阅读说明：本技术 用于交叉极化信号传输的无线电单元和无线电链路收发器 (Radio unit and radio link transceiver for cross-polarized signal transmission ) 是由 J·桑德伯格 于 2018-08-21 设计创作，主要内容包括：本公开涉及适于交叉极化信号传输(230)的无线电单元(420、420A、420B),其包括布置成分别向以及从外部源传输交叉极化信号以用于交叉极化干扰抵消XPIC的光传送接口(430、430A、430B)和光接收接口(440、440A、440B)。光传送接口(430、430A、430B)和光接收接口(440、440A、440B)以距接口的对称线(450)相等的距离(D)来布置,并且处于垂直于对称线(450)的平面(451)中。当将无线电单元(420、420A、420B)围绕对称线(450)旋转180度时,旋转后的光传送接口与旋转前的光接收接口对齐,并且旋转后的光接收接口与旋转前的光传送接口对齐。(The present disclosure relates to a radio unit (420, 420A, 420B) adapted for cross-polarized signal transmission (230), comprising an optical transmitting interface (430, 430A, 430B) and an optical receiving interface (440, 440A, 440B) arranged to transmit cross-polarized signals to and from, respectively, an external source for cross-polarized interference cancellation, XPIC. The light transmitting interface (430, 430A, 430B) and the light receiving interface (440, 440A, 440B) are arranged at equal distances (D) from a line of symmetry (450) of the interfaces and in a plane (451) perpendicular to the line of symmetry (450). When the radio unit (420, 420A, 420B) is rotated 180 degrees around the symmetry line (450), the rotated optical transmit interface is aligned with the optical receive interface before rotation, and the rotated optical receive interface is aligned with the optical transmit interface before rotation.)

1. A radio unit (420, 420A, 420B) adapted for cross-polarized signal transmission (230), comprising an optical transmit interface (430, 430A, 430B) and an optical receive interface (440, 440A, 440B), wherein said optical transmit interface (430, 430A, 430B) and said optical receive interface (440, 440A, 440B) are arranged to transmit cross-polarized signals to and from external sources, respectively, for cross-polarized interference cancellation, XPIC, wherein said optical transmit interface (430, 430A, 430B) and said optical receive interface (440, 440A, 440B) are arranged at equal distances (D) from a line of symmetry (450) of the interfaces and in a plane (451) perpendicular to said line of symmetry (450) such that when said radio unit (420, 420A, 420B) is rotated 180 degrees around said line of symmetry (450), said optical transmit interface after rotation is aligned with said optical receive interface before rotation, and the rotated light receiving interface is aligned with the light transmitting interface before rotation.

2. The radio unit (420, 420A, 420B) of claim 1, wherein the light transmitting interface (430, 430A, 430B) comprises a light emitting diode, LED, and the light receiving interface (440, 440A, 440B) comprises a photodetector.

3. The radio unit (420, 420A, 420B) of claim 1, wherein the optical transmit interface (430, 430A, 430B) comprises a laser transmitter and the optical receive interface (440, 440A, 440B) comprises a laser detector.

4. A radio unit (420, 420A, 420B) according to any preceding claim, wherein the optical transmit interface (430, 430A, 430B) is a differential transmit interface comprising a first (431) and a second (432) optical transmitter, wherein the optical receive interface (440, 440A, 440B) is a differential receive interface comprising a first (441) and a second (442) optical detector.

5. A radio unit (420, 420A, 420B) according to any preceding claim, wherein the optical transmission interface (430, 430A, 430B, 810) comprises a lens arrangement (860) configured to focus the emitted optical signal (851, 852).

6. A radio unit (420, 420A, 420B) according to any preceding claim, wherein the light receiving interface (440, 440A, 440B, 820) comprises a lens arrangement (870) configured to focus the received light signal (851, 852).

7. The radio unit (420, 420A, 420B) according to any preceding claim, comprising an antenna interface (410) arranged on the symmetry line (450).

8. A radio unit (420, 420A, 420B) according to any preceding claim, wherein the cross-polarized signal comprises an analog signal.

9. A radio unit (420, 420A, 420B) according to any preceding claim, wherein the cross-polarized signal comprises a digital signal.

10. A radio unit (420, 420A, 420B) according to any preceding claim, wherein the cross-polarized signal comprises a control signal.

11. A radio unit (420, 420A, 420B) according to any preceding claim, wherein any of the optical transmit interface (430, 430A, 430B, 810) and/or the optical receive interface (440, 440A, 440B, 820) comprises an optical gasket (830) arranged to optically seal connections involving the optical interface.

12. A radio link transceiver (500) comprising a first radio unit (420, 420A) according to any of claims 1-11, a corresponding second radio unit (420, 420B) according to any of claims 1-11, and a mounting structure (510), wherein the mounting structure comprises a light guiding arrangement (540) arranged to guide light between a light transmitting interface (430, 430A, 430B) and a respective light receiving interface (440, 440A, 440B).

13. The radio link transceiver (500) of claim 12, wherein the light directing arrangement (540) comprises tooling holes configured to align with an optical transmit interface (530A) of the first radio unit (420A) on a first side and with a corresponding optical receive interface (530B) of the second radio unit (420B) on a second side.

14. The radio link transceiver (500) of claim 12 or 13, wherein the light guiding arrangement (540) comprises a transparent element configured to guide light from an optical transmit interface (530A) of the first radio unit (420A) on a first side to a respective optical receive interface (530B) of the second radio unit (420B) on a second side.

15. The radio link transceiver (500) of claim 14, wherein the transparent element is a transparent rod arranged to be glued into a machined hole of the mounting structure (510).

16. The radio link transceiver (500) of claim 12 or 13, wherein the light guiding arrangement (540) comprises a tube with a reflective or light absorbing inner coating.

17. The radio link transceiver (500) of any of claims 12-16, wherein the mounting structure (510) comprises an orthogonal mode converter, OMT, arranged to interface with respective antenna interfaces (410) of the first and second radio units and to interface with an antenna unit (110).

18. A radio link transceiver (700) comprising a first radio unit (720A), a second radio unit (720B), each radio unit (720A, 720B) comprising an optical transmit interface (730A, 730B) and an optical receive interface (740A, 740B), wherein each optical transmit interface (730A, 730B) and each optical receive interface (740A, 740B) are arranged to transmit cross-polarized signals for cross-polarized interference cancellation, XPIC, wherein the optical transmit interface (730A) and the optical receive interface (740A) on the first radio unit (720A) are arranged according to a mirror image of the optical receive interface (740B) and the optical transmit interface (730B) on the second radio unit (720B), respectively, such that when the first radio unit (720A) is mirrored with the optical interface (730B, B) facing the second radio unit (720B), 740B) When the optical interfaces (730A, 740A) of the first radio unit (720A) are aligned, the optical transmit interface (730A) of the first radio unit (720A) is aligned with the optical receive interface (740B) of the second radio unit (720B), and the optical receive interface (740A) of the first radio unit (720A) is aligned with the optical transmit interface (730B) of the second radio unit (720B).

19. A radio link transceiver (700) according to claim 18, comprising a mounting structure (710) comprising a light guiding arrangement (750) arranged to guide light between the optical transmit interface (730A, 730B) and the respective optical receive interface (740A, 740B).

20. A method in a radio unit (420, 420A, 420B), wherein the method comprises:

arranging (S101) an optical transmit interface (430, 430A, 430B) and an optical receive interface (440, 440A, 440B) at equal distances (D) from a line of symmetry (450) of the interfaces and in a plane (451) perpendicular to the line of symmetry (450) such that when the radio unit (420, 420A, 420B) is rotated 180 degrees around the line of symmetry (450), the optical transmit interface after rotation is aligned with the optical receive interface before rotation and the optical receive interface after rotation is aligned with the optical transmit interface before rotation; and

using (S102) the optical transmitting interface (430, 430A, 430B) and the optical receiving interface (440, 440A, 440B) is for transmitting cross-polarized signals to and from external sources, respectively, for cross-polarized interference cancellation, XPIC.

21. A method in a radio link transceiver (500), wherein the method comprises:

aligning (S201) a first radio unit (420A) with a corresponding second radio unit (420B), such that an optical interface (430A, 430B; 440A, 440B) according to claim 20 is aligned between the radio units (420A, 420B), such that the first optical transmit interface 430A is aligned with the second optical receive interface 440B, and the first optical receive interface 440A is aligned with the second optical transmit interface 430B; and

an optical connection (230) is established using (S202) the intermediate mounting structure (510).

22. A method in a radio link transceiver (700), wherein the method comprises:

arranging (S301) an optical transmit interface (730A) and an optical receive interface (740A) on a first radio unit (720A) according to a mirror image of an optical receive interface (740B) and an optical transmit interface (730B) on a second radio unit (720B), respectively, such that when the first radio unit (720A) is aligned with an optical interface (730A, 740A) facing the optical interface (730B, 740B) of the second radio unit (720B), the optical transmit interface (730A) of the first radio unit (720A) is aligned with the optical receive interface (740B) of the second radio unit (720B), and the optical receive interface (740A) of the first radio unit (720A) is aligned with the optical transmit interface (730B) of the second radio unit (720B); and

-using (S302) each optical transmit interface (730A, 730B) and each optical receive interface (740A, 740B) for transmitting cross-polarized signals between said radio units (720A, 720B) for cross-polarized interference cancellation, XPIC.

23. The method of claim 22, wherein the method comprises using a light guiding arrangement (750) of the mounting structure (710) to guide light between the light transmitting interface (730A, 730B) and the respective light receiving interface (740A, 740B).

Technical Field

The present disclosure relates to point-to-point radio communication links, such as microwave radio links. Methods and arrangements for transmitting radio signals between first and second radio units are disclosed herein.

Background

There is a dual polarized radio link transmitting two signal streams, one for each polarization, using cross-polarization signals for cross-polarization interference cancellation (XPIC). When two streams are received, there is residual mutual interference that should be properly suppressed. Two received polarizations (typically linear horizontal H and vertical V) are each routed to a corresponding transceiver, one for H polarization and one for V polarization.

In order to implement XPIC, there must be a connection between one transceiver for H-polarization and one for V-polarization, so that in a previously well-known manner, the transceiver for H-polarization can compensate for interference of V-polarization and so that the transceiver for V-polarization can compensate for interference of H-polarization.

The connection between the two transceivers is typically accomplished by means of a multi-signal cable (e.g., a cable having 4 pairs of twisted pairs and a relatively small connector, about 60cm long). Such cables are difficult to connect and disconnect if the transceiver needs to be changed or installed, particularly if the work is performed at mast height. Cable-based connections also suffer from losses at high frequencies; signals transmitted between transceivers for XPIC may have a bandwidth greater than 1 GHz.

Therefore, it is desirable to have a more reliable connection for signals transmitted between transceivers, which are intended for XPICs.

Disclosure of Invention

It is an object of the present disclosure to provide a more reliable connection for signals transmitted between transceivers, which are intended for XPICs.

This object is achieved by means of a radio unit adapted for cross-polarized signal transmission comprising an optical transmission interface arranged to transmit cross-polarized signals to and from, respectively, an external source for cross-polarized interference cancellation (XPIC). The optical transmission interface and the optical reception interface are arranged at equal distances from a line of symmetry of the interface and in a plane perpendicular to the line of symmetry. In this way, when the radio unit is rotated 180 degrees around the symmetry line, the rotated optical transmit interface is aligned with the optical receive interface before rotation, and the rotated optical receive interface is aligned with the optical transmit interface before rotation.

This enables the radio units to be aligned with corresponding radio units so that optical communication can be established between the radio units when the radio units are mounted facing each other. A radio unit having optical communication adapted for cross-polarized signals for XPIC eliminates the need for external expensive cabling and associated EMC (electromagnetic compatibility) problems due to cabling, makes installation easier, and simplifies servicing of installed equipment.

According to some aspects, the light transmitting interface comprises a Light Emitting Diode (LED) and the light receiving interface comprises a photo detector.

Alternatively, the optical transmission interface comprises a laser transmitter and the optical reception interface comprises a laser detector.

In this way, optical communication is achieved by means of an optical interface using well-known and inexpensive components.

According to some aspects, the optical transmission interface is a differential transmission interface comprising first and second optical transmitters. Correspondingly, the light receiving interface is a differential receiving interface comprising a first and a second light detector.

According to some aspects, the optical transmission interface comprises a lens arrangement (lens arrangement) configured to focus the emitted optical signal.

According to some aspects, the light receiving interface comprises a lens arrangement configured to focus the received light signal.

The lens arrangement provides more reliable optical communication. The lens arrangement may also improve optical communication performance due to the increased received signal quality.

According to some aspects, the cross-polarized signals comprise analog signals and/or digital signals. According to some aspects, the cross-polarization signal comprises a control signal.

This allows many types of communication.

According to some aspects, any of the optical transmit interface and the optical receive interface comprises an optical gasket (gasket) arranged to optically seal connections involving the optical interface.

This provides a secure seal. The spacer may also shield interfering light sources, thereby improving the optical communication conditions on the interface.

The object is also achieved by means of a radio link transceiver comprising a first radio unit according to the above and a corresponding second radio unit according to the above and a mounting structure. The mounting structure comprises a light guiding arrangement arranged to guide light between the light transmitting interface and the respective light receiving interface.

In this way, reliable optical communication can be established between the radio units. By enabling optical communication of cross-polarized signals for XPIC, externally expensive cabling and associated EMC issues arising from the cabling are eliminated, making installation easier, enabling easy maintenance of installed equipment.

According to some aspects, the light directing arrangement comprises a machined hole configured to align with the light transmitting interface of the first radio unit on the first side and with the corresponding light receiving interface of the second radio unit on the second side.

Machining the holes can facilitate cost-effective implementation of the disclosed techniques.

According to some aspects, the light directing arrangement comprises a transparent element configured to direct light from the light transmitting interface of the first radio unit on the first side to the respective light receiving interface of the second radio unit on the second side.

The transparent element may act as a guide to direct the optical signal from the transmitter to the receiver without significant loss.

According to some aspects, the transparent element is a rod arranged to be glued into a machined hole of the mounting structure.

According to some aspects, the light directing arrangement comprises a tube having a reflective inner coating or a light absorbing inner coating.

The above arrangement ensures reliable and efficient optical communication via the light guiding arrangement.

According to some aspects, the mounting structure comprises an orthogonal mode transducer omt (orthogonal mode transducer) arranged to interface with respective antenna interfaces of the first and second radio units and to interface with the antenna units.

In this way, two orthogonal polarizations can be combined/separated.

The object is also achieved by means of a radio link transceiver comprising a first radio unit and a second radio unit, wherein each radio unit comprises an optical transmit interface and an optical receive interface. Each optical transmit interface and each optical receive interface is arranged to transmit cross-polarized signals for cross-polarization interference cancellation (XPIC). The optical transmission interface and the optical reception interface on the first radio unit are arranged according to a mirror image of the optical reception interface and the optical transmission interface on the second radio unit, respectively. This means that when the first radio unit is aligned with the optical interface facing the optical interface of the second radio unit, the optical transmission interface of the first radio unit is aligned with the optical reception interface of the second radio unit, and the optical reception interface of the first radio unit is aligned with the optical transmission interface of the second radio unit.

In this way, optical communication can be established between radio units in a versatile manner. By enabling optical communication of cross-polarized signals for XPIC, externally expensive cabling and associated EMC issues arising from the cabling are eliminated, installation is made easier, and easy maintenance of installed equipment is achieved.

According to some aspects, a radio link transceiver comprises a mounting structure comprising an optical directing arrangement arranged to direct light between an optical transmit interface and a respective optical receive interface.

In this way, reliable optical communication can be established between the radio units.

Also disclosed herein are methods corresponding to the devices according to the above, wherein the methods show advantages corresponding to the advantages already described with respect to the corresponding above devices.

Drawings

The present disclosure will now be described in more detail with reference to the accompanying drawings, in which:

figure 1 shows a schematic diagram of a point-to-point radio communication link;

FIG. 2 schematically illustrates an XPIC radio transceiver system;

FIG. 3 illustrates an XPIC radio transceiver system according to the prior art;

figure 4 shows an example radio unit for cross-polarized signal transmission;

FIGS. 5-7 schematically illustrate XPIC radio transceiver systems;

FIG. 8A illustrates an example optical gasket;

8B-8C schematically illustrate a lens arrangement; and

fig. 9-11 are flow charts illustrating methods.

Detailed Description

Aspects of the present disclosure will now be described more fully with reference to the accompanying drawings. The various devices and methods disclosed herein may, however, be embodied in many different forms and should not be construed as limited to the aspects set forth herein. Like numbers refer to like elements throughout.

The terminology used herein is for the purpose of describing aspects of the disclosure only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Referring to fig. 1, there is a first point-to-point radio link 100, which in turn comprises a first antenna 110A, a first radio link transceiver 101A, a second antenna 110B and a second radio link transceiver 101B. The radio link 100 is adapted to communicate via two linear polarizations; a horizontally polarized H-POL and a vertically polarized V-POL, wherein the polarizations H-POL, V-POL are mutually orthogonal or at least substantially orthogonal.

Hereinafter, the antenna 110 and the corresponding radio link transceiver 101 will be described with reference to fig. 2. The radio-link transceiver 101 comprises a first radio unit 220A intended for horizontally polarized H-POL and a second radio unit 220B intended for vertically polarized V-POL. The radio units 220A, 220B comprise respective first and second transceiver interfaces 210A, 210B, which are connected to respective first and second equalizers 240A, 240B. The first transceiver interface 210A comprised in the first radio unit 220A is furthermore connected to a second cross-polarization interference cancellation (XPIC) unit 250B comprised in the second radio unit 220B, and the second transceiver interface 210B comprised in the second radio unit 220B is further connected to a first XPIC unit 250A comprised in the first transceiver interface 210A, which connections are adapted for cross-polarization signal transmission 230 between the radio units 220A, 220B.

In the first radio unit 220A, the outputs of the first XPIC unit 250A and the first equalizer 240A are connected to a first summing device 260A, which first summing device 260A is in turn connected to a first detector unit 270A. Correspondingly, in the second radio unit 220B, the outputs of the second XPIC unit 250B and the second equalizer 240B are connected to a second summing device 260B, which second summing device 260B is in turn connected to a second detector unit 270B.

Cross-polarization interference cancellation is achieved by adapting the equalizer and XPIC units such that interference cancellation occurs in the summing means 260A, 260B. Signal processing for cross-polarization interference cancellation is known and will not be discussed in detail here.

As initially described, cross-polarized signal transmission 230 has previously been constructed from multiple signal cables, which are associated with a number of drawbacks. In fig. 3, a prior art radio link transceiver 300 is shown having an antenna interface 310 and two radio units 320A, 320B connected by a multi-signal cable 330.

Referring to fig. 4, there is a radio unit 420 adapted for cross-polarized signal transmission 230 comprising an antenna interface 410, for example consisting of a waveguide signal interface. The radio unit 420 also includes additional interfaces such as a power interface and one or more data service interfaces disposed on the bottom surface 460 of the radio unit 420.

According to the present disclosure, radio unit 420 comprises an optical transmit interface 430 and an optical receive interface 440, wherein optical transmit interface 430 and optical receive interface 440 are arranged to transmit 230 the cross-polarized signal to and from an external source, respectively, for XPIC. The optical transmit interface 430 and the optical receive interface 440 are arranged at equal distance D from the symmetry line 450 of the interfaces and in a plane 451 perpendicular to the symmetry line 450 such that when the radio unit 420 is rotated 180 degrees around the symmetry line 450, the rotated optical transmit interface 430 is aligned with the optical receive interface 440 before rotation and the rotated optical receive interface is aligned with the optical transmit interface before rotation. This means that when two radio units are mounted facing each other, the optical transmit interface 430 and the optical receive interface 440 are adapted to be paired with corresponding optical interfaces of the opposing further radio unit, as will be described later for the radio link transceiver.

The antenna interface 410 may be arranged, for example, on the symmetry line 450.

According to some aspects, the light transmitting interface 430 comprises a Light Emitting Diode (LED) and the light receiving interface 440 comprises a photodetector.

According to some aspects, alternatively, the light transmitting interface 430 comprises a laser emitter and the light receiving interface 440 comprises a laser detector.

According to some aspects, as shown in fig. 4, the optical transmit interface 430 is a differential transmit interface comprising a first 431 and a second 432 optical transmitters, wherein further the optical receive interface 440 is a differential receive interface comprising a first 441 and a second 442 optical detector.

With reference to fig. 5 and 6, the present disclosure also relates to a radio link transceiver 500 comprising a first radio unit 420A of the same type as the above described radio unit 420 and a corresponding second radio unit 420B of the same kind as the above described radio unit 420 as well. This means that the radio units 420A, 420B comprise a corresponding first and second optical transmit interface 430A, 430B corresponding to the optical transmit interface 430 described above and a first and second optical receive interface 440A, 440B corresponding to the optical receive interface 440 described above.

The radio link transceiver 500 further comprises a mounting structure 510, wherein the mounting structure comprises a light guiding arrangement 540 arranged to guide light between the optical transmit interfaces 430A, 430B and the respective optical receive interfaces 440A, 440B. This means that the first optical transmission interface 430A is adapted to be paired with the second optical reception interface 440B, and the first optical reception interface 440A is adapted to be paired with the second optical transmission interface 430B. In this context, the term pairing means that the optical connection 230 is established and the optical connection 230 is realized via the optical guiding arrangement 540.

According to some aspects, the light directing arrangement 540 comprises a machined hole configured to align with the light transmitting interface 530A of the first radio unit 420A on the first side and with the corresponding light receiving interface 530B of the second radio unit 420B on the second side.

According to some other aspects, the light directing arrangement 540 comprises a transparent element configured to direct light from the light transmitting interface 530A of the first radio unit 420A on the first side to the respective light receiving interface 530B of the second radio unit 420B on the second side.

The light transmitting interfaces 530A, 530B may, for example, comprise a contact surface adapted to contact the mounting structure 510 and a light directing portion.

According to some aspects, the transparent element is a transparent rod arranged to be glued or otherwise assembled into a machined hole in the mounting structure 510.

According to some aspects, the light directing arrangement 540 comprises a tube having a reflective inner coating or a light absorbing inner coating.

According to some aspects, the mounting structure 510 includes an Orthogonal Mode Transducer (OMT) arranged to interface with the respective antenna interfaces 410 of the first and second radio units and to interface with the antenna unit 110.

A more general and asymmetric approach is disclosed in fig. 7, where a radio link transceiver 700 comprises a first radio unit 720A and a second radio unit 720B, where each radio unit 720A, 720B comprises an optical transmit interface 730A, 730B and an optical receive interface 740A, 740B. The first radio unit 720A includes a first optical transmit interface 730A and a first optical receive interface 740A, while the second radio unit 720B includes a second optical transmit interface 730B and a second optical receive interface 740B.

Each optical transmit interface 730A, 730B and each optical receive interface 740A, 740B is arranged to transmit cross-polarized signals for cross-polarization interference cancellation (XPIC). The first optical transmission interface 730A and the first optical reception interface 740A are arranged on the first radio unit 720A according to the mirror image of the second optical reception interface 740B and the optical transmission interface 730B on the second radio unit 720B, respectively.

In this way, when the first radio unit 720A is aligned with the first optical interface 730A, 740A facing the second optical interface 730B, 740B of the second radio unit 720B, the first optical transmit interface 730A of the first radio unit 720A is aligned with the second optical receive interface 740B of the second radio unit 720B. Correspondingly, the first optical receiving interface 740A of the first radio unit 720A is aligned with the second optical transmitting interface 730B of the second radio unit 720B.

According to some aspects, the radio link transceiver 700 comprises a mounting structure 710 comprising a light guiding arrangement 750 arranged to guide light between the optical transmit interfaces 730A, 730B and the respective optical receive interfaces 740A, 740B.

According to some aspects, the optical interfaces 730A, 730B; 740A, 740B have an optical interface 430A, 430B with that previously described; 440A, 440B are of the same or similar design; and, according to some aspects, the mounting structure 710 has the same or similar design as the mounting structure 510 previously described.

According to some aspects, the optical transport interface 430; 430A, 430B; 730A, 740A, 810 and a light receiving interface 440; 440A, 440B; 740A, 740B, 820 comprises an optical gasket 830 arranged to optically seal connections involving optical interfaces. One example of such a shim is shown in fig. 8A. The optical gasket 830 covers the connection between the optical transmission interface and the optical reception interface, thereby sealing the connection. The encapsulation may provide protection from other light sources that may interfere with optical communication 840, and according to some aspects, may also provide protection from unwanted moisture and dirt. The gasket may for example be a rubber gasket, such as an o-ring gasket.

Referring to fig. 8B and 8C, according to some aspects, the optical transmission interface 810 comprises a lens arrangement 860 configured to focus optical signals 851, 852 emitted from an optical source 850 comprised in the optical transmission arrangement. The light receiving interface 820 may also include a lens arrangement 870 configured to focus the received light signals 851, 852. It is to be appreciated that any of the interfaces may include a lens, i.e., a lens may be disposed on only the transmit side as shown in fig. 8B, only the receive side as shown in fig. 8C, or on both the transmit and receive sides (not shown).

Referring to fig. 9, the present disclosure also relates to a method in a radio unit 420, 420A, 420B, wherein the method comprises:

arranging S101 the optical transmit interfaces 430, 430A, 430B and the optical receive interfaces 440, 440A, 440B at equal distances D from the line of symmetry 450 of the interfaces and in a plane 451 perpendicular to the line of symmetry 450 such that when the radio units 420, 420A, 420B are rotated 180 degrees around the line of symmetry 450, the rotated optical transmit interfaces are aligned with the optical receive interfaces before rotation and the rotated optical receive interfaces are aligned with the optical transmit interfaces before rotation; and using S102 the optical transmit interfaces 430, 430A, 430B and the optical receive interfaces 440, 440A, 440B is for transmitting cross-polarized signals to and from external sources, respectively, for cross-polarized interference cancellation, XPIC.

Referring to fig. 10, the present disclosure also relates to a method in a radio link transceiver 500, wherein the method comprises:

aligning S201 a first radio unit 420A with a corresponding second radio unit 420B such that the optical interface 430A, 430B according to claim 20; 440A, 440B are aligned between the radio units 420A, 420B such that the first optical transmit interface 430A is aligned with the second optical receive interface 440B and the first optical receive interface 440A is aligned with the second optical transmit interface 430B; and

the optical connection 230 is established using S202 the intermediate mounting structure 510.

Referring to fig. 11, the present disclosure also relates to a method in a radio link transceiver 700, wherein the method comprises:

arranging S301 the optical transmit interface 730A and the optical receive interface 740A on the first radio unit 720A according to the mirror image of the optical receive interface 740B and the optical transmit interface 730B on the second radio unit 720B, respectively, such that when the first radio unit 720A is aligned with the optical interfaces 730A, 740A facing the optical interfaces 730B, 740B of the second radio unit 720B, the optical transmit interface 730A of the first radio unit 720A is aligned with the optical receive interface 740B of the second radio unit 720B, and the optical receive interface 740A of the first radio unit 720A is aligned with the optical transmit interface 730B of the second radio unit 720B; and

each optical transmit interface 730A, 730B and each optical receive interface 740A, 740B are used S302 to transmit cross-polarized signals between radio units 720A, 720B for cross-polarization interference cancellation, XPIC.

According to some aspects, the method includes using the light directing arrangement 750 of the mounting structure 710 to direct light between the light transmitting interfaces 730A, 730B and the respective light receiving interfaces 740A, 740B.

The disclosure is not limited to the examples described above, but may be varied freely within the scope of the appended claims. For example, the cross-polarized signal includes an analog signal and/or a digital signal.

According to some aspects, the cross-polarization signal comprises a control signal.