfaces of the quarter wave plate 120 and the bandpass filter 110.

[0052] The function of the bandpass filter 110 is to transmit the λ optical signal with a specific wavelength and reflect the optical signal without the specific wavelength, or reflect the optical signal of other wavelengths except the specific wavelength. Without loss of generality, the function of the polarization beam splitter 130 is to transmit the p light and reflect the s light. In the present invention, the arrow symbol ↑ represents the p polarized light, and the ring or circle symbol · represents the s polarized light. The circularly polarized optical signal λ1I11 is incident from the incident surface below the wavelength sensitive polarization device 100, and is completely transmitted through the bandpass filter 100 and the 1 / 4 wave plate 120 to become I12. The polarization state of I12 is changed by the 1 / 4 wave plate 120 to become the linear polarized light of the first polarization component. Without loss of generality, it is assumed here that the linear polarization state of the first polarization component is the p polarization state, which can be transmitted through the 45-degree polarization beam splitting surface of the PBS 130. I12 becomes I13 after passing through the 45-degree polarization splitting plane of PBS 130. The polarization state of I13 remains unchanged, and is still in the p-polarization state, and is emitted from the exit surface above PBS 130. The optical signal λ2 incident in the direction orthogonal to λ1 is the linear polarization light of the second polarization component. Exemplarily, the linear polarization state of the second polarization component is the s-polarization state, which is called I21.

[0053] like Figure 1a As shown, I21 having a wavelength different from that of the polarized light signal λ1 enters PBS 130 from the incident surface on the right side of the polarization splitter prism PBS and is reflected by the 45-degree polarization splitting surface, enters the 1 / 4 wave plate 120 downward, and is reflected back to the 1 / 4 wave plate 120 by the bandpass filter 100 and passes through 120 to become I22; I22 rotates 90 degrees relative to the polarization state of I21, and the polarization state of I22 changes to linear polarized light of the first polarization component, that is, its polarization state is p polarization state, which can be transmitted through the 45-degree polarization splitting surface of PBS 130; I22 becomes I23 after passing through the 45-degree polarization splitting surface of PBS 130, and the polarization state of I23 remains unchanged, still in the p polarization state, and is combined with the λ1 signal into the same light at the exit surface above PBS 130, and the polarization state is consistent.

[0054] In this embodiment, the polarization beam splitter prism PBS is formed by gluing the hypotenuse of two high-precision right-angle prisms, and a polarization beam splitter film is coated on the hypotenuse. The angle of the hypotenuse is generally 45 degrees, so the bevel coated with the polarization beam splitter film is also called a 45-degree polarization beam splitter surface. The function of the polarization beam splitter prism PBS to vertically separate two different polarization states of light is also achieved by this gluing surface, that is, the 45-degree polarization beam splitter surface.

[0055] In addition, the optical axis of the 1 / 4 wave plate 120 forms an angle of 45 degrees with the first polarization component (P light) and the second polarization component (S light). This is because when the optical signal passes through the 1 / 4 wave plate 120, the light component of the optical signal parallel to the optical axis and the light component perpendicular to the optical axis will produce a phase difference of λ / 4, that is, 90°. When the linearly polarized light passes through the 1 / 4 wave plate, if the angle between the polarization direction and the direction of the optical axis of the wave plate is 45 degrees, then after passing through the wave plate, the polarized light becomes circularly polarized light. On the contrary, if the incident light is circularly polarized light, the outgoing light becomes linearly polarized light. Since the circularly polarized light signal has directionality, after the left-handed circularly polarized light and the right-handed circularly polarized light pass through the 1 / 4 wave plate, the outgoing linearly polarized light is orthogonal to each other. Generally, these two linearly polarized lights are artificially marked as P polarization component or S polarization component.

[0056] Therefore, the wavelength-sensitive polarization device provided in this embodiment mainly consists of a polarization beam splitter prism 130, a quarter wave plate 120 and a bandpass filter 110. One surface (S1) of the polarization beam splitter prism 130 is parallel to the light passing surfaces of the quarter wave plate 120 and the bandpass filter 110. The polarization beam splitter prism is used to split the incident non-polarized light into two beams of mutually perpendicular linear polarized light. The quarter wave plate 120 is configured to change the polarization state of the passing optical signal. The bandpass filter 110 is used to transmit the optical signal of a specific wavelength and reflect other optical signals except the specific wavelength.

[0057] Exemplarily, the wavelength-sensitive polarization device can be combined with another quarter-wave plate to form a structure of a first quarter-wave plate, a bandpass filter, a second quarter-wave plate, and a polarization beam splitter prism from left to right. Light signals of specific wavelengths can be selectively transmitted through the bandpass filter. The specific light signal is incident from the left side, passes through the first quarter-wave plate, the bandpass filter, and the second quarter-wave plate in sequence, and enters the polarization beam splitter prism after the polarization state is rotated 90 degrees. Similarly, light signals of non-specific wavelengths can also be incident on the polarization beam splitter prism from other directions, and are incident on the bandpass filter after reflection or transmission. Due to the selective reflection of the bandpass filter, the polarization state of the non-specific wavelength light signal is rotated 90 degrees and then reflected back to the polarization beam splitter prism.

[0058] Alternatively, the wavelength-sensitive polarization device can be combined with another -1 / 4 wave plate to form a structure of -1 / 4 wave plate, bandpass filter, 1 / 4 wave plate, and polarization beam splitter prism from left to right. The specific wavelength light signal can be selectively transmitted through the bandpass filter. The specific wavelength light signal is incident from the left side, passes through the -1 / 4 wave plate, bandpass filter, and 1 / 4 wave plate in sequence, and enters the polarization beam splitter prism without changing the polarization state. Similarly, the non-specific wavelength light signal can also be incident on the polarization beam splitter prism from other directions, and is incident on the bandpass filter after reflection or transmission. Due to the selective reflection of the bandpass filter, the polarization state of the non-specific wavelength light signal is rotated 90 degrees and then reflected back to the polarization beam splitter prism.

[0059] In addition, the function of the wavelength division multiplexer is to combine optical signals of different wavelengths into one optical signal. In order to clearly demonstrate the optical path of the λ1λ2 signal, the optical path of the λ2 signal is not drawn together with the optical path of the λ1 signal. However, when the λ1λ2 composite light beam transmits out of the PBS 130, they are actually combined into the same light path, and the situation of the subsequent λ3λ4 signal is the same.

[0060] The same structure can also be used to combine three signals. Figure 1b As shown in the example, the optical signal λ3 incident in a direction orthogonal to λ1 is a linearly polarized light of the third polarization component. Without loss of generality, it is assumed here that the linear polarization state of the third polarization component is an s polarization state, enters PBS 130, is reflected by the 45-degree polarization splitter surface, passes through PBS 130, and is combined with the λ1 and λ2 signals into the same light, completing the multiplexing of three optical signals of different wavelengths.

[0061] By combining a plurality of such wavelength-sensitive polarization devices 100 , a wavelength division multiplexing function for transmitting multiple (K) signal channels can be achieved (K is greater than or equal to 2).

[0062] In the above embodiment, the wavelength-sensitive polarization device includes only one filter element group 200. Since the polarization beam splitter prism PBS includes at least one incident surface and one exit surface, the filter element group can be arranged on the incident surface or on the exit surface. It can be understood that in other embodiments, the wavelength-sensitive polarization device can also be composed of one polarization beam splitter prism and multiple filter element groups, that is, two or more groups of quarter-wave plates and band-pass filters. The two or more groups of quarter-wave plates and band-pass filters can be located at adjacent positions or at opposite positions.

[0063] Figure 2a The preferred embodiment of the present invention in the figure shows a situation where two groups of quarter wave plates and band pass filters are adjacent, or an example of two adjacent filter element groups. As shown in the figure, from bottom to top are the first band pass filter 110, the first 1 / 4 wave plate 120 and the polarization beam splitter prism 130, and from right to left are the second band pass filter 140 and the second 1 / 4 wave plate 150 respectively located on the right side of the polarization beam splitter prism 130, 110, 120, 130, 140, 150 together constitute a wavelength sensitive polarization device 100'. The lower surface of the polarization beam splitter prism 130 is parallel to the light passing surfaces of the first 1 / 4 wave plate 120 and the first band pass filter 110, and the right surface of the polarization beam splitter prism 110 is parallel to the light passing surfaces of the second 1 / 4 wave plate 150 and the second band pass filter 140.

[0064] This embodiment is used to illustrate the situation when the wavelength-sensitive polarization device 100 corresponds to multiple wavelengths incident from a certain port at the same time. Without loss of generality, it is assumed that the function of the bandpass filter 110 is to transmit λ 1-N signal, and reflects at least λ 2-M and λ 3-L Here N, M, and L are all positive integers; for example, 1-N represents N signals with wavelengths near λ1. The function of the bandpass filter 140 is to transmit λ 3-L signal, and reflects at least λ 1-N and λ 2-M Wait for the signal.

[0065] Exemplarily, the polarization beam splitter prism 130 transmits s light and reflects p light. Although most of the coated polarization beam splitters transmit p light and reflect s light, some devices, such as a sub-wavelength metal grating made on a 45-degree polarization beam splitting plane, can also transmit s light and reflect p light.

[0066] S-polarized light signal group λ 2-M It is transmitted by the polarization splitter prism 130, enters the 1 / 4 wave plate 150, is reflected by the bandpass filter 140 and re-enters the 1 / 4 wave plate 150, and the polarization state is changed to p-polarized light and enters the PBS 130. It enters the 1 / 4 wave plate 120 after being reflected by the PBS 130, is reflected by the bandpass filter 110 and re-enters the 1 / 4 wave plate 120, becomes s-polarized light after transmission, and is transmitted out from the top by the PBS 130, maintaining the s-polarization state.

[0067] At the same time, the circularly polarized light λ incident from the right perpendicular to the light passing surface of the bandpass filter 140 3-L After the signal passes through the 1 / 4 wave plate 120, the polarization direction changes to the p polarization state, is reflected downward by the PBS 130 and enters the 1 / 4 wave plate 120, is reflected by the bandpass filter 110 and re-enters the 1 / 4 wave plate 120, becomes s polarized light after transmission, is transmitted from the top by the PBS 130, and λ 2-M Signal light overlap.

[0068] On the other hand, the circularly polarized light λ incident from below perpendicular to the light passing surface of the bandpass filter 110 1-N After the signal passes through the quarter wave plate 120, the polarization direction is changed to the s polarization state and is transmitted by the PBS 130. 3-L and 2-M The signal lights overlap, and the polarization states of the three groups of lights are completely consistent. Therefore, in this embodiment, the optical device made of the wavelength-sensitive polarization device 100 realizes the function of a wavelength division multiplexer.

[0069] exist Figure 2bIn the preferred embodiment of the present invention, two sets of quarter wave plates and band pass filters are shown opposite to each other. From bottom to top, there are a first band pass filter 110, a first quarter wave plate 120, a polarization beam splitter prism 130, a second quarter wave plate 150, and a second band pass filter 140. Here, 110, 120, 130, 140, and 150 together constitute a wavelength sensitive polarization device 100". The lower surface of the polarization beam splitter prism 130 is parallel to the first quarter wave plate 120 and the first band pass filter 110, and the upper surface of the polarization beam splitter prism 110 is parallel to the second quarter wave plate 150 and the second band pass filter 140.

[0070] Exemplarily, it is assumed that the polarization beam splitter prism 130 transmits p-light and reflects s-light.

[0071] S-polarized light signal group λ 2-M It is reflected downward by the polarization splitter prism 130, enters the 1 / 4 wave plate 120, is reflected by the bandpass filter 110 and re-enters the 1 / 4 wave plate 120, and its polarization state is changed to p-polarized light and enters the PBS 130. After transmitting through the PBS 130, it enters the 1 / 4 wave plate 150, is reflected by the bandpass filter 140 and re-enters the 1 / 4 wave plate 150, becomes s-polarized light after transmission, and is reflected by the PBS 130, maintaining the s-polarization state and the transmission direction unchanged.

[0072] At the same time, the circularly polarized light λ incident from the direction perpendicular to the light passing surface of the bandpass filter 110 1-N After the signal passes through the 1 / 4 wave plate 120, the polarization direction changes to the p polarization state, passes through the PBS 130, enters the 1 / 4 wave plate 150, is reflected by the bandpass filter 140, re-enters the 1 / 4 wave plate 150, becomes s polarized light after transmission, is reflected by the PBS 130, and λ 2-M Signal light overlap.

[0073] On the other hand, the circularly polarized light λ incident from a direction perpendicular to the light passing surface of the bandpass filter 140 3-L After the signal passes through the quarter wave plate 150, the polarization direction is changed to s polarization state and is reflected by the PBS 130, and λ 1-N and 2-M The signal lights overlap, and the polarization states of the three groups of lights are completely consistent. Therefore, this device realizes the function of a wavelength division multiplexer.

[0074] When the incident light λ1 and λ3 are incident from opposite positions, the wavelength-sensitive polarization device can also act as an optical circulator. Figure 2cAs shown, the optical signal λ1 incident from the incident surface S1 on the left side of the wavelength-sensitive polarization device 100 is circularly polarized light. The optical axis of the 1 / 4 wave plate 120 forms an angle of 45 degrees with the first polarization component and the second polarization component, and is configured to change the first polarization light signal λ1 from a left-handed (or right-handed) circularly polarized light signal to a linearly polarized light with a polarization state of the first polarization component (P); the bandpass filter 110 is used to transmit λ1 and at least reflect the λ3 signal; a bandpass filter 150 is provided on the upper side of the wavelength-sensitive polarization device 100, and its function is to at least reflect the λ1 and λ3 signals. After the optical signal λ1 passes through the 1 / 4 wave plate 120, the polarization state is rotated 90 degrees to change to the P polarization state, and is transmitted through the bandpass filter 110 and the PBS 130, and is emitted from the right exit surface S4 window opposite to the incident surface S1.

[0075] The random polarization light signal λ3 incident in the opposite direction to λ1 (i.e. incident from the right side S4 surface), its S polarization component enters PBS 130, is reflected upward by the 45-degree polarization splitter, enters 1 / 4 wave plate 140, is reflected back to 1 / 4 wave plate 140 by bandpass filter 150 again, and the polarization state is rotated 90 degrees to become P polarization state, transmits through PBS 130, and is emitted through S2 surface below wavelength sensitive polarization device 100; the P component of light signal λ3 transmits through the 45-degree polarization splitter surface and enters 1 / 4 wave plate 120, is reflected back to 1 / 4 wave plate by bandpass filter 110 again, and the polarization state is changed to S polarization light, propagates to the right and enters 130, is reflected downward by the 45-degree polarization splitter of 130, and is combined with the P polarization component of λ3 signal into the same light path, and is emitted from S2 surface together. In this way, the optical circulator function of light incident on S1 surface is emitted from S4 surface, and light incident on S4 surface is emitted from S2 surface is realized.

[0076] Alternatively, a reflector may be provided on the upper side of the wavelength-sensitive polarizer 100, for example, a reflector coated with a high-reflection film, as long as it can reflect the λ1 and λ3 signals. This can achieve the same effect as the bandpass filter 150, so that the optical device made of the wavelength-sensitive polarizer 100 can complete the function of an optical circulator.

[0077] The wavelength sensitive polarization device 100 may also be composed of a polarization beam splitter prism and three sets of 1 / 4 wave plates and band pass filters, which are located in adjacent positions, and two sets of 1 / 4 wave plates and band pass filters are located in opposite positions.

[0078] like Figure 3As shown, in a preferred embodiment of the present invention, the wavelength-sensitive polarization device 100 is composed of a polarization beam splitter (PBS) 130, quarter-wave plates 120, 140, 160, and band-pass filters 140, 150, 170. The function of the band-pass filter 110 is to transmit the λ1 signal and at least reflect the λ2 and λ3 signals. The function of the band-pass filter 150 is to transmit the λ2 signal and at least reflect the λ1 and λ3 signals. The function of the band-pass filter 170 is to transmit the λ3 signal and at least reflect the λ1 and λ2 signals. The random polarized light signal λ1 is incident from the left side S1 surface, and after transmitting through the bandpass filter 110 and the 1 / 4 wave plate 120, the P polarization component in λ1 is transmitted through the PBS 130, and the S polarization component is reflected downward by the 45-degree polarization splitter surface of 130, enters the 1 / 4 wave plate 160, and is reflected back to the 1 / 4 wave plate 160 by the bandpass filter 170 again, and the polarization state is changed to become P polarized light and propagates upward into the PBS 130. The P polarized light transmits through the polarization splitter surface and enters the 1 / 4 wave plate 140, and is reflected back to the 1 / 4 wave plate by the bandpass filter 150 again, and the polarization state is rotated 90 degrees to become S polarized light and propagates downward into the PBS 130, and is reflected to the right by the 45-degree polarization splitter surface of 130, and is combined with the P polarization component of the λ1 signal into the same light path, and is emitted from the S4 surface on the right side.

[0079] The random polarization light signal λ3 incident in the opposite direction to λ1 (i.e., incident from the right S4 surface), its S polarization component enters the PBS 130, is reflected upward by the 45-degree polarization splitter, enters the 1 / 4 wave plate 140, is reflected back to the 1 / 4 wave plate 140 by the bandpass filter 150 again, and the polarization state is changed to the P polarization state, is transmitted through the PBS 130, passes through the 1 / 4 wave plate 160 and the bandpass filter 170, and is emitted from the S2 surface below the wavelength sensitive polarization device 100; the P component of the optical signal λ3 transmits through the 45-degree polarization splitter surface and enters the 1 / 4 wave plate 120, is reflected back to the 1 / 4 wave plate by the bandpass filter 110 again, and the polarization state is rotated 90 degrees to become S polarized light, propagates to the right and enters 130, is reflected downward by the 45-degree polarization splitter of 130, and is combined with the P polarization component of the λ3 signal to form the same light path, and is emitted from the S2 surface below.

[0080] The random polarization light signal λ2 incident in the opposite direction to λ1 (same as λ3, incident from the right side S4 surface), its S polarization component enters PBS 130, is reflected upward by the 45-degree polarization splitter, enters 1 / 4 wave plate 140 and bandpass filter 150, and is emitted from the upper side S3 surface; the P component of the light signal λ2 transmits through the 45-degree polarization splitter surface and enters 1 / 4 wave plate 120, is reflected back to the 1 / 4 wave plate by bandpass filter 110 again, and the polarization state is changed to S polarization light, propagates to the right and enters 130, is reflected downward by the 45-degree polarization splitter of 130 and passes through 1 / 4 wave plate 160, is reflected back to 1 / 4 wave plate 160 by bandpass filter 170, and the polarization state is changed to P polarization state, transmits upward through PBS 130, passes through 1 / 4 wave plate 140 and bandpass filter 150, and is combined with the S polarization component of the λ2 signal into the same light, and is emitted from the upper side S3 surface together. In this way, the function of a small wavelength interval optical filter is achieved, in which the randomly polarized incident light on the S1 surface is emitted from the S4 surface, the λ3 signal light incident on the S4 surface is emitted from the S2 surface, and the λ2 signal light incident on the S4 surface is emitted from the upper S3 surface.

[0081] like Figure 4 As shown, in a preferred embodiment of the present invention, the wavelength-sensitive polarization device 100 is composed of a polarization beam splitter prism (PBS) 130, quarter-wave plates 120, 140, 160, and bandpass filters 110, 150, 170. The function of the bandpass filter 110 is to transmit λ 1-N signal, and reflects at least λ 2-M and λ 3-L The function of the bandpass filter 150 is to transmit λ 2-M signal, and reflects at least λ 1-N and λ 3-L The function of the bandpass filter 170 is to transmit λ 3-L signal, and reflects at least λ 1-N and λ 2-M Signal.

[0082] Random polarization signal λ 1-N The incident light is from the right side S4 surface, and after passing through the bandpass filter 110 and the 1 / 4 wave plate 120, λ 1-N The P polarized component in the beam is transmitted through PBS 130, and the S polarized component is reflected upward by the 45-degree polarization splitter of 130, enters the 1 / 4 wave plate 140, and is reflected back to the 1 / 4 wave plate by the bandpass filter 150 again, and the polarization state is changed to become P polarized light and propagates downward into 130. The P polarized light passes through the polarization splitter and enters the 1 / 4 wave plate 160, and is reflected back to the 1 / 4 wave plate by the bandpass filter 170 again, and the polarization state is changed to become S polarized light and propagates upward into 130, and is reflected to the left by the 45-degree polarization splitter of 130, and λ 1-NThe P polarization components of the signal are combined into the same light path and emitted from the left S1 surface.

[0083] With λ 1-N Random polarized light signals incident from the same direction λ 3-L (i.e., incident from the right S4 surface), its S polarization component enters PBS 130, is reflected upward by the 45-degree polarization splitter, enters 1 / 4 wave plate 140, is reflected back to 1 / 4 wave plate 140 by bandpass filter 150, and the polarization state is changed to P polarization state, transmits through PBS 130, passes through 1 / 4 wave plate 160 and bandpass filter 170, and is emitted from the lower S2 surface; optical signal λ 3-L The P component of the λ3 signal is transmitted through the 45-degree polarization splitter surface and enters the 1 / 4 wave plate 120, and is reflected back to the 1 / 4 wave plate by the bandpass filter 110 again. The polarization state is changed to S polarized light, which propagates to the right and enters 130, and is reflected downward by the 45-degree polarization splitter surface of 130, and is combined with the P polarization component of the λ3 signal into the same light, which is emitted from the S2 surface below.

[0084] With λ 1-N Random polarized light signals incident from the same direction λ 2-M (i.e. incident from the S4 surface), its S polarization component enters the PBS 130, is reflected upward by the 45-degree polarization splitter, enters the 1 / 4 wave plate 140 and the bandpass filter 150, and exits from the S3 surface; the optical signal λ 2-M The P component of the light is transmitted through the 45-degree polarization splitter surface into the 1 / 4 wave plate 120, and is reflected back to the 1 / 4 wave plate by the bandpass filter 110 again. The polarization state is changed to S polarized light and propagates to the right into 130. After being reflected downward by the 45-degree polarization splitter surface of 130 and passing through the 1 / 4 wave plate 160, it is reflected back to the 1 / 4 wave plate 160 by the bandpass filter 170. The polarization state is changed to P polarization state, and is transmitted upward through the PBS 130, passing through the 1 / 4 wave plate 140 and the bandpass filter 150, and λ 2-M The S polarization components of the signal are combined into the same light path and emitted from the upper S3 surface.

[0085] In this way, the wavelength-sensitive polarization device 100 and three groups of filter elements are used to realize the function of a wavelength division multiplexer in which optical signals of different wavelengths of randomly polarized incident light on the S4 surface are emitted from the S1 surface, the S2 surface, and the S3 surface respectively. As is known to all, the function of a wavelength division multiplexer is to decompose optical signals of different wavelengths in the same signal. 1-N λ 2-M The optical path of the signal does not 2-M Signal optical path and λ 1-N The optical paths of the signals are drawn together, but when they enter the PBS130, they are actually the same path of light combined together. 3-L The same is true for signals.

[0086] In an alternative embodiment of the present invention, the polarization splitter prism PBS includes at least one first incident surface S1 and at least one first exit surface S4, a first filter element group for passing a first polarized light signal λ1 having a first wavelength is arranged on the first incident surface S1, and a second filter element group for passing a second polarized light signal λ2 having a second wavelength is arranged on the first exit surface S4.

[0087] In an alternative embodiment, the bandpass filter involved in the present invention can be configured to pass signal lights of two or more specific wavelengths and reflect signal lights of other wavelengths. Figure 5 According to a preferred embodiment of the present invention, a wavelength-sensitive polarization device 100 is shown, which is composed of a polarization beam splitter (PBS) 130, a quarter wave plate 120, 140, 160, and a bandpass filter 110, 150, 170. The function of the bandpass filter 110 is to transmit signals with wavelengths of 1270 nm and 1330 nm, and at least reflect signals with wavelengths of 1290 nm, 1310 nm, 1350 nm, and 1370 nm. The function of the bandpass filter 150 is to transmit signals with wavelengths of 1290 nm and 1350 nm, and at least reflect signals with wavelengths of 1270 nm, 1330 nm, 1310 nm, and 1370 nm. The function of the bandpass filter 170 is to transmit signals with wavelengths of 1310 nm and 1370 nm, and at least reflect signals with wavelengths of 1270 nm, 1330 nm, 1290 nm, and 1350 nm.

[0088] like Figure 5 As shown, randomly polarized optical signals with wavelengths of 1270nm and 1330nm are incident from the right side S4 surface, and after being transmitted through the bandpass filter 110 and the 1 / 4 wave plate 120, the P polarization components of the 1270nm and 1330nm wavelengths are transmitted through the PBS 130, and the S polarization components are reflected upward by the 45-degree polarization splitter surface of 130, enter the 1 / 4 wave plate 140, and are reflected back to the 1 / 4 wave plate by the bandpass filter 150 again, and the polarization state is changed to become P polarized light and propagate downward into 130, and the P polarized light is transmitted through the polarization splitter surface and enters the 1 / 4 wave plate 160, and is reflected back to the 1 / 4 wave plate by the bandpass filter 170 again, and the polarization state is changed to become S polarized light and propagate upward into 130, and is reflected to the left by the 45-degree polarization splitter surface of 130, and is combined with the P polarization components of the signals with wavelengths of 1270nm and 1330nm to form the same light path, and are emitted from the left side S1 surface together.

[0089] The randomly polarized optical signals with wavelengths of 1310nm and 1370nm incident in the same direction as 1270nm and 1330nm (i.e., incident from the right S4 surface), have their S polarization components enter the PBS 130, are reflected upward by the 45-degree polarization splitter, enter the 1 / 4 wave plate 140, and are reflected back to the 1 / 4 wave plate 140 by the bandpass filter 150 again, and the polarization state is changed to the P polarization state, which is transmitted through the PBS 130, and then passes through the 1 / 4 wave plate 160 and the bandpass filter 170, and is emitted from the lower S2 surface; the P components of the optical signals 1310nm and 1370nm are transmitted through the 45 The 45-degree polarization splitter surface enters the 1 / 4 wave plate 120, and is reflected back to the 1 / 4 wave plate by the bandpass filter 110 again. The polarization state changes to S-polarized light, propagates to the right and enters 130, is reflected downward by the 45-degree polarization splitter surface of 130, and is combined with the P-polarized component of the 1310nm and 1370nm wavelength optical signals into the same light, which is emitted from the S2 surface below.

[0090] The randomly polarized optical signals with wavelengths of 1290nm and 1350nm incident in the same direction as the wavelengths of 1270nm and 1330nm (i.e., incident from the S4 surface), have their S polarization components entering the PBS 130, reflected upward by the 45-degree polarization splitter surface, entering the 1 / 4 wave plate 140 and the bandpass filter 150, and exiting from the S3 surface; the P components of the optical signals with wavelengths of 1290nm and 1350 transmit through the 45-degree polarization splitter surface and enter the 1 / 4 wave plate 120, and are reflected back to the 1 / 4 wave plate by the bandpass filter 110 again, and the polarization state is changed to S polarized light, propagating to the right into 130, and are reflected downward by the 45-degree polarization splitter surface of 130 through the 1 / 4 wave plate 160, and are reflected back to the 1 / 4 wave plate 160 by the bandpass filter 170, and the polarization state is changed to P polarization state, and are transmitted upward through the PBS 130, through the 1 / 4 wave plate 140 and the bandpass filter 150, is combined with the S polarization components of the 1290nm and 1350nm wavelength optical signals into the same light path, and is emitted from the upper side S3 surface together.

[0091] In this way, the wavelength-sensitive polarization device 100 and three groups of filter elements are used to realize the function of a wavelength division multiplexer in which optical signals of different wavelengths of the randomly polarized incident light on the S4 surface are emitted from the S1 surface, the S2 surface and the S3 surface respectively. As is well known, the function of a wavelength division multiplexer is to separate optical signals of different wavelengths in the same signal. In order to clearly demonstrate the optical paths of the 1270nm, 1290nm, 1330nm and 1350nm wavelength signals, the optical paths of the 1290nm and 1350nm wavelength signals and the optical paths of the 1270nm and 1330nm wavelength signals are not drawn together, but when incident into the PBS 130, they are actually combined into the same light path, and the situation of the subsequent 1310nm and 1370nm wavelength signals is the same.

[0092] In another alternative embodiment of the present invention, a wavelength-sensitive polarization device consisting of a polarization beam splitter prism, one or more quarter-wave plates and a band-pass filter can also be used to make an optical switch (not shown in the figure). In a preferred embodiment, the optical switch can also be composed of a polarization beam splitter prism and four groups of quarter-wave plates and a band-pass filter, that is, a filter element group is arranged on each surface of the polarization beam splitter prism.

[0093] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved. In addition, it is obvious that the word "comprising" does not exclude other units or steps, and the singular does not exclude the plural. Multiple units or devices stated in the device claim can also be implemented by one unit or device through software or hardware. The words first, second, etc. are used to indicate names, and do not indicate any particular order.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An optical device made of a wavelength-sensitive polarization device, characterized in that: A wavelength-sensitive polarization device (100) comprises a polarization beam splitter (PBS) having a plurality of faces, at least one filter element group (200) being arranged on at least one face of the polarization beam splitter (PBS), each filter element group (200) being composed of a bandpass filter (110) and a quarter wave plate (120) being arranged in sequence from the outside to the inside of the polarization beam splitter (PBS), the filter element group (200) being used to pass a polarized light signal having a specific wavelength, the bandpass filter (110) transmitting the polarized light signal having the specific wavelength and reflecting polarized light signals of other wavelengths except the specific wavelength; the polarized light signal of the specific wavelength comprises polarized light signals of more than one wavelength; At least one polarized light signal of another wavelength incident from another surface of the polarization beam splitter prism (PBS) has a polarization component guided to the filter element group (200) after passing through the polarization beam splitter prism (PBS), and then reflected back to the polarization beam splitter prism (PBS) by the filter element group (200), and the polarization state of the polarization component is rotated by 90 degrees; The polarization beam splitter (PBS) comprises at least one first incident surface (S1) and at least one first exit surface (S4), a first filter element group being arranged on the first exit surface (S4); at least a first polarized light signal λ1 having a first wavelength and a second polarized light signal λ2 having a second wavelength are incident from the incident surface, the first exit surface on which the first filter element group is arranged is configured to emit the first polarized light signal λ1 having the first wavelength; the optical device further comprises a second exit surface on which a second filter element group is arranged, configured to emit the second polarized light signal λ2 having the second wavelength; the incident surface also receives a third polarized light signal λ3 having a third wavelength; the optical device further comprises a third exit surface on which a third filter element group is arranged, configured to emit the third polarized light signal λ3 having the third wavelength; Alternatively, the polarization beam splitter (PBS) comprises at least one first incident surface (S1) and at least one first exit surface (S4), and a first filter element group is arranged on the first incident surface (S1); the optical device is a quadrilateral, and is provided with a first incident surface (S1) of the first filter element group, which is configured to incident a first polarized light signal λ1 having a first wavelength; the first exit surface is opposite to the first incident surface (S1) and emits the first polarized light signal λ1, and the first exit surface simultaneously serves as a second incident surface (S2) to incident a third polarized light signal λ3 having a third wavelength; a second filter element group is also arranged on a third surface adjacent to both the first exit surface and the first incident surface (S1), The second filter element group only passes the second polarized light signal λ2 with the second wavelength, and reflects polarized light signals of all other wavelengths; the fourth surface opposite to the third surface is the second exit surface, and the polarization beam splitter prism PBS is configured to fold the incident third polarized light signal λ3 back to the second exit surface, and emit the third polarized light signal λ3; a third filter element group is arranged on the fourth surface opposite to the third surface, which only passes the third polarized light signal λ3 with the third wavelength, and reflects polarized light signals of all other wavelengths; the optical device also includes a second polarized light signal λ2 with the second wavelength incident on the second incident surface (S2), which is configured to be folded back by the polarization beam splitter prism PBS to the third surface for emission; Alternatively, the polarization beam splitter (PBS) comprises at least one first incident surface (S1) and at least one first exit surface (S4), and a first filter element group is arranged on the first incident surface (S1); the optical device is a quadrilateral, and is provided with a first incident surface (S1) of the first filter element group, which is configured to incident a first polarized light signal λ1 having a first wavelength; the first exit surface is opposite to the first incident surface (S1), and emits the first polarized light signal λ1, and simultaneously serves as a second incident surface (S2) to incident a third polarized light signal λ3 having a third wavelength; a reflector is arranged on a third surface adjacent to both the first exit surface and the first incident surface (S1), and reflects the first polarized light signal λ1 and the third polarized light signal λ3; a fourth surface opposite to the third surface is a second exit surface, and the polarization beam splitter PBS is configured to fold the incident third polarized light signal λ3 back to the second exit surface, and emit the third polarized light signal λ3.

2. An optical device made of a wavelength-sensitive polarization device as claimed in claim 1, characterized in that: The polarization beam splitting prism PBS (130) is provided with a 45-degree polarization beam splitting surface for transmitting a first polarization component (P) of a light signal and reflecting a second polarization component (S) whose polarization direction is perpendicular to the first polarization component, and the surface of the filter element group (200) is arranged to be parallel to the light passing surfaces of the bandpass filter (110) and the quarter wave plate (120); The optical axis of the quarter wave plate (120) forms an angle of 45 degrees with the first polarization component (P) and the second polarization component (S); At least one polarized light signal of another wavelength incident from the other surface of the polarization beam splitter prism PBS has one of its first polarization component (P) or second polarization component (S) refracted by the polarization beam splitter prism PBS to the quarter wave plate (120), reflected by the band pass filter (110) after passing through the quarter wave plate (120), and returned to the polarization beam splitter prism (PBS) through the quarter wave plate (120) again.

3. An optical device made of a wavelength-sensitive polarization device according to any one of claims 1 to 2, characterized in that: The polarization beam splitter prism PBS includes at least one first incident surface (S1) and at least one first exit surface (S4), a first filter element group for passing a first polarized light signal λ1 having a first wavelength is arranged on the first incident surface (S1), and a second filter element group for passing a second polarized light signal λ2 having a second wavelength is arranged on the first exit surface (S4).

4. An optical device made of a wavelength-sensitive polarization device according to any one of claims 1 to 2, characterized in that: The method further comprises arranging a quarter wave plate before the optical path of the first incident surface (S1), so that the first polarized light signal λ1 having the first wavelength passes through the quarter wave plate and then sequentially passes through a band pass filter (110) and a quarter wave plate (120) along the optical path direction of the first incident surface (S1), and after the polarization state is rotated by 90 degrees, enters a polarization beam splitter prism PBS (130).

5. An optical device made of a wavelength-sensitive polarization device according to any one of claims 1 to 2, characterized in that: The method further comprises arranging a -1 / 4 wave plate before the optical path of the first incident surface (S1), so that the first polarized light signal λ1 having the first wavelength passes through the -1 / 4 wave plate and then sequentially passes through a bandpass filter (110) and a 1 / 4 wave plate (120) along the optical path direction of the first incident surface (S1), with the polarization state unchanged, and enters a polarization splitting prism PBS (130).

6. An optical device made of a wavelength-sensitive polarization device according to any one of claims 1 to 2, characterized in that: The wavelength-sensitive polarization device (100) is a regular N-gon, where N is an even number greater than 2; There are M edges, and a filter element group is arranged on the surface of each edge, where M is less than or equal to N.

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