EP1254464A1

EP1254464A1 - Connection system for submarine acoustic antenna

Info

Publication number: EP1254464A1
Application number: EP00977630A
Authority: EP
Inventors: Daniel Thales Intellectual Property Billet
Original assignee: Thales Underwater Systems SAS
Current assignee: Thales Underwater Systems SAS
Priority date: 1999-11-19
Filing date: 2000-11-07
Publication date: 2002-11-06
Also published as: JP2003514474A; NO20022347D0; FR2801417B1; NO20022347L; WO2001037294A1; US6811327B1; FR2801417A1; NO322803B1

Abstract

The invention concerns connection systems for a submarine acoustic antenna. It consists in connecting the antenna (201-206) to elements (102) of the sonar by an optical link. A removable transformer (210, 211) enables to separate galvanically the antenna and the transmission means. It powers a VCSEL electro-optical element (216) which energises an optical fibre (217) connected to the pressure hull penetrators (108). The invention enables to produce an antenna having a very large number of sensors.

Description

CONNECTION SYSTEM FOR UNDERWATER ACOUSTIC ANTENNA

The present invention relates to connection systems which make it possible to connect the underwater acoustic antennas to the electronic devices for processing these signals which are located inside the hull of a submarine, the antennas being themselves same located outside of this hull.

Sonar antennas, more particularly reception antennas, are located outside the carrier building, for example a submarine, and are conventionally connected to electronic bays which make it possible to exploit the signals transmitted and received by these antennas, using a set of electrical connections that pass through the hull of this building.

This arrangement involves numerous drawbacks, in particular a loss of tightness at the level of the connectors, a large number of cables, junction boxes and shell passages (PHP for Pressure Hull Penetrator), costs induced by the wiring, the controls, ..., very high, reduced reliability of the assembly due to the large number of devices used to establish these connections, and finally a risk of rupture of the seal when it is necessary to replace one ^' sensors. Thus, if we wanted to connect a cylindrical antenna comprising 128 columns of 16 hydrophones, or 2048 channels, by using them all to carry out a processing in deposit and in site, we would have to use between the antenna and the PHP 128 connectors on the columns and on the cables, 128 cables formed of 18 shielded pairs, 128 connectors on the cables and on the PHP, for a total of 512 wet connectors. With regard to PHP, it would then be necessary to use 32 cables of 18 shielded pairs provided with 2 times 32 bases, each base having 4 connectors, 32 electronic boxes to condition the signals, and 32 cables provided with 2 times 32 bases for connect these packaging boxes to the electronic bay.

Such an embodiment cannot in practice be implemented, as well because of the cost of the wiring, which can reach several tens of MF, the weight of cables and connectors, which would be around 6 tonnes, and the very large number of PHP and wet connectors.

To be able nevertheless to use an antenna of this type, very useful for the fine localization of the sources of acoustic noise, and to overcome these drawbacks, the invention proposes a connection system for underwater acoustics, mainly characterized in that it comprises a removable transformer comprising an internal part supplied by the signals to be transmitted and embedded in a first block with the antenna organs and an external part embedded in a second block, magnetically connected to the first part and comprising an electrooptical transmitter powered electrically by this second part for optically transmitting the signals of the antenna over an optical fiber connected to the organs for processing these signals.

According to another characteristic, the electro-optical transmitter is a VCSEL.

Other features and advantages of the invention will appear clearly in the following description, given by way of nonlimiting example with reference to the appended figures which represent:

• Figure 1, a block diagram of a system according to the invention;

• Figure 2, the detailed diagram of one of the channels of Figure 1;

• Figure 3, a detail of an optical connection of Figure 2;

• Figure 4, a cross section of a sheet of optical fiber used in the diagram of Figure 2; • Figures 5 and 6, respectively sectional and front views of a connection system of these optical fibers;

• Figure 7, a top view of the attachment to the hull of a building carrying a set of power outlets;

• Figure 8, a sectional view of the cables of Figure 7 between two sockets; and

• Figure 9, a sectional view of the same cables at a socket.

There is shown in Figure 1, the diagram of a connection system according to the invention for connecting a cylindrical acoustic antenna 101 of the type mentioned above to a sonar bay 102. As For example, each antenna includes 128 columns of 16 hydrophones, plus amplifiers (PA), analog-to-digital converters (ADC), multiplexers (MUX) and the connections corresponding to each column. These connections are connected by an optical coupling system

103 to eight sets 104 of 8 optical fibers making it possible to send out the reception signals and to eight sets 105 of 8 optical fibers making it possible to bring the control signals of the latter to the antenna.

The ends of these sets of optical fibers, which form cables, are overmolded on optical-electrical converters 106 for the output signals and electrical-optical converters 107 for the control signals.

These converters are connected to connectors for crossing the hull PHP, respectively 108 for the converters 106 and 109 for the converters 107. These PHP make it possible to bring the signals inside the thick hull 110 of a submarine.

The PHP 108 and 109 are then connected to the sonar bay 102 by cables 111 and 112.

There is shown more precisely in FIG. 2, all of the connection elements corresponding to a column formed of 16 hydrophones 201 molded with their annex elements in a block 202 of plastic material transparent to acoustic waves, conventionally formed of polyurethane.

To each hydrophone 201 is connected an amplifier (PA) 203, itself connected to an analog-digital converter (ADC) 204.

All of these analog-to-digital converters are connected to a multiplexer (MUX) 205, which makes it possible to multiplex the signals of all the hydrophones on a single output 206.

In the example described, these hydrophones form a column of a cylindrical type antenna, but it could be an acoustic antenna of any type, for example a flank antenna panel for a submarine, or an antenna section towed linear acoustics.

All of the electronic circuits 203, 204 and 205 are, in this embodiment, enclosed in a metal box 207 which makes it possible to obtain effective shielding by being connected to ground by a leaktight ground connection 208.

The electrical supply arrives via a lateral socket 209, which is itself waterproof. The box 207 is filled with a product making it possible to withstand the hydrostatic pressure, for example an insulating mineral oil or polyurethane like that which constitutes the block 202.

According to the invention, the digital data originating from the multiplexer are extracted from block 202 using a removable pulse transformer which makes it possible both to transmit the pulses in a known manner with a low time constant, and to be separated into two pieces, one remaining coated in the mass of polyurethane 202 and the other being external to this mass and connected to the connection cable 217 to the sonar bay. In this way, it is easy to disconnect the entire column and its ancillary members without breaking the seal.

For this, this transformer comprises a core formed by a first internal part 210 which is embedded in the polyurethane 202, and a second external part 211 which is external to this block of polyurethane. The junction faces of the part 210 with the part 211, forming an air gap, are flush with the surface of the block 202. A primer 212 is wound on the internal part 210 of the core. It is supplied by an amplifier 212 which receives the data supplied by the multiplexer 205.

The second part 211 of the core is itself molded in another block of polyurethane 214, of smaller size, and the contact faces of this second part with the first part are themselves flush with the surface of this second block 214 This second block can be fixed to the surface of the first by fixing means (not shown), clips or screws for example, so that the magnetic continuity between the two parts 210 and 211 of the core is best achieved. Under these conditions, the magnetic flux induced by the primary 212 induces in a secondary 215 wound on the second part 211 of the magnetic core an electrical voltage representative of the signals leaving the multiplexer 205.

This secondary 215 is connected to an electrooptical component 216 which makes it possible to convert these electrical signals into optical signals. The invention proposes that this optical component is a component known under the name of VCSEL, acronym of the Anglo-Saxon expression Vertical Cavity Surface Emitting Laser, which makes it possible to emit light signals perpendicular to its surface. These light signals are then taken up by an optical fiber

217, which is overmolded in the second polyurethane block 214 so that its end is just opposite the place from which the light signals of the electrooptical component 216 emerge. The coupling between the fiber and the component can be carried out either directly or through a waveguide to facilitate the manufacture of the assembly. The material used to manufacture the second block 214 being transparent to light, there is no particular precaution to be taken during overmolding to avoid interruption of the passage of light signals due to infiltration of the overmolding product. The assembly thus forms a contactless connection between the hydrophone column fitted with its electronic adaptation members and the cable allowing it to be connected to the connection assembly to the sonar bay 102.

The use of a component of the VCSEL type for producing the system according to the invention is particularly advantageous since the light output mode of this component allows easy adaptation to the optical fiber of transmission, as already explained above. In addition, this component operates with current, and the value of this current is approximately 1 mA with a consumption of the order of milliwatt, which is low and particularly suitable there also for the possibilities of transmission using a transformer of the type described above. In addition, the wavelengths that can be used can vary between 650 nm and 1100 nm, which again is well suited to transmission by optical fiber. In a preferred embodiment, a wavelength of 850 nm will be used.

For more information on this type of component, refer to the IEEE Spectrum publication of February 1998, page 43.

Even with a good adjustment, the dismantling characteristic of the transformer 210-211 leads to the existence of an air gap which is relatively large and has fairly dispersed characteristics, in particular depending on the successive dismantling and reassembly. The coupling between the primary and secondary of the transformer is therefore relatively loose and not mastered. To then be able to operate the component 216 with a modulation current adapted to these characteristics, a feedback system is used comprising a secondary winding 218 wound on the first part 210 of the magnetic circuit of the transformer. This winding by means of an adaptation circuit, comprising for example a rectification system, makes it possible to control the gain of the amplifier 213.

The optical fibers 217 corresponding to the various columns of the antenna are then grouped together in cables which are connected to the device for collecting optical data and for optical-electrical conversion 106.

The invention proposes to produce these cables in the form of a flat cable as shown in FIG. 4, which is formed by overmolding of the optical fibers 217 assembled side by side in the form of a sheet with a coating of a material. plastic, preferably there also polyurethane to achieve continuity with the block 214. Overmolding is carried out in such a way that it has grooves 402 and 403 located between the different fibers on each of the faces of the flat ribbon formed by the cable. This makes it possible to easily separate the fibers provided with their coating, so as to facilitate mounting on the devices 106, if necessary by making ease loops.

It is necessary to send to the electronic members connected to the hydrophones a set of control signals such as clock, synchronization, gain control signals, etc. For this, the invention proposes to transmit these signals by fibers optics 218 which are inserted in a blind hole 219 formed on one of the faces of the block 202 for overmolding the column of the antenna. This hole is located opposite a photodiode 220 which is excited by the light signals coming from the fiber 218. The electrical signals emitted by this diode in response to these light signals are then decoded in a conditioning circuit 221 which makes it possible to select the different signals necessary for amplifiers 203 as well as analog-to-digital converters 204 and for multiplexers 205. This selection is made for example by decoding a digital frame comprising all the necessary signals according to a pre-established coding. The fibers 218 coming from the optical electrical conversion and optical control distribution device 107 will preferably be gathered in the form of a flat cable like the optical fibers 217. To facilitate coupling between the end of the fiber 218 and the photodiode 220, the invention proposes to use a known type of fiber known as “with a large heart” which makes it possible to obtain a relatively wide light beam 222 such that it can compensate for any positioning and alignment faults between the end of the fiber and the photodiode. To connect the optical fibers 217 to the device 106, a small device such as that shown in longitudinal section in Figure 5 and in cross section in Figure 6 is made for example.

This device comprises a flat parallelepiped housing 501 into which is inserted a part 502 forming a vice for clamping the fibers. This part comprises longitudinal V-shaped grooves which make it possible to maintain the fibers 217 coated in the material 401 forming the flat cable after separation at the level of the grooves 402 and 403. As this coating is soft, it molds in the grooves, which ensures the tightness of the assembly at this level. The optical-electrical conversion system is formed by photodiodes 504 fixed on the inner and lower face of the internal cavity delimited by the housing 501. If necessary, these photodiodes will be collected in an ASIC, which will make it possible to integrate into this device a certain number of additional functions allowing for example an amplification of the signals and / or a multiplexing of these. To couple the fibers to the photodiodes, a mirror 505 inclined at 45 ° and used between the end of the fibers and the input faces of the photodiodes will be used, for example.

The entire cavity will be filled with a transparent dielectric oil or gel to withstand the pressure. This gel will be introduced through an orifice then plugged with a plug 506.

The electrical signals will exit by shielded pairs 507. In an alternative embodiment, this ASIC will be produced in a monolithic form, which will make it possible to use a waveguide integrated into the substrate of the ASIC in order to be able to directly couple the fibers to this guide wave. In this way, we can thus remove the mirror and the filling oil.

Likewise, the device for electrical-optical conversion and distribution of the optical control signals to the fibers 218 is produced with a device similar to that of FIGS. 5 and 6. The difference relates to the replacement of the receiving photodiodes by light-emitting diodes emitting. In a preferred embodiment, components of the VCSEL type, like components 216 of FIG. 2, will be used in place of light-emitting diodes. To obtain redundancy of the system, which allows fault tolerance, the invention also proposes, as shown in FIG. 3, using two optical transmitters, DVCSEL for example, 226 and 236 connected in parallel on the terminals of the secondary 215. These components will then be connected head to tail so that the failure of one does not not hinder the functioning of the other. These two components will be connected respectively to two optical fibers 227 and 237 which will lead to optical duplexers 301 and 302. Each of these duplexers will then be connected respectively to two collection devices 306 and 316, which allows in total to ensure redundancy complete by always having the transformer output signals available on one of these two devices 306 and 316.

Finally, to obtain a system which is entirely without electrical contact and which can be entirely dismantled, the invention proposes to supply each antenna element 202 with an induction system by means of a dismountable transformer, as shown in FIGS. 7, 8 and 9 For this, the socket 209 in FIG. 2 is replaced by a part 901 of a magnetic core comprising this part 901 and a second part 902 allowing the magnetic circuit to be closed. Part 901 is in the shape of a "U" and embedded in the polyurethane block 202, while part 902 is linear and allows the magnetic circuit to be closed. This part 902 is itself fixed on a spacer 903, itself fixed on the shell 110 on which the antenna is fixed. This makes it possible to avoid dispersions of the magnetic flux in this shell.

A secondary 904 wound on the part 901 of the magnetic circuit makes it possible to supply the electronic elements embedded in the block 202. To supply the transformer, a primary formed from multi-strand cables 905 is used which form loops which pass through the internal hollow of the magnetic circuit 901/902 and are looped outside thereof as shown in FIG. 7. These cables 905 are supplied with electrical energy from a junction box 906 which makes it possible to leak out electrical energy from the interior of the shell 110. This junction box will preferably be located above the line of buoyancy buoyancy, to facilitate repairs at this level of course. This waterline in the case of a submarine will be that existing when it is on the surface.

To have sufficient coupling, multi-strand cables will be used, each strand of which is traversed by the same current and, where appropriate, several multi-strand cables of this type, 2 in the case shown in the figures. To minimize losses of any kind between the transformers, which we find that they actually form contactless electrical sockets, these cables will be gathered between these sockets as shown in FIG. 8.

Claims

1 - Connection system for underwater acoustics, characterized in that it comprises a removable transformer comprising an internal part (210) supplied by the signals to be transmitted and embedded in a first block (202) with the organs of the antenna (201-206) and an external part (214) embedded in a second block (214), magnetically connected to the first part and comprising an electrooptical transmitter (216) electrically powered by this second part for optically transmitting the signals of the antenna on an optical fiber (217) connected to the organs for processing these signals.

2 - System according to claim 1, characterized in that the electro-optical transmitter is a VCSEL (216).