Data transfer apparatus

1. A subsea data transfer apparatus for subsea transfer of data from a first part of a subsea measuring apparatus to a second part of the subsea measuring apparatus when the first part is rotating relative to the second part, the data transfer apparatus comprising:

at least one signal transmitter mounted to the first part of the subsea measuring apparatus and having at least one first antenna for receiving first electrical signals representing data from the first part and emitting data-carrying electromagnetic radiation corresponding to said first electrical signals; and

at least one signal receiver mounted to the second part of the subsea measuring apparatus such that the at least one signal receiver is separated from and rotates relative to the, or each one of the, at least one signal transmitter, wherein said at least one signal receiver comprises at least one second antenna for receiving said data-carrying electromagnetic radiation and generating second electrical signals corresponding to said first electrical signals;

wherein, with said first part and said second part located within water beneath sea surface, said at least one signal transmitter and/or said at least one signal receiver includes respective radiation guide adapted to cause less attenuation of said data-carrying electromagnetic radiation passing through said radiation guide than when passing through the water, said data-carrying electromagnetic radiation continuously transmitted from said at least one signal transmitter to said at least one signal receiver, and at least some of said data-carrying electromagnetic radiation is transmitted from said first antenna to said second antenna via a path including said at least one radiation guide.

2. The subsea data transfer apparatus according to claim 1 , wherein (i) said at least one signal transmitter is adapted to receive second data carrying electromagnetic radiation corresponding to data from said at least one signal receiver, and/or (ii) said at least one signal receiver is adapted to transmit the second data-carrying electromagnetic radiation to said at least one signal transmitter.

3. The subsea data transfer apparatus according to claim 1 , further comprising a reflector for reflecting at least part of said data-carrying electromagnetic radiation travelling towards a surface of said at least one signal transmitter and/or said at least one signal receiver.

4. The subsea data transfer apparatus according to claim 3 , wherein the reflector comprises at least one reflective coating on said at least one signal transmitter and/or said at least one signal receiver.

5. The subsea data transfer apparatus according to claim 3 , wherein the reflector is provided on said at least one signal transmitter and is adapted to direct at least some of said data-carrying electromagnetic radiation towards said at least one signal receiver.

6. The subsea data transfer apparatus according to claim 1 , wherein said at least one signal transmitter has an internal profile adapted to direct at least some of said data-carrying electromagnetic radiation towards said at least one signal receiver.

7. The subsea data transfer apparatus according to claim 1 , wherein said at least one radiation guide forms a closed loop.

8. The subsea data transfer apparatus according to claim 7 , wherein said at least one radiation guide is substantially annular.

9. The subsea data transfer apparatus according to claim 1 , wherein said at least one signal transmitter and at least one signal receiver each comprises said respective radiation guide.

10. An apparatus according to claim 1 , wherein said at least one radiation guide comprises at least one plastic material and/or at least one rubber material.

11. The subsea data transfer apparatus according to claim 1 , wherein at least one radiation guide is adapted to transmit and/or receive at least part of said data-carrying electromagnetic radiation in a direction substantially parallel to an axis of rotation of said first part relative to said second part.

12. The subsea data transfer apparatus according to claim 1 , wherein the apparatus is adapted to generate said data-carrying electromagnetic radiation having a frequency of 0.3 GHz to 300 GHz.

13. The subsea data transfer apparatus according to claim 12 , wherein the apparatus is adapted to generate said data-carrying electromagnetic radiation having a frequency of 2 GHz to 11 GHz.

14. The subsea data transfer apparatus according to claim 13 , wherein the apparatus is adapted to generate said data-carrying electromagnetic radiation having a frequency of 2.4 GHz to 2.5 GHz.

15. The subsea data transfer apparatus according to claim 2 , further comprising a reflector for reflecting at least part of said data-carrying electromagnetic radiation and/or said second data-carrying electromagnetic radiation travelling towards a surface of at least one signal transmitting part and/or said at least one signal receiver.

16. The subsea data transfer apparatus according to claim 4 , wherein the reflector is provided on said at least one signal transmitter and is adapted to direct at least some of said data-carrying electromagnetic radiation towards at least one said signal receiving part.

17. A subsea measuring apparatus comprising (i) a first part for mounting on an object, (ii) a second part rotatably mounted on said first part and having at least one radiation source for causing data-carrying electromagnetic radiation to pass through said object, and at least one radiation detector for detecting the data-carrying electromagnetic radiation passing through said object, and (iii) a subsea data transfer apparatus comprising:

at least one signal transmitter mounted to the first part of the subsea measuring apparatus and having at least one first antenna for receiving first electrical signals representing data from the first part and emitting the data-carrying electromagnetic radiation corresponding to said first electrical signals; and

at least one signal receiver mounted to the second part of the subsea measuring apparatus such that the at least one signal receiver is separated from and rotates relative to the, or each one of the, at least one signal transmitter, wherein said at least one signal receiver comprises at least one second antenna for receiving said data-carrying electromagnetic radiation and generating second electrical signals corresponding to said first electrical signals;

wherein, with said first part and said second part located within water beneath sea surface, said at least one signal transmitter and/or said at least one signal receiver includes respective radiation guide adapted to cause less attenuation of said data-carrying electromagnetic radiation passing through said radiation guide than when passing through the water, said data-carrying electromagnetic radiation continuously transmitted from said at least one signal transmitter to said at least one signal receiver, and at least some of said data-carrying electromagnetic radiation is transmitted from said first antenna to said second antenna via a path including said at least one radiation guide.