Ship/Shore Communication Link System (hereafter SSCLS)
between LNG carriers and the shore terminals was first developed
with local application technology using the light source of
850nm LED locally by Furukawa of a Japanese company approx.
25 years ago. Since then, this system has been installed at
overseas LNG terminals and onboard LNG carriers and is still
being used.
LED (Light Emitting Diode) is the technology developed at the
early stage of fiber optic communications and usually applied
to general industries, not for communications use. As normal
LEDs are produced for the wavelength of 400~700nm range, LED
of 850nm is classified as special and has complicated manufacturing
processes. In case of VCSEL, commercial products are available
at 850nm as Well as 1,310nm and now 1,550nm is under development.
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| GMB has developed SSCLS to be fully compatible with 850nm
LED system using 850nm VCSEL light source without any change
to terminal side SSCLS and fiber optic cable. GMB SSCLS is expandable
to other field like internet communication,
The fiber optical link for LNGC ship/shore communication
system shall be installed to communicate between LNG ship
and LNG shore terminal through fiber optical cables. The fiber
optical ship/shore link (FO SSL) comprises 4 channels of multiplexed
communication data and Emergency Shut Down Signals of ship
to shore and shore to ship.
Communication signals are divided into audio signals such
as mooring tension monitor, telephone voice and interphone
voice and contact signals of emergency shutdown.
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When developing an alternative system to cope with the unavailability
of 850nm LED, the compatibility with the existing system and
economical aspects can never be overlooked. 850nm VCSEL can
be one of the solutions to come up with. The advantage of 850nm
VCSEL is that the wavelength is the same as 850nm LED and the
multimode optical fiber can be used and this is suggested that
the existing 850 LED system installed on the LNGCs and LNG terminals
still be available to use continuously subject to apply 850nm
VCSEL. This ensures complete compatibility with the existing
850nm LED system. As 850nm VCSEL is a module of light source
developed for communications use, this can be adopted to communicate
through the existing fiber optical cables for high-speed communications
without any extra hardware installations.
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LED type
SSCLS
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LD type
SSCLS
|
VCSEL
type
SSCLS |
| Light Source |
LED |
LD |
VCSEL |
| Wave length |
850nm |
1310nm |
850nm |
| Beam type |
Edge |
Edge |
Vertical |
| elliptical |
elliptical |
Symmetrical |
| Cable mode |
Multi mode |
Single mode |
Multi mode |
| Comm. length |
Within 600m |
Within 10km |
Within 1000m |
| compatibility |
Yes |
No |
Yes |
| Continuity of Product |
No |
Yes |
Yes |
| Internet communication |
No |
Yes |
Yes |
| <
Table : Comparison between each light source> |
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3
voice and 1 data channels, multiplexed |
- Transmission scheme : Full duplex, 2wires, Both side
band(BSB) method
- Number of channels : 4 channels
- Modulation scheme : Frequency shift method (carrier frequency
±2.6 kHz)
- Frequency allocation : Full duplex, 2 wires
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| Optical
Transmitter / Receiver(T/R) Unit |
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- Number of fibers : 2 cores
- Optical wave length : 0/85±0.03§(E/O : VCSEL, O/E : PIN-PD)
- Applicable optical connector : ST type
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- Signal provider by tone for normal safe mode and normal
ESD mode.
- Fail safe operation function
- Output : Dry contact signal
- Number of Signal : Transmitter, Receiver 1 point each
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