Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of...

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Tech Breakfast: Fibre Optic Multiplexing CWDM & DWDM [email protected] @IsItBroke on Twitter http://www.root6.com/author/phil

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Page 1: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Tech Breakfast: Fibre Optic Multiplexing

CWDM & DWDM

[email protected] @IsItBroke on Twitter http://www.root6.com/author/phil

Page 2: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Long range fibre optic cabling

• Single mode vs. Multi mode – fundamentally different. • CWDM vs DWDM • Campus-wide connectivity • Facility – DC connectivity • Outside Broadcast – SMPTE optical triax • Facility – Facility connectivity; the Dolby 4k project

Page 3: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Single mode vs. multi mode cable• Single mode cable (“OS1” / “OS2” or “9µ/125µ”) is the original style of fibre

optic cable developed by BT and Corning in the 1970s • With a nine micron transmissive core the cable is able to contain the 1270 –

1690nm wavelengths efficiently.

V = number of modes k0 = wave number a = core’s radius (9µ vs. 50µ) n1 & n2 = refractive indices

Page 4: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

The cheap ‘n’ cheerful young pretender – Multi mode

• Whereas single-mode contains the light wave near-perfectly multi-mode cable relies on total internal reflection; the wavefront bounces down the fibre core as it hits the core/cladding interface.

• By clever use of interference modes many distinct waves can be launched down the cable and by using an interference detector laser-diode the modes can be recovered. All at 850nm typically.

• Limitations are length – 500 – 1,500m typically • Graded index fibre OM4 is the newest standard.

Page 5: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Limitations of multi-mode optics

• Distance – due to “modal-dispersion” • Distances typically range from 150 – 650m (depending on

application) and can be calculated using the bandwidth-loss product. 10Gbits-1; typical max data rate in 2017.

• Graded Index OM4 fibre uses a transmissive core that varies it’s refractive-index across the diameter of the core so that the wavefront is better guided down the core.

Page 6: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

The better technology – single mode fibre.

• In many ways very similar to multi-mode technology, same connectors, style of patch panel, cable construction etc.

• Works in an entirely different way – light is optimally constrained in a 9µ transmissive core so no need for total-internal-reflection with problems of modal dispersion etc.

• MUCH higher data rates and distances (80km without amplification)

• MUCH better signal-to-noise ratio; 28dBs with best optics. • Wider application in video and data. • Multiplexing is possible – more of that in the next session.

Page 7: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

What happens if we don’t have enough fibre?

• Single mode fibre is by definition a long range technology and so it may be hard to put in more.

• Internal IT dept may have control over fibre network • Metro networks may cross local authority boundaries • Wouldn’t it be great to be able to stack many signals onto a fibre? • The two technologies are CWDM and DWDM

Page 8: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

CWDM – Course Wave Division Multiplexing• 8/16/18 optical channels • Centre wavelengths according to ITU-T G.694.2 • Channel centre wavelength 1270~1610nm • Channel clear passband ITU+/-7 nm • Insertion loss 8ch-2.5dBm, 16ch-3.5dBm (max) • Passband ripple 0.5dBm (max) • Adjacent channel isolation 30dBm (min) • Non-adjacent channel isolation 45dBm (min) • Return loss 45dBm (min) • Operating temperature range 0 to +70C • Maximum power handling 300mW

Page 9: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

How does the technology work?

A combination of tuned SFP modules and optical engineering

Page 10: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

And which engineer doesn’t take the lid off?!•All the filtered wavelengths go via dichroic elements that filter around that particular band. •The common optic is the other side of a combining element. •A good way to think of this is a prism.Well, nearly…!

Page 11: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

CWDM SFPs

Page 12: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

CWDM SFPs

• Most SFPs are transceivers – they send and receive data

• Their outputs are set for a tuned wavelength • They are colour-blind on their inputs • For passive CWDM systems the multiplexer does

not care what is an input and what is an output; Ethernet is the example.

• The optics are the only limit on each λ’s bandwidth.

Page 13: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

CWDM SFPs

Typical distribution of wavelengths – so go up the fibre, some come back.

Page 14: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Show & Tell

• A quick demo of BarnFind’s CWDM system • Standard MSA-compliant SFP & SFP-ports • 3G video going up and down a fibre (twice!) • BarnStudio – Barnfind’s management software • Integrates with numerous router panels (BM etc)

Page 15: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Proper money - DWDM• CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm

(50Ghz grid) • This means you can achieve 96/192 channel/fibre • 1,000km without amplification (vs. 80km for CWDM) • However, signals are single direction. • Erbium Doped Fibre Amplifier uses a pump laser to bring up

electrons to a higher energy level, amplification is achieved by emitted photons of the same signal wavelength with the help of stimulated emission.

Page 16: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Expensive

• Unlike passive CWDM parts everything relies on calibrated lasers

• Transatlantic fibres (first TAT-8 in 1988) had limited bandwidth, but in 1996 TAT-12 used EDFA along it’s route to carry DWDM traffic.

• Between buildings in London it’s almost always cheaper to buy more cores and continue with CWDM

• You can exploit the 2nd core that ISPs always provide.

Page 17: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Outside Broadcast camera – optical triax

• SMPTE camera cables are expensive; typ. >£1k

Page 18: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Dolby 4k remote grading network

• To allow numerous Soho facilities to control different grading machines from Dolby grading rooms.

• No compression • No latency • 4K and HDR (of whatever flavour) • Remote management interface to allow control of the end-

points • As ever expense is an issue from an equipment and ongoing

cost POV

Page 19: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

A variety of applications• Baselight• Resolve• AN Other grading machine

Each have their own control panel requirements which aren’t easily extended over distance.

UHD/4K – late 2016 (and probably still the case a year later) demands quad-link 3G SDi

(If anyone mentions “doing it over IP” they can leave now!)

Page 20: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Fibre around Soho

There is now sufficient fibre under W1 that the cost of going point-point (or via Volta etc.) is not onerous.Being IT-based EU-Networks etc. provide a duplex pair of single-mode fibres which serves us well for backup as we really only need one core for;

•4 x 3G SDi •3 x Gigabit Ethernet•3 x KVM signal type (when using a non-Baselight config.)

Page 21: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Specific configuration

Three networks are necessary;

1.Baselight host control – PXE boot from remote Baselight machine 2.Dolby CMU control – for PQ HDR workflows 3.Barnfind management console so Ian & Ady can keep an eye on things…!

Page 22: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Further reading

https://www.barnfind.no/downloads

Barnguide v 2.8 – everything you need to know!

http://www.root6.com/blog

All things relating to facilities engineering.

Page 23: Tech Breakfast: Fibre Optic Multiplexing · Proper money - DWDM • CWDM has a channel spacing of 20nm • DWDM by contrast uses 0.8nm (100Ghz grid) or 0.4nm (50Ghz grid) • This

Thank-You!

[email protected] @IsItBroke on Twitter http://www.root6.com/author/phil