SEACON Copper v Fiber System Design Considerations - Underwater Intervention 2011 Cable & Connector Workshop - SEACON

Copper v Fiber System Design Considerations – Underwater Intervention 2011 Cable & Connector Workshop

Copper v Fiber
System Design Considerations
Underwater Intervention 2011 Cable & Connector Workshop 

Brad Fisher & Dave Jenkins, SEA CON®

January 2011

  1. Abstract  / Introduction
  2. System Engineering:  Requirements Flowdown
  3. Circuit Pathways: Cable vs PBOF
  4. Copper:  Advantages, Disadvantages, Attributes and Cost Drivers
  5. Fiber:  Advantages, Disadvantages, Attributes and Cost Drivers
  6. Some Structural Concerns
  7. Summary and Comparison


1.  Abstract  / Introduction

  • Copper or Fiber ?  Each has its strengths, and limitations.  The purpose of this paper is to discuss Copper vs. Fiber considerations, when designing a system.  Early in a subsea system design,  the choice regarding the desired pathway for the power, communications and data signals is made
  • System Engineers are faced with straightforward choices.  However, based on the inquiries we receive, he or she is not necessarily fully informed on the cost elements and drivers for Copper vs. Fiber.
  • This paper will attempt to clarify this fundamental design choice, by showing attributes, advantages, disadvantages, and cost drivers for this key design decision.


2.  System Engineering:  Requirements Flowdown

Additional Considerations

Q:  How often has a problem occurred because of connector selection?   

  • Helpful for Connector Company to be on the Design Team Early!

Different Considerations:  Data is Not Power!

  • Communication Circuits
    • Communications Data, Analog or Digital
    • Sensor Information
  • Oceanographic Sensors
  • Electrical Power
    • Equipment power (IE), Recharge batteries


3.  Circuit Pathways:  Cable vs PBOF

Circuit Pathways

  • Cable
    • Type of Jacket
    • Filler Materials
    • “Waterblocking”
    • Conductor gage and material
    • Armor package?
    • Tow cable?
  • PBOF, OFH (Pressure Balanced Oil Filled, Oil Filled Hose)
    • Type of OFH;
      • COTS hose w/clamps
      • Reinforced plastic hose
      • Ruggedized OFH
  • Terminations
    • Clamps, swaged fittings
    • PU or neoprene overmolding
    • Method of termination
    • Strength Termination


4.  Copper:  Advantages, Disadvantages, Attributes and Cost Drivers

Copper Parameters

  • Advantages of Copper
    • Electrical Power Transmission
    • Initial Cost Advantage (Less costly connectors and elex)
    • Legacy System Compatibility
    • Electrical / Copper is a known Technology!
  • Disadvantages of Copper
    • Requires EMI / EMP Shielding
    • Limited in Speed and Bandwidth
    • Increased Weight and Size

Speed: Copper

Technology Speed Physical Medium
POTS (Plain Old Telephone) 56 Kbps Twisted Pair
ISDN 64-128 Kbps Twisted Pair
DSL (home) 128 Kbps Twisted Pair
DSL (business) 512-8 Mbps Twisted Pair
Cable Modem 512 Kbps – 52 Mbps Coax
Ethernet 10 Mbps Twisted Pair
Fast Ethernet 100 Mbps Twisted Sister
Gigabit Ethernet 1 Gbps Twisted Pair / Fiber
OC1 (Sonet) 51.84 Mbps Optical Fiber
OC24 (Sonet) 1.244 Gbps Optical Fiber
OC48 (Sonet) 2.488 Gbps Optical Fiber
OC192 (Sonet) 10 Gbps Optical Fiber

Electrical Requirements

Power

  • Number of conductors
  • Current, Gage
  • VAC, VDC
  • Insulation resistance
  • DWV

Signal

  • Conductors, Current, Voltage
  • Data Rate (Cat 5, 5a,6)
  • Impedance Match
  • Shielding
  • Dielectric materials DWV
  • EMI Shield Term?
  • Coax?

Mechanical Design

  • Materials (GRE, SS, Ti)
  • Thermal
  • WMC/DMC
  • Dielectric Material
  • Coatings
  • Jacket and Bond (match connector to cable)

Copper Parameters: Cost Drivers

Initial Outlay favorable when compared to optical systems (cheaper…)

High density terminations and shield connections are labor intensive.

Materials degradation over time can affect Insulation resistance (not present in fiber), and impact maintenance (or replacement).


5.  Fiber: Advantages, Disadvantages, Attributes and Cost Drivers


General Attributes of Fiber

  • SPEED:  Fiber optic networks operate at high speeds\up into the many gigabits.
  • BANDWIDTH:  Large carrying capacity.
  • DISTANCE:  Signals can be transmitted further without needing to be “refreshed” or strengthened.
  • NOISE/EMI/Shielding:  Greater immunity to electromagnetic noise such as radios, motors or other nearby cables.
  • MAINTENANCE:  Fiber optic cables cost less over time to maintain than copper.

Optical Requirements

  • Optical
    • SM / MM (Single-Mode / Multi-Mode)
    • Nr of Fibers
    • SM or MM
    • Insertion Loss
    • Back Reflection
    • Flat or APC?
  • Mechanical Design
    • Materials
    • Thermal
    • WMC/DMC
    • Fiber Management (Bend radius)
    • Ability to reterm/rework ?
    • R/A vs Straight

Single-Mode vs Multi-Mode

Single-Mode

  • Small core  (8-10 microns)
  • Long haul systems
  • Up to 50-60 km

Multi-Mode

  • Larger core (50-62.5 microns)
  • Short run systems
  • Less costly electronics

Mechanical Design

Some Things to Think About…..

  • Materials Ti, SS?
  • Strength?
  • WMC vs DMC?
  • Thermal Issues at play?
  • Mating cycles?
  • Design life?
  • Cable or PBOF?
  • Pressure requirement (Open face?)
  • Electrical, Optical or Hybrid ?
  • How is it being used?  (Dynamic Tow? Static?)
  • Saltwater, Freshwater, Brackish, Ice?
  • Over the side issues?

Fiber Parameters

Insertion Loss:  Loss of SIGNAL POWER across a device, in dB.  LOW is good – a 0.2dB connector is better than a 1.5dB connector.

Return Loss:  A measure of REFLECTION ENERGY across a device, also in dB (also known as Back Reflection).  HIGH is good – 60dB return loss is better than 30dB return loss.

SEA CON® Typical,  For Dry Mate Connectors

Speed: Fiber

Technology Speed Physical Medium
POTS (Plain Old Telephone) 56 Kbps Twisted Pair
ISDN 64-128 Kbps Twisted Pair
DSL (home) 128 Kbps Twisted Pair
DSL (business) 512-8 Mbps Twisted Pair
Cable Modem 512 Kbps – 52 Mbps Coax
Ethernet 10 Mbps Twisted Pair
Fast Ethernet 100 Mbps Twisted Sister
Gigabit Ethernet 1 Gbps Twisted Pair / Fiber
OC1 (Sonet) 51.84 Mbps Optical Fiber
OC24 (Sonet) 1.244 Gbps Optical Fiber
OC48 (Sonet) 2.488 Gbps Optical Fiber
OC192 (Sonet) 10 Gbps Optical Fiber

Fiber Speed and Bandwidth: Theory

“With wavelengths and values typically used in communication networks, the scientists determined that it is theoretically possible to send 100 terabits of data per second without excessive noise or interference.“


Terabit = 1,000,000,000,000 bits (10 e 12) bits per second

From Journal of Nature 411, 28 June 2001
Nonlinear limits to the information capacity of optical fibre communications
Partha P. Mitra & Jason B. Stark
Bell Laboratories, Lucent Technologies, Murray Hill, New Jersey 07974, USA

Bandwidth

  • 103             Kilobits
  • 106             Megabits
  • 109             Gigabits                →          Where we are today
  • 1012           Terabits                →          The Theoretical limit
  • 1015            Petabits
  • 1018            Exabits
  • 1021            Zettabits
  • 1024            Yottabits
In electronic communication, bandwidth is the width or band of frequencies that an electronic signal uses on a given transmission medium.
Typical voice signal:    Three kilohertz (3 kHz)
Analog TV video signal:   Six megahertz (6 MHz)   (2000x)
Fiber Parameters

Advantages Of Fiber

  • High Bandwidth,  High Speed
  • EMI and EMP Tolerant
  • Lighter weight for large systems

Disadvantages of Fiber

  • Higher Initial Cost
  • Possible pressure dependent loss
  • Requires higher skilled techs
Fiber Parameters: A Consideration

Pressure Dependent Optic Loss:   Where Insertion loss is a function of pressure (not a desirable state)

Pressure Dependent Optic Loss:   Some possible causes include the presence of small air bubbles / air gaps in PBOF systems or an inadequate fiber management (bend radius).

Optical Parameters, Cost Drivers

– Typically a one atmosphere (or compensated pbof) chamber must be incorporated in a molded connector backshell design

– Fiber cable is typically less expensive than copper counterpart, but connector and termination components are more costly

– Labor rate of optically trained techs


6.  Some Structural Concerns

– Overmolded:  Ocean Force Exists to Penetrate Interior of Cable and Overmold.

– Oil Filled Assy:  Full Ocean Pressure Felt on Interior.

Cathodic Delamination

An underwater connector failure mode, related to the use of Zinc anodes for corrosion control of marine metal structures.  An electrochemical potential is developed between the hull zinc anodes and the connector backshell, which are generally connected to the hull.  Salt water is the electrolyte,  with free electrons formed at the cathode (connector backshell).  The effect of the free electrons at the backshell surface is to promote hydroxide ions (OH),  and a local rise in pH. This local basic solution attacks the bond,  and can cause complete delamination over time. The bond failure can lead to a leak path between the boot and backshell.

A simplified ship scenario showing the local OH ions and basic condition.

Preventing Cathodic Delamination

  • Use of GRE connectors
  • Non-conductive coatings (NCC)
  • GRE or non-metallic shells or sleeves


7.  Summary and Comparison


Summary:  Fiber vs Copper

  Advantages Disadvantages
Fiber Bandwidth, speedEMI/EMP TolerantReduced weightCost (Long haul) Additional trainingMore complex termInitial cost
Copper Electrical powerCost AdvantageLegacy systems EMI/EMP ShieldingWeight and size