DESIGNING A UV LED SYSTEM FOR OPTICAL FIBER, WIRE, AND CABLE APPLICATIONS - Eric Nelson, Heraeus Noblelight America, RadTech 2022
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DESIGNING A UV LED SYSTEM FOR OPTICAL FIBER, WIRE, AND CABLE APPLICATIONS Eric Nelson, Heraeus Noblelight America, RadTech 2022
OPTICAL FIBER COATINGS Basic elements of an optical fiber - Core : silica, transmits light - Cladding : silica, lower refractive index to reflect light back into core and reduce light losses - Coating : dual layer UV curable polymers. Thickness varies - 10s to few hundred microns Function of optical fiber coatings - Protect glass fibers from harsh environmental conditions – moisture, chemical contamination - Protect delicate glass fibers from damage during handling or processing - Reduce signal interruption and distortion Applications - Communication - Data transmission - Sensors - Medical RadTech 2022, E. Nelson May 2022 2
OPTICAL FIBER DRAWING TOWER
▪ Preform added to high purity graphite furnace and heated until
molten
▪ Strand of glass falls from bottom of furnace
▪ Pulled through series of dies until required diameter is achieved
and the fiber cools and solidifies
▪ UV curable coatings are applied and cured before winding onto
a spool
▪ 2 coating layers
▪ Coating / cure coating / cure again
▪ Coating / coating / cure both layers
▪ The tractor mechanism pulls the glass line from the preform
▪ Some fiber coating processes run at speeds of 3000 m/min, whereas
others are limited to 50 m/min
▪ Always pushing to run faster – up to 3400 m/min
RadTech 2022, E. Nelson May 2022 3
UV CURING APPLICATIONS IN OPTICAL FIBER
Coating applied to fiber as it is drawn
▪ Protects fiber and provides strength and flexibility as the fiber is drawn and wound
Coloring Inks
▪ Color code the optical fibers for identification purposes and also provide additional
protection for the fibers in multiple fiber cables
Ribbon matrix material
▪ UV curable polymer that encapsulates multiple optical fibers to create ribbon cable
Labelling & marking inks
▪ Finished optical fiber cables use UV ink jet inks for high speed in-line labelling and marking
on the outer jacket for identification
RadTech 2022, E. Nelson May 2022 4
ESTABLISHED UV LAMP SYSTEM FOR OPTICAL FIBER MANUFACTURING
Optical fibre coating established using specifically designed UV discharge bulbs - microwave powered lamps
▪ fiber placed in focal plane of the elliptical reflector to achieve maximum irradiance on the fiber
▪ external light shield and back reflector completes the ellipse of the UV lamp reflector and delivers maximum UV to be
focussed in the vicinity of the fiber
▪ quartz tube for inerting to achieve high DBC rates
RadTech 2022, E. Nelson May 2022 5
UV LED LAMP SYSTEMS IN OPTICAL FIBER COATING
▪ Global optical fiber cable market grows by around 12% annually driven by:
✓ Increasing demand for data
✓ Increasing internet connectivity
✓ Advances to the next mobile generation – 5G
✓ Advances in technology for connectivity in IoT, VR, autonomous vehicles etc
▪ Optical fiber manufacturers are looking to:
✓ Increase productivity
▪ increase draw tower speeds
✓ Reduce operating costs
▪ reduce energy costs
✓ Reduce environmental impact
▪ no mercury
Drive to implement UV LED lamps in their manufacturing process
RadTech 2022, E. Nelson May 2022 6
OBJECTIVE
▪ Several options for UV LED optical designs
▪ Greater freedom of optical design
▪ Easier to implement different reflectors / optics to manage the UV more effectively
What type of optical design of LED lamp systems can manage the photons most efficiently?
Maximize the UV in the active curing area
Minimize the energy required to achieve this
RadTech 2022, E. Nelson May 2022 7
EVALUATION PROCESS
▪ 1x Microwave lamp system and 2x LED systems
▪ For each UV lamp type the following assessments were carried out:
✓ 2D irradiance mapping
✓ Optical simulation (LED lamp systems)
✓ System energy consumption
▪ Quartz tube included in all lamp systems
▪ High speed draw tower curing test of optimized optical arrangement
RadTech 2022, E. Nelson May 2022 8
UV LED LAMPS EVALUATED
▪ Linear array, focussing optics & small back
reflector
▪ Higher optical energy input ▪ Uses significantly fewer LEDs
▪ Small form factor so can position 3 arrays
▪ Relies on back reflector to direct UV ▪ Optics and back reflector increases
around the fiber
rays into the curing area the peak intensity in the curing area
▪ Very high irradiance in curing area with lower
& onto the fiber
energy consumption
RadTech 2022, E. Nelson May 2022 9
UV LAMP SYSTEMS EVALUATED
Key: R = reflector T= quartz tube S = UV source
MW lamp
▪ UV discharge bulb
▪ 9mm diameter bulb in elliptical reflector
cavity
▪ 1 back reflector opposing the source
▪ Air cooled via remote blower & exhaust
system
RadTech 2022, E. Nelson May 2022 10UV LAMP SYSTEMS EVALUATED
Key: R = reflector T= quartz tube S = UV source
MW lamp Planar LED lamp
▪ UV discharge bulb ▪ Planar arrangement
▪ 9mm diameter bulb in elliptical reflector ▪ 7x10 rows UV LED array
cavity ▪ 1 back reflector opposing the source
▪ 1 back reflector opposing the source ▪ Air cooled through integrated cooling
▪ Air cooled via remote blower & exhaust system
system
RadTech 2022, E. Nelson May 2022 11UV LAMP SYSTEMS EVALUATED
Key: R = reflector T= quartz tube S = UV source
MW lamp Planar LED lamp Multiple linear UV LED lamp
▪ UV discharge bulb ▪ Planar arrangement ▪ Linear arrangement
▪ 9mm diameter bulb in elliptical reflector ▪ 7x10 rows UV LED array ▪ 3 separate single row UV LED array
cavity fitted with focusing optics/reflector
▪ 1 back reflector opposing the source
▪ 1 back reflector opposing the source ▪ 3 back reflectors opposing each source
▪ Air cooled through integrated cooling
▪ Air cooled via remote blower & exhaust system ▪ Air cooled through integrated cooling
system system
RadTech 2022, E. Nelson May 2022 12IRRADIANCE MAPPING
Irradiance mapping within curing tube
RELATIVE INTENSITY MEASUREMENT
▪ Customized tool developed in-house to determine
the distribution of UV irradiance within the curing
tube
▪ Optical probe is coupled to a photodiode detector
that can capture the relative optical signal
3D Motion stage
▪ Probe collects diffuse radiation from all angles
▪ Allows validation and comparison of relative
intensities of various optical designs
Probe
Curing Tube
Data acquisition
RadTech 2022, E. Nelson May 2022 13IRRADIANCE MAPS
MW lamp
▪ Emission wavelength range 200-600nm
▪ Cannot compare relative intensity values
with LED lamps because of broad band
emission
▪ Shows distribution of UV
RadTech 2022, E. Nelson May 2022 14IRRADIANCE MAPS LED array
Reflector
Target Curing
Zone
Multiple linear array
MW lamp Planar LED array
▪ Emission wavelength 395nm
▪ Emission wavelength range 200-600nm ▪ Emission wavelength 395nm
▪ Highest uniformity at target
▪ Cannot compare relative intensity values
▪ Highest peak intensity at target
with LED lamps because of broad band
emission ▪ Relative peak intensity 4x planar LED system
▪ Shows distribution of UV
RadTech 2022, E. Nelson May 2022 15UNIFORMITY OF INTENSITY – OPTICAL SIMULATION
▪ Assume the fiber is a cylindrical cure target
▪ Uniformity the irradiation around the target perimeter
is important for consistent UV curing of the coating in
many applications
▪ By creating a small segmented cylinder around the
centre of the curing tube the intensity can be
calculated at each segment
▪ Use 360o positioning references to indicate location
of reflectors and UV sources
▪ Use radar graph to plot the intensity at each
segment
▪ Illustrates the direction and magnitude of light
striking the target
RadTech 2022, E. Nelson May 2022 16LED LAMP UNIFORMITY SIMULATIONS
▪ Using small back reflector ▪ Results shows uniformity of
▪ Deficiency of rays on the front more than 80%
increases intensity on backside
of the fiber ▪ Highest uniformity
of fiber
▪ Narrower 3x10 array shows
▪ Reduced intensity on the sides
reduced intensity on the sides
of the fiber
▪ 50-60% uniformity
RadTech 2022, E. Nelson May 2022 17ENERGY CONSUMPTION
UV lamp type Input Cooling Energy Consumption
UV discharge (MW) 60 Hz, 480VAC, 3ϕ Air 8.8 kW
Planar LED 60 Hz, 480VAC, 1ϕ Air 1.3 kW
Optimized linear LED 60 Hz, 480VAC, 1ϕ Air 1.1 kW
Each system operated at maximum power and power consumption measured
▪ LED lamps show significantly lower energy consumption than the MW lamp system
▪ Both LED systems had similar energy consumption values
▪ But deliver different levels of optical performance
▪ Optimized linear LED system shows:
▪ lowest energy consumption
▪ highest UV intensity
▪ best uniformity
RadTech 2022, E. Nelson May 2022 18CURE DATA
▪ Equipped a high draw speed tower (up to 3400 m/min) with UV LED lamp system
▪ Fully optimized linear array system
▪ Used commercially available coating formulated specifically for use with UV LED lamps (395nm)
▪ Used several inspection criteria to assess the degree of cure of the coating and if the coating met demanding performance
specifications
No. of lamps Degree of cure Stripping force Nd Result
(spec > 95%) (spec 1.0-5.0N) (spec > 20)
7 98.34 1.86 24.86 Pass
6 96.07 1.87 24.89 Pass
5 97.97 1.78 24.57 Pass
4 95.13 1.79 23.87 Pass
▪ Demonstrated that it was possible to meet the cure specification
✓ At high draw speed
✓ Using all UV LED
✓ Consuming less than 4.5 kW per line with 4x lamps
RadTech 2022, E. Nelson May 2022 19CONCLUSION ▪ Multiple linear LED system placed more of the photons in the active curing area compared to a planar LED system ▪ External optics can play an important role in improving the intensity of UV arriving at the cure target ▪ An optimized linear optical arrangement can provide high uniformity, high intensity and low power consumption ▪ Positive cure results of optical fiber coating can be achieved at high draw tower speeds with an optimized multiple linear system RadTech 2022, E. Nelson May 2022 20
THANK YOU!
DISCLAIMER This presentation including all its parts (e.g. photographs, diagrams, drawings etc.) is protected by copyright. Any exploitation outside the close limits of the Copyright Act is inadmissible and punishable, unless pre-approved by Heraeus. This applies in particular to photocopies, publications, translations as well as storage and processing in electronic systems. All data in this presentation were thoroughly ascertained by Heraeus. However, Heraeus does not assume any liability for their correctness or completeness.The data are based on conditions of use and environmental influences assumed by Heraeus. They cannot be adopted indiscriminately, but require prior verification for the respective use of the customer. Exclusively Heraeus‘ General Terms of Delivery shall apply to all deliveries of Heraeus for commercial transactions with business enterprises. RadTech 2022, E. Nelson May 2022 22
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