Development, Testing and Track Record of Multi-Way Underwater- Mateable Fiber-Optic Connectors for Deepwater Applications
Gary Brown and Matt Christiansen take us through an overview of the lessons learned in design, development and testing, plus a summary of the track record, of a full range of underwater-mateable fiber-optic connectors.
This has enabled underwater-mateable fiber-optic connectors to join the subsea industry’s selection of proven components for deepwater and ultra-deepwater applications.
Subsea Optical Communication Systems
Underwater optical fiber and communication systems have been in use in the offshore and subsea oil and gas environs for many years now. The main advantages of such systems are now well known, for example:
- Significant increase in communication bandwidth
- Significant increase in speed of data transfer
- Significant increase in communication distances
- Immunity to electrical noise
- Potential cost reduction in subsea umbilical construction and installation by enabling the
- manufacture of smaller diameter umbilicals
- Well-known temperature dependent properties of optical fiber
It is however the use of wet-mate optical connectors that has enabled modular underwater installation and this combined with the advantages above have allowed a significant growth in the following:
- Increasing quantity, speed and sophistication of remote, distant underwater monitoring and control
- Significantly faster underwater seismic streamer array processing
- Next generation subsea Christmas tree and manifold systems
- Subsea separation, subsea processing and subsea production boosting systems
- Significantly longer step-out distances for remote well locations or subsea satellites
- Real-time assessment of reservoir performance and optimization
- Real-time health and status monitoring of subsea equipment for safety and to better understand equipment maintenance regimes
- Greater opportunity to access large quantities of raw subsea data
- The use of high power transmission systems which rule out conventional electrical data communications due to Electro Magnetic Interference (EMI)
- The opening up of long distance (200km) shore to field opportunitie
It is the advent of these newer technologies moving into the subsea environs and in deeper waters that have created not only the need for optical wet-mateable connector products but also the number and increasing diversity of them as well.
The Challenge of Wet-Mate Fiber Optic Connectors
As a very brief introduction to fiber optical communications, the principle of operation exploits the ability of light to travel efficiently within a very fine glass fiber. The glass fiber is essentially an optical wave-guide in which light stays trapped within the core by near total internal reflection between the core and it’s outer cladding. The core consists of a 9µm diameter high refractive index glass material covered by a 125µm diameter lower refractive index cladding.
For comparison of size a human hair is 90µm diameter. The 125µm cladding may also be covered in a protective coating to a diameter of 250µm that subsequently may also be covered by a secondary coating to 900µm.
The main challenges of wet-mate fiber optic connector design and manufacture are:
- The alignment and coupling of these very fine 9µm diameter glass fibers underwater without any contamination across the optical faces
- The alignment and coupling of these very fine 9µm diameter glass fibers underwater without high optical losses
- The ability to operate underwater for long periods of time underwater without discernable degradation
Specifications for Optical Wet-Mate Connectors
The demand for optical applications is increasing and not only are the quantity of optical system products increasing but so too is the variety and complexity of the many and varied applications required. These in turn affect the customer’s requirement for optical wet-mateable connectors. These varied technical and commercial requirements include but are not limited to those extremes identified below.
These points all have an impact on product design, development, cost, qualification and availability:
- Long term (25 years plus)
- Short term (months only)
- Optical Losses
- As low as possible (≤ 0.5dB)
- ≤ 2dB
- As small as possible
- Don’t care
- Must be inexpensive
- Don’t care but not exorbitant
- ROV, AUV, Diver, Stab-plate
- Non-corrosive metal body materials
- Non-metallic body material
- ROV Handle
- T-bar, H-handle, Fishtail-handle
- ISO 13628-8 Design & Operation of ROV Interfaces on subsea production systems
- Low or high temperature only
- Wide operational temperature
- Single channel only
- Between 4 and 8 channels
- As many as possible
- Cable termination
- Hose termination
- Strength member termination
- Fit for purpose
- Extensive test program to meet operational requirements
- Test to extremes
In each case these requirements are assessed for compatibility with current products in an attempt to standardize product elements.
In many cases there are technical, physical or commercial constraints that require alternative solutions, especially when the quantities are significant and the costs can be justified.
Over the last few years this increasing trend from customers has led to the development of a family of several different wet-mateable optical products that are proving very successful.
This has resulted in the availability of this range of products, thus allowing more technical and commercial choice of field proven products for the end-user.
These requirements are increasing in both numbers and variety and with it wet-mate optical connectors are already being used on the following systems, which we know of:
- Qualification & evaluation programs
- Subsea control systems
- Norsk Hydro Troll pilot project
- Burullus Scarab/Saffron project
- Norsk Hydro Fram Vest project
- Phillips Little Dotty project
- Petrobras SBMS multiphase pump project
- Downhole instrumentation – Shell ETAP project
- Seabed seismic system – BP East Foinhaven project
- Deepwater drilling systems
- ANTARES Project – subsea optical telescope, in the Mediterranean, designed for the detection of Neutrinos
- Qualification & evaluation programs
- Classified Defense projects
In the next post we go on to look at the development process in more depth with the HYDRALIGHT wet-mate optical connector.