The rest of the final splice process involves the following.
Once the splices are complete, they are tested again with an OTDR from one of the cable stations. If anything is out of specification, the offending splices will be broken and re-made.
Once the fibres have passed the OTDR test, they are wrapped up inside the joint housing. They are OTDR tested again to make sure that nothing has happened to them.
The moulding process is used to seal the joint and create a continuous plastic casing around the entire joint. The process involves melting down plastic pellets and injecting them in to a mould at very high pressures and temperatures. Once set-up, the joint is OTDR’d again!
The moulding process is critical to the joint withstanding being on the seabed for a long time. Any air bubbles, cracks or foreign objects in the completed mould have to be examined and recorded against the acceptance criteria for the system. If it fails, it has to be cut out and re-moulded. The completed mould is x-rayed and assessed. The ship carries a portable x-ray machine and a dark room for processing the image. Again, once complete, the joint is OTDR’d to make sure everything is OK.
Once it has been OTDR’d for the last time, it is closed up. This means that the bend limiting boots are attached and any plastic outer casings are attached (if required). The joint is then handed over to the Deck Department to start the final bight deployment.
Once the joint is in the water, the system is powered up and tested both optically and electrically. As you can see it is a very involved and lengthy process but every step has to be followed exactly or the ship would end up having to recover the joint and start all over again.
So what do we mean by final splice?
The process of creating the final splice is a lot more involved than you would normally think. If you’ve already taken a look at the photos in the gallery you will see that it can take a while. A non-armoured joint takes in the region of 12-14 hours to complete. If it was an armoured joint, then this time can be up to 24 hours.
This involves cutting back the poly outer layer and exposing the copper power and fibre packages in very specific lengths (all measured to the nearest mm). The fibres and copper conductor are tested at this point to ensure nothing has been damaged.
Once prepared, each end has to have a socket attached. This is a cone shaped piece of metal that acts as the connection to the joint itself. This is then pressed (using a hydraulic ram) on to the cable end. Each end is then tested with an optoelectronic instrument (an “OTDR”) to ensure that the fibres haven’t been damaged.
The sockets are then bolted to the main joint housing ready to lay out the fibres to start fusion splicing. The fibres are carefully positioned to allow the bend radius to be maintained as well as laid out to ensure that nothing gets tangled up. Anything that could present a snag hazard (such as screw heads) is taped up to make the interior of the joint as smooth as possible. Breaking a fibre at this stage could mean cutting everything off and starting again.
Each fusion splice is quite involved and includes the following specific steps.
- Removing the colour cladding to expose the glass.
- Cleaning the fibre in an acetone bath.
- Cleaving the fibre for a 90 degree cut.
- Cleaning the fibre in an acetone bath.
- Setting the fibre in the splice housing (a magnetic clamp that holds the fibre in the right position).
- Lining the 2 fibres up in the fusion machine.
- Conducting the splice itself.
- Taking a photograph of the splice and recording the estimated splice loss.
- Strength testing the splice.
- Applying the strength member/heatshrink.
At 13:45 today, the first light was successfully transmitted and received across the system between Sydney and Guam. This major milestone has been able to be achieved as yesterday the team on the Tyco Durable completed the final splice on the system just off Madang. The work was completed in the early hours of yesterday morning and the PIPE International and Tyco Telecom teams have been conducting the various optical and powering tests and assessments to ensure that everything is as it should be. This also means that for the first time, Sydney, Guam and Madang are connected by a continuous piece of fibre-optic glass.
With the OK being granted by the cable station engineers, the C.S. Tyco Durable has been released from the cable grounds. This marks the completion of the marine programme.
Watch this blog for further information and a gallery of photos will be included in the next 24 hours.
So your next question is probably: how does the ROV perform the PLIB operations?
The first step involves sending the ROV down to beam back to the ship video and data of the area in which the cable is located. This survey or measurement pass involves: ascertaining the condition of the cable on the seabed; viewing any obstructions that may hinder any burial operations; and measuring the depth of the cable. The depth of the cable can be measured passively using a pulse induction technique which is similar to that used by a metal detector. (The hardware used to perform this is the grill on the ROV)
Once the cable has been located and it is determined that the seafloor is jettable then the ROV can be used to conduct further burial works. These works involve lowering the jetting tool on the ROV nearer the cable and using the jet to fluidize the seabed material to create a trench for the cable to nestle in. The picture above shows snapshot video of the surface laid cable on the seabed about to be jetted under the surface. The burial depth under normal conditions is approximately one meter beneath the seabed.
One of the last yet more important steps of the marine installation is the Post Lay Inspection and Burial (or “PLIB“) operation. This step occurs after the plough burial operations. The PLIB works are necessary as sometimes the plough burial operations cannot be performed (e.g. where the cable is in close proximity to another cable) and they are also a means by which the cable can be inspected for conformity with the specifications. The means by which the PLIB operations are conducted are via a Remotely Operated Vehicle (“ROV“) like the one pictured above.
During the CS Tyco Durable’s laying programme, she will have to launch the four branching units (“BUs”) that will allow PIPE International to expand the system. This sounds relatively easy but the logistics are fairly complicated. A BU has three legs: Trunk, A1 & A2. Therefore it has 3 cables that need to be managed. This means that it cannot leave via the Linear Cable Engine (“LCE“) which can only handle a cable in a straight line.
And so starts a process of swapping the cable from the LCE to the Cable Drums (pictured) and from there controlling the payout of all three cables to ensure that the BU doesn’t twist as it is being deployed. The three cables need to land in the correct orientation or you will end up with crossed legs.
The whole process takes several hours and includes a few stops and starts and winding cable on and off the Cable Drums as the BU passes down the ship. Once it gets to the end of the highway it has to be transferred out on to a trolley for its trip along the aft deck. The 10T crane is also called in at this point to help with the manoeuvrers. With the cables no longer on the drum engines the crew apply a series of stopper and chains to take the tension and stop the BU making a bolt for the seabed too quickly. At each step of the process, the stoppers are moved down the deck to keep everything safe and under control.
Once the trunk leg of the BU (which is always the last to leave) is overboarded, a hatch opens in the rear wall of the Highway to allow the cable to be transferred back to the LCE. With this done, everyone prepares to continue the main cable laying.
As of Thursday 22rd July the Tyco Durable is at latitude 16 degrees 46.88 minutes south as seen from the figure above. The lay is now going extremely well and we hope to lay BU3 before the weekend. Once this is complete the vessel will finish off the installation with a run to the BU4 position off Madang. Current plan is for a final splice around 20th August 2009.
This photo is the S1.1 joint going over after we had recovered the buoy.
The Tyco Durable is currently back in port in Sydney. After all repairs are complete and we have our new plough team on board we will complete the remainder of the burial of S1.1 off Sydney. We will then inspect and post-lay bury as required the Sydney shallow water cable. We expect this (with no weather delays) to take less than a week to complete and then we will continue laying from Brisbane north.
The Tyco Durable has now completed S1.2 between Brisbane and Sydney. This included the deployment of BU1 in 4500 metres of water off Sydney and as part of this the deployment of the S2 stub for future connection to New Zealand.
This photo was a buoy we laid that had the Sydney end of the cable attached while we went further east to deploy the stub cable. We took this photo as we were returning to pick up the buoy to join it to the BU. The Tyco Durable has now returned to Sydney to have the winch repaired and reload the plough team.
It has been an interesting few weeks for the Tyco Durable as we lay the remaining portion of PPC-1 up the Australian coast. We have had some tricky weather for ploughing, namely a severe storm on 21st May. As some of you may be aware, we have had some equipment problems, specifically the large tow winch for the plough needs spare parts and major repairs in order for us to complete the ploughing off Sydney.
Despite these setbacks we have continued on and have laid BU1 off Sydney and all of the cable between Sydney and the BU2 location (Brisbane). We are currently 170km to the east of the Brisbane CBD streaming the last of the segment from Sydney.
The plan is for the ship to return to Sydney today to complete the winch repairs and then the remaining Sydney burial works before returning to pick up where we have left off and continue the final parts of the lay up to the final splice position off Madang.
Photo courtesy of James Freeman of the Nautical Association of Australia