WS@ECOC2015– How should we design optical communication networks with flexible DSP based transceivers? Organizers Benn Thomsen UCL, UK Massimiliano Salsi Juniper Networks, USA Title: Vincent A.J.M. Sleiffer Omron Europe B.V., Netherlands Low-loss hollow-core photonic bandgap fibers: Implications for system design and DSP

1. Low loss hollow core optical fibers:
Implications for system design and DSP
V.A.J.M. (Vincent) Sleiffer
ECOC 2015, Valencia, Sept 27th – Oct 1st
Sunday 27 Sept, WS: How should we…?, Room Malvarossa, 16:00 - 18:00

3. Why hollow core photonic band gap fibers?
Optical signal mainly propagates in air rather
than glass (SiO2), resulting in three main
benefits:
Virtually no nonlinear distortion
Ultra low Rayleigh scattering, potential for
ultra low loss transmission medium (@ 2 μm)
neff close to 1, resulting in a ~1.5 μs/km
latency reduction compared to glass fibers
Try to achieve propagation of the optical
signal in air as much as possible!

4. Ultimate low loss of HCF
• Mode field overlap with cladding increases moving
longer wavelengths. Ultimately infrared absorption
limited.
Depending on fraction
optical signal travelling
in air!
P.J. Roberts et al., “Ultimate low loss of hollow-core photonic crystal
fibres”, in Opt. Exp., Vol. 13, No. 1, pp. 236-244 (2005).

5. Ultimate low loss of HCF
F. Poletti et al., “Hollow-core photonic bandgap fibers: technology and
applications”, in Nanophotonics, Vol. 2, No. 5-6, pp. 315-340 (2013).
• Reduction of optical field overlap with cladding by
removing more cells for lower loss. Multi-mode!

6. Single mode transmission challenges
(@ 1550nm)
• Large analogy with current transmission systems
– Same technology for transmitters, receivers,
amplifiers, and WSS/ROADMs can be employed
• Big differences
– Fiber loss has to be solved
– No non-linear compensation required!
– Mode-field diameter mismatch
– Impulse response?

7. Single-mode transmission – Impulse
response (@ 1550 nm)
Th.1.2.4 • 10:00-10:15: Maxim Kuschnerov et al., “Data Transmission through up
to 74.8 km of Hollow-Core Fiber with Coherent and Direct-Detect Transceivers”
-1230 -820 -410 0 410 820 1230
-60
-40
-20
0
Tap number
Magnitude[dB]
7 Loops (43.4 km)
3 Loops (18.2 km)
1 Loop (6.2 km)
128Gb/s DP-QPSK
Modal crosstalk increases impulse response

8. Single mode transmission challenges
• Control modal coupling
• Chromatic dispersion?
• Fiber robustness
• Splicing (low loss/MPI)
Y. Chen et al., “Multi-kilometer Long, Longitudinally
Uniform Hollow Core Photonic Bandgap Fibers for
Broadband Low Latency Data Transmission”, in JLT,
Early Access article (2015).
J.P. Wooler et al., “Robust Low Loss Splicing of Hollow
Core Photonic Bandgap Fiber to Itself”, in Proc. OFC,
paper OM3I.5 (2013).

9. Single mode, short distance transmission
• Low latency short distance transmission using
commercial coherent 100G DP-QPSK with latency
optimized FEC over 2.75km HCF demonstrated.
– Primitive FEC used to handle mode crosstalk
• M. Kuschnerov et al., “Transmission of Commercial Low Latency Interfaces
over Hollow-Core Fiber”, in JLT, Early Access article (2015).

10. Few-mode transmission challenges
(@ 1550nm)
• Large analogy with demonstrated few-mode
systems
– Same technology for transmitters, spatial
multiplexers, receivers, (few-mode) amplifiers, and
WSS/ROADMs can be employed
• Big differences (additional to single mode)
– Modal differential group delay (~factor 100 larger
than solid-core FMF)
– Mode-dependent loss (factor 2 between fundamental
and higher-order mode, due to larger overlap with
glass interface)

11. Few-mode transmission (@ 1550 nm)
• 310m 37-cell HC-PBGF
V.A.J.M. Sleiffer et al., “High Capacity Mode-Division Multiplexed
Optical Transmission in a Novel 37-cell Hollow-Core Photonic Bandgap
Fiber”, in JLT, Vol. 32, No. 4, pp. 854-863 (2013).

12. Few-mode transmission (@ 1550 nm)
• Mode-dependent loss

13. Few-mode transmission (@ 1550 nm)
• Large differential mode delay and unwanted
coupling to other modes.

14. Challenges at new transmission window
(@ 2 μm)
• New optical components required
– Lasers
– Modulators
– Coherent receivers
– WDM couplers
– Isolators, circulators
– WSS/ROADMs
– Spectrum analysers

15. Challenges @2 μm transmission window
• Thulium-doped fiber amplifier (S/C/L band)
– Analog with (FM-)EDFA but larger window (1700-2100 nm (30 THz) vs
1480-1610 nm (15 THz))
Z. Li et al., “Diode-pumped wideband thulium-doped fiber amplifiers
for optical communications in the 1800 – 2050 nm window”, in Opt.
Exp., Vol. 21, No. 22, pp. 26450-55 (2013).

16. Questions?
F. Poletti et al., “Hollow-core photonic bandgap fibers: technology and
applications”, in Nanophotonics, Vol. 2, No. 5-6, pp. 315-340 (2013).