FSO with RF Protection for Carrier-Class All-Weather Broadband Wireless Links

May 2004R.T. Carlson, Ph.D. CTO, fSONA Communications Corp

The SONAbeam™ Advantage - Superior Quality. Premium Reliability.

Superior Design; Rigorous Qualification Military/carrier-grade with 15 year product lifetime

System test –40C to 60C; Subsystem test -50C to 85C

Telcordia (Bellcore) standards-based design and test

Engineered for High-Rel 24/7 Operations Electronics operate only 10°C above ambient: low-stress

Subsystems >200 yr MTBF. Telecom-grade power.

20-40 times more laser power than other FSO systems

Adaptive laser power control operates laser at low power in clear weather for low stress and enhanced reliability

Superior Environmental Capabilities Completely sealed housing (tested submerged

underwater)

Cast aluminum housing with rigid multi-point attachment

Precision pointing in 120km/hr wind; survive >160 km/hr

Lasers actively cooled to 25°C, even in desert conditions

Dual/Quad Transmitter Redundancy Multiple redundant and independent lasers, laser

drivers, laser coolers, & cooler controllers

SONAbeam -S

SONAbeam -M

SONAbeam FSO Attenuation in Heavy Rain: - much less than at EHF frequencies

Rain Attenuation – ITU Rain Zone K

‘One Size Fits All’ for all the U.S. (except the Gulf Coast1)5-9s Rain Availability1

(5 min outage/yr)

100 mm/hrFSO:

20 dB/km3

60-90 GHz:

36 dB/km2

4-9s Rain Availability

(1 hr outage/yr)

42 mm/hrFSO: 8 dB/km 60-90 GHz:

18 dB/km2

1. 5-9s rain rate for Region K is same as 4-9s for Gulf Coast, Region N

2. FCC Bulletin No.70, 33 dB/km; experimental data indicate higher rain atten

3. SONAbeam rain performance validated in Costa Rica, rain region P, to 135 mm/hr

SONAbeam link in multi-hour intense rain: Example below: 50-100 mm/hr, 900m link

loss of link

8 Oct 2002, 11:00 to 24:00

-33

-30

-27

-24

-21

-18

-15

-12

-9

-6

-3

0

Tim e (hrs :m in:s ec)

Rx

Po

wer

(d

Bm

)

SONAbeam Extreme Rain Performance Summary(900m Test in Costa Rica - ITU Rain Region P)

»Calibrated rain gauge measured rain rates up to 180 mm/hr

»Only 1 rain outage: 3.5 min in very extreme 156-180 mm/hr rain.

»Heaviest rain events:

Date Max Rate Time Link Status Margin

14 Sept 120 mm/hr 15:26 Link Up 10 dB

17 Sept 120 mm/hr 13:03 Link Up 3 dB

25 Sept 132 mm/hr 15:33 Link Up 3 dB

28 Sept 96 mm/hr 16:21 Link Up 12 dB

1 Oct 180 mm/hr 13:36 Down 3.5 min 0 dB

6 Oct 96 mm/hr 11:18 Link Up 12 dB8 Oct 96 mm/hr 16:32 Link Up 10 dB

»SONAbeam rain-performance model has been validated for extreme rain rates of up to 132 mm/hr.

NOAA: Number of days/year moderate to heavy fog occurs with visibility < 400m

Example of Costa Rica Tests – 900m Link Fog Outages

A few fog events caused 900m link outages.

All of the fog outages were very late at night, midnight to 4 AM.

Late-night fog outages:

Date Time Period Fog Outage

16 Sept 2 AM 38 minutes

21 Sept Midnight 22 minutes

22 Sept 3 AM 15 minutes

23 Sept 12 and 2 AM 100 minutes

30 Sept 4 AM 20 minutes

Fog outages were rare, and occurred at hours not an issue for business services or non-emergency applications.

Limitations to EHF as Stand-alone Links

»60-90 GHz frequencies have very severe rain-fade attenuation.

»74/84 GHz frequency bands will be point-to-point licensed; Licensing puts constraints on competing service providers.

»While interference is mitigated at EHF, it is not eliminated (especially at hubs). Hence, 74/84 GHz licensing to mitigate interference issues.

»BER is impacted by dispersion due to multiple scattering in rain. This is often overlooked in rain performance projections, with just rain attenuation used in calculations.

»Pointing wander is a well-known phenomenon at EHF frequencies due to refractive index variations, especially early morning and evening. Also antenna oscillation in wind gusts with large, high-gain antennas

»But 60 GHz and 74/84 GHz represent an ideal EHF solution to complement FSO, with fallback to RF in heavy fog conditions.

Protected Links with FSO and RF

We address here very broadband point-to-point wireless transmission for backbone links, spurs, and premium access: OC-12, Gigabit Ethernet, and OC-48

Protected, all-weather links are essential at >OC-12 bandwidth

Fully 1:1 redundant, with automatic fail-over

Required for SLAs with fiber-quality assurance

Rather than ‘which technology?’, the best solution is both: FSO and RF are complementary broadband wireless technologies for

heavy rain & fog penetration

Carrier studies have concluded that the equipment cost of protected FSO/RF is not a significant cost factor for OC-12 and greater bandwidths

fSONA 1000 meter test range: SONAbeam/EHF Protected Link, GigE

Architecture of Protected FSO/RF Link: Indoor Rack-mount SONAswitch APS

SONAswitch APS for RF Protection of SONAbeam FSO Links (DS-3 to OC-48; 45-2500 Mbps)

SONAswitch APS - Graphical User Interface

SONAswitch APS - Hitless Switching Example

7:42:09 As fog increased, rcv signal fell below APC threshold

Adaptive power control (APC) increased lasers to max output power

7:43:55 Fog became worse; rcv signal fell below switching threshold

Alarm posted: APS switched to RF backup. 4 CRC errors = 9µ sec switching

7:57:39 Fog thins: rcv signal exceeded threshold to switch back

Alarm cleared: APS switched back to SONAbeam. 7 CRC errors

8:01:26 Another patch of fog before fog cleared

Alarm posted: APS switched to RF backup. 7CRC errors = 15µ sec switching

1000m Testbed in Light Fog - May 11, 2004

Three protection-switching events due to fog:

- First: RF active for 13.75 minutes

- Second: RF active for 0.5 minute

- Third: RF active for 0.3 minute

Total of 36 GigE frames impacted by these six protection-switching/switchback events. (2.2 µ sec per per 256-byte frame)

SONAswitch APS switching time < 15 microsec

3000x faster than SONET APS spec (50 millisec)

Summary of SONAswitch APS Results: Protection Switching in 15 microsec

Gigabit Ethernet FSO with RF Protection – New installation in Wash. DC area

Installation and link commissioning, May 17-20:

910 meter FSO/RF-protected link in Falls Church, VA

For a U.S. Gov’t. organization as proof-of-concept testbed

SONAbeam 1250-M with 60 GHz RF backup

Gigabit Ethernet test set, 1250 Mbps full-duplex, 256-byte frames, 100% utilization (450,000 frames/sec)

SONAswitch for automatic protection switching and log files

Expectations for 850m Wash DC Testbed

Expect to achieve annual link availability of 1.000000

Protected link provides redundancy for high-rel requirements

FSO and EHF are complementary broadband technologies, employed for all-weather link operation:

Expect FSO up circa 99.9%, with RF backup active circa 0.1%

FSO down in heavy fog, with link running on RF protection

RF down, FSO up in heavy rain - incl. 100 mm/hr thunderstorms

RF down in wet snow, FSO up in worst snowstorms

Protected Broadband Wireless Solution- using complementary SONAbeam & EHF technologies

Protected Gigabit Ethernet or OC-12 LinkSONAbeam 1250-M with SONAswitch APS and 60 GHz RF (10 dBm, 24” antenna)

ITU Rain Region 5-9s Rain,

mm/hr

60 GHz range,

rain

60 GHz range,

fog

SONAbeam

range, rain

All-weatherProtected

Link Range

D: Seattle, Portland OR, San Francisco, Vancouver BC

42 950 m 1500 m 2200 m 1500 m

E: San Diego, Los Angeles, LasVegas, Phoenix, Denver

70 800 m 1500 m 1500 m 1500 m

K: Boston to Wash DC, Chicago all of central and eastern U.S.

100 700 m 1500 m 1200 m 1200m

M: Atlanta, Dallas, Florida

120 600 m 1500 m 1050 m 1050 m

SONAbeam 2500-M for OC-48 Apps

Over the past nine months fSONA built and tested a 2.5 Gbps (OC-48) system using our proven 1550nm InGaAs semiconductor laser and APD technology

4 links built: two links for delivery to a U.S. Govt. agency

Government acceptance tests performed April 11, 2004.

Tests performed on fSONA 5000 meter rooftop test range

Acceptance test results, SONAbeam 2500-M:

5 km FastE test, 20 minutes, no packet errors

5 km OC-3 test, 20 minutes, zero bit errors

5 km OC-12 test, 20 minutes, zero bit errors

5 km GigE test, 20 mnutes, no packet errors

5 km OC-48 test, 20 minutes, zero bit errors

Summary and Conclusions

FSO and RF technologies are complementary and very well suited for protection of each other (SONAbeam up in heavy rain; RF up in heavy fog)

SONAbeam GigE FSO successfully demonstrated on 1000m test range with 60 GHz EHF backup link

SONAswitch APS provides hitless protection switching 3000 times faster than SONET APS spec

U.S. govt. agency performed acceptance test of 2.5 Gbps SONAbeam 2500-M, April 2004.

Protected links with 2.5 Gbps SONAbeam and 74/84 GHz radio are projected for future apps.

Get connected !Get connected !