End Capped HighPower Assemblies

Fiberguide’s end capped fiber optic assemblies allow the user to achieve higher coupledpower into a fiber core by reducing the power density at the air/ silica interface, commonly
the point of laser damage. End cap diameters and lengths are offered for select numericalapertures and fiber cores size, but can be easily customized for a variety of fiber types andspecialized applications.
GENERAL SPECIFICATIONS:• Standard Fiber Type: Step Index Multimode Core Sizes, 50μm - 400μm
Other fiber types (e.g., singlemode, graded index) available upon request.
• Wavelengths: 190nm – 1250nm (High OH) / 300nm – 2400nm (low OH)• Standard Numerical Aperture: 0.20 or 0.22 Std• Connector Options: High Power SMA, High Power FD-80• Sheathing Options: PVC Coated Stainless Steel Monocoil, Bare Stainless Steel Monocoil• Power Handling Capacity: Up to 3 kW, depending on fiber size and laser specifications• Standard Temperature Range: -40°C to +100°C (-40°F to +212°F)
FEATURES & BENEFITS• End capped assemblies allow for muchhigher transmitted powers by reducing thepower density to a level below the damage
threshold• Shaped endcap tips can be tailored to
specific laser launch conditions andapplications• High Power SMA and D-80 compatible
connector options offer superior thermal
management while minimizing connector
stress for NA conservation• Epoxy free cantilevered nose design(available in select versions) minimize laserand heat damage to surrounding materials• Fiberguide’s proprietary laser polishingprocess minimizes surface imperfections,and maximizes power handling
Headquarters & Fiber Manufacturing

Assembly & Manufacturing Facility

1 Bay Street, Stirling, New Jersey 07980
Phone: (908) 647-6601
SPEC 721 017 Rev. 01/20/14

3409 E. Linden St., Caldwell, Idaho 83605
Phone: (208) 454-1988
page 1 of 6Contact Us
Email: info@fiberguide.com
www.fiberguide.com
Store.fiberguide.com

End Capped HighPower Assemblies
SPECIFICATIONS:
Optical Fiber Type

Step Index Multimode. (End Capping onto other fibers types
available upon request)

Std Fiber Core Dia.

50µm to 400µm

Fiber Jacket Options

Nylon, Acrylate, Tezel, Polyimide

Numerical Aperture(NA)

0.20 ±0.02 (23° Full Acceptance Angle)
0.22 ±0.02 (25° Full Acceptance Angle)

OperatingWavelength (λ)λ = 190nm - 1250nm (Ultraviolet - Visible)
λ = 300nm - 2400nm (Visible - Infrared)

Typ Temperature
Range-40°C to 100°C / -40°F to 212°F (fiber coating dependent)

0.20 Numerical Aperture Fiber
Fiber Core Size(µm)

Endcap
Diameter (µm)

Nominal Endcap
Length (mm)Endcap Length
Tolerance (µm)

100200
300
400

300
600
900
1200

0.57
1.13
1.70
2.27± 16± 23± 34± 45

0.22 Numerical Aperture Fiber
Fiber Core Size(µm)

Endcap
Diameter (µm)

Nominal Endcap
Length (mm)Endcap Length
Tolerance (µm)

100200300
400300600
900
1200

0.52
1.03
1.55
2.06± 15± 21± 31± 41

Headquarters & Fiber Manufacturing

Assembly & Manufacturing Facility

1 Bay Street, Stirling, New Jersey 07980
Phone: (908) 647-6601
SPEC 721 017 Rev. 01/20/14

3409 E. Linden St., Caldwell, Idaho 83605
Phone: (208) 454-1988
page 2 of 6Contact Us
Email: info@fiberguide.com
www.fiberguide.com
Store.fiberguide.com

End Capped HighPower Assemblies
General Design Considerations and Guidelines
When selecting optical cable assemblies for power delivery systems, designers must consider
the power limitations of the three main components of the cable assembly: the base material,
the input connector, and the mode stripper (if applicable).
The first consideration is the base material, more specifically the base material interface.
Fiberguide’s high power assemblies are built with our Step Index Multimode fiber. This fiber
has a pure fused silica core and fluorine doped cladding. The fused silica is extremely highpurity and, as a result, can handle enormous amounts of optical energy. The challenge,
however, is getting the optical energy into the fused silica, and this is governed by the air-silica
interface that exists at the input connector. Fiberguide uses a proprietary laser polishingtechnique to maximize the amount of power that this interface can handle.
The failure mode for Continuous Wave (CW) Lasers is thermal, caused by microscopic
irregularities in the air-silica interface absorbing the laser’s energy. For Pulsed Lasers, thefailure mode can either be thermal or a dielectric breakdown at the atomic level, depending on
the laser’s characteristics. In either case, there is a maximum power per unit of area, referred
to as the damage threshold, that can be coupled into the assembly. This is expressed in W/cm2(irradiance) for CW lasers and J/cm2 (fluence) for Pulsed Lasers. The reason for this differenceis that Pulsed Lasers operate as a series of repeating energy bursts, or pulses. The duration ofthe pulses and their repetition rate determine the Peak Power and Average Power for thelaser. Since a Joule (J) is the amount of energy required to produce one Watt (W) of power for
one second, this unit of measure is used to remove the time factor so comparisons can beeasily made.
Determining if a laser will damage a fiber involves calculating the irradiance or fluence for thelaser by dividing the CW Power, or the Energy per Pulse, by the area of the beam where it
makes contact with the fiber. This value must be adjusted to compensate for wavelength in aCW laser, and wavelength and pulse duration in a Pulsed Laser. If the adjusted value is below
the damage threshold, the beam size and fiber size are suitable for the laser. If the adjustedvalue exceeds the damage threshold, the beam size and / or the fiber size should be increased
until the irradiance or fluence is below the damage threshold. The charts and tables on thefollowing pages show maximum irradiance and fluence values for various fiber core sizes by
wavelength for CW lasers, and by wavelength and pulse duration for Pulsed Lasers.
The power handling capabilities for the other two main cable assembly components - the input
connector and a mode stripper, if applicable, must also be examined. The failure mode onthese is always thermal and there are detailed sections on each of these components in thefollowing pages.

Headquarters & Fiber Manufacturing

Assembly & Manufacturing Facility

1 Bay Street, Stirling, New Jersey 07980
Phone: (908) 647-6601
SPEC 721 017 Rev. 01/20/14

3409 E. Linden St., Caldwell, Idaho 83605
Phone: (208) 454-1988
page 3 of 6Contact Us
Email: info@fiberguide.com
www.fiberguide.com
Store.fiberguide.com

End Capped HighPower Assemblies
Table 1: Background & Assumptions
CW Air-Silica Fused
Interface Damage
Threshold~1.5 MW/cm2 (CW Laser @ λ: 1064nm)Damage Threshold is λ dependent, and behaves relatively linearly in the range
from 190nm - 2400nm with the shorter wavelengths being more destructive.

~16.0 J/cm2 (Pulsed Laser @ λ: 1064nm and τ: 1ns)
Damage Threshold is λ dependent, and behaves relatively linearly in the range
from 190nm - 2400nm with the shorter wavelengths being more destructive.

Pulsed Air-Fused
Silica Interface
Damage Threshold

Damage Threshold is τ dependent, and scales with the square root of thepulse duration from 10ps to 1µs with the shorter pulse durations being moredestructive.
NOTE: The CW and Pulsed Air-Fused Silica Interface Damage Thresholds above
have been adjusted to compensate for the peak intensity in the Gaussian
Beam Profile.

Spot Size Diameter≤ 85% of the Fiber Core Diameter

Alignment & BeamWaist

X & Y Alignment within ± 5% of the core diameter / Z Position beyond source
beam waist

Numerical
Aperture (NA)Fiber NA ≥ Source NA + 10%

Beam Shape &Quality

The spatial profile and quality of the beam will greatly affect high power
performance. This analysis assumes a Gaussian Beam where the peak fluenceis given by “2 E/p*( Wo)2“, meaning that the peak power is approximately
double the 1/e2 specified power.

Connector Polish,End Face, &Flatness

The connector end face must be factory laser polished to reduce microscopic
inclusions and be cleaned prior to use. The end face must also be flat, <10% of
the core diameter peak to valley, so it doesn’t act like a lens and focus thelaser energy inside the fiber.

AR Coating

When AR Coatings are applied to optical fibers, the coating may become thelimiting factor to power handling capability, so it is important to check thespecifics of the selected coating. For high power applications, AR coating istypically not recommended.

Please Note: This information provided is designed to help guide product selection, because each opticalsystem is unique, Fiberguide strongly recommends thorough testing before committing to system criticalcomponents.

Headquarters & Fiber Manufacturing

Assembly & Manufacturing Facility

1 Bay Street, Stirling, New Jersey 07980
Phone: (908) 647-6601
SPEC 721 017 Rev. 01/20/14

3409 E. Linden St., Caldwell, Idaho 83605
Phone: (208) 454-1988
page 4 of 6Contact Us
Email: info@fiberguide.com
www.fiberguide.com
Store.fiberguide.com

End Capped HighPower Assemblies
Maximum CW Power Level Table:
The following table shows CW Power Maximums. For fiber sizes ≤ 400μm, the air-silica
interface damage threshold is more commonly the limiting factor for the assembly. For larger
core sizes, the connector power limits typically govern the overall power handling capabilitiesof the assembly. Please note that In order to illustrate the dependency of damage thresholdon wavelength, the table shows power levels that are far beyond what is possible / currently
available for some wavelengths.
Table 2: CW Power Maximums for End capped Fiber Core Sizes 100μm - 400μm with λ: 193nm - 2100nm

Wavelength

Fiber Core
Size (μm)

193nm

405nm

532nm

808nm

980nm

1064nm1900nm

2100nm

100
200
300
400

45
186
417
741

96
490
876
1554

129
510
1149
2043

195
777
1742
3102

234
942
2108
3762

255
1020
2286
4086

456
1824
4104
7296

489
2016
4536
8064

Pulsed Lasers
When determining power limits for cable assemblies coupled to Pulsed Lasers, the Pulse
Duration (τ) dictates which calculations are used. For Pulse Durations greater than 1
microsecond: 1μs (10-6 s), the failure mode is thermal, and the CW calculations / charts alone
are used. In this case, the Laser’s Average Power = Energy Per Pulse (J) x Pulse Frequency (Hz), isused in place of the CW power. For Pulse Durations smaller than 10 picoseconds: 10ps (10-11 s),
the failure mode is 2nd order, non-linear phenomenon, such as Stimulated Brillion Scattering(SBS) or Stimulated Raman Scattering (SRS), which are always present in optical fiber andbecome dominant actors at very short pulse durations. In these cases, thorough testing ofvarious beam and / or fiber sizes is the best way to determine what is appropriate.
For pulse durations between 10ps and 1μs, the failure mode tends to be a dielectric breakdown
at the atomic level, and the Energy Per Pulse and the Fiber Size are the key factors indetermining power maximums. To determine if a fiber size is suitable, the Energy per Pulse must
be divided by the area of the beam where it makes contact with the fiber and the resulting
number compared to the air-silica damage threshold. This is straightforward if the laser
characteristics match those of the damage threshold, and an additional step is required if theydo not.
In cases where the wavelength and/or pulse duration of the laser are different than those of thedamage threshold (λ: 1064nm and τ: 1ns), Table 3 (next page) is used to determine thecorrection factor. The Energy Per Pulse of the laser is then multiplied by the correction factor tocalculate the Equivalent Energy Per Pulse at λ: 1064nm and τ: 1ns. These are derived by scalingwavelength in a linear fashion where the shorter wavelengths are more destructive, and byscaling pulse duration in a square root fashion where the shorter pulses are more destructive.
Headquarters & Fiber Manufacturing

Assembly & Manufacturing Facility

1 Bay Street, Stirling, New Jersey 07980
Phone: (908) 647-6601
SPEC 721 017 Rev. 01/20/14

3409 E. Linden St., Caldwell, Idaho 83605
Phone: (208) 454-1988
page 5 of 6Contact Us
Email: info@fiberguide.com
www.fiberguide.com
Store.fiberguide.com

End Capped HighPower Assemblies
Pulsed Lasers (cont’d)Once the Equivalent Energy per Pulse at λ: 1064nm and τ: 1ns is known, Table 4 (next page) canbe used to determine which fiber size(s) can potentially be used. These maximums are based on
the assumptions stated in Table 1 in the previous section.
The final step for Pulsed Lasers is to also check the Laser’s Average Power using the CW
calculations / chart to take the duty cycle into consideration, where Average Power = Energy Per
Pulse (J) x Pulse Frequency (Hz). All potential fiber sizes from the previous step must be
evaluated to ensure they pass both criteria. These are ultimately the fiber sizes that can be usedwith a given Pulsed Laser Source.
Table 3: Correction Factors used to Convert Energy Per Pulse toEquivalent Energy Per Pulse at λ: 1064nm and τ: 1ns

Wavelength (nm)(Sec)

λ: 193nm

λ: 405nm

λ: 532nm

λ: 808nm

λ: 980nm

10ps
50ps
100ps
500ps
1ns
5ns
10ns
50ns
100ns
500ns
1µs

55.13
24.65
17.43
7.80
5.51
2.47
1.74
0.78
0.55
0.25
0.17

26.27
11.75
8.31
3.72
2.63
1.17
0.83
0.37
0.26
0.12
0.0820.00
8.94
6.32
2.83
2.00
0.89
0.632
0.28
0.20
0.09
0.06

13.17
5.89
4.16
1.86
1.32
0.59
0.42
0.19
0.13
0.06
0.04

10.86
4.86
3.43
1.54
1.09
0.49
0.34
0.15
0.11
0.05
0.03

λ:
1064nm
10.00
4.47
3.16
1.41
1.00
0.45
0.32
0.14
0.10
0.04
0.03

λ:
1900nm
5.60
2.50
1.77
0.79
0.56
0.25
0.18
0.08
0.06
0.03
0.02

λ:
2100nm
5.07
2.27
1.60
0.72
0.51
0.23
0.16
0.07
0.05
0.02
0.02

Table 4: End Capped Maximum Energy Per Pulse (mJ) at λ: 1064nm and τ: 1ns

Fiber Core Diameter
Maximum Equivalent
Energy Per Pulse (mJ)

100µm

200µm

300 µm

400 µm

2.7

10.8

24.3

43.5

Headquarters & Fiber Manufacturing

Assembly & Manufacturing Facility

1 Bay Street, Stirling, New Jersey 07980
Phone: (908) 647-6601
SPEC 721 017 Rev. 01/20/14

3409 E. Linden St., Caldwell, Idaho 83605
Phone: (208) 454-1988
page 6 of 6

Contact Us
Email: info@fiberguide.com
www.fiberguide.com
Store.fiberguide.com