363-206-295
About This Document
xliv
Issue 1
December 1997
Conventional lasers can produce an intense beam of monochromatic light. The
term monochromaticity means a single wavelength output of pure color that may
be visible or invisible to the eye. A conventional laser produces a small-size beam
of light, and because the beam size is small the power density (also called
irradiance) is very high. Consequently, lasers and laser products are subject to
federal and applicable state regulations as well as international standards for their
safe operation.
A conventional laser beam expands very little over distance or is said to be very
well collimated. Thus, conventional laser irradiance remains relatively constant
over distance. However, lasers used in lightwave systems have a large beam
divergence, typically 10 to 20 degrees. Here, irradiance obeys the inverse square
law (doubling the distance reduces the irradiance by a factor of 4) and rapidly
decreases over distance.
Lasers and Eye Damage
Light energy emitted by laser and high-radiance LEDs in the 400-1400nm range
may cause eye damage if absorbed by the retina. When a beam of light enters the
eye, the eye magnifies and focuses the energy, magnifying the irradiance. The
irradiance of energy that reaches the retina is approximately 10
5
or100,000 times
that at the cornea; and if sufficiently intense, may cause a retinal burn.
The damage mechanism at the wavelengths used in telecommunications is
thermal in origin (that is, damage caused by heating). Therefore, a specific
amount of energy is required for a definite time to heat an area of retinal tissue.
Damage is not instantaneous. It occurs only when one looks at the light
sufficiently long that the product of the retinal irradiance and the viewing time
exceeds the damage threshold. Light energies above 1400 nm would cause
surface and skin burns and do not affect the retinal area.
Classification of Lasers
Manufacturers of lasers and laser products in the U.S. are regulated by the Food
and Drug Administration's Center for Devices and Radiological Health (FDA/
CDRH) under 21 CFR 1040. These regulations require manufacturers to certify
each laser or laser product as belonging to one of four major Classes — Class I,
II, IIa, IIIa, IIIb, or IV. Lasers are classified according to the accessibly emission
limits and their potential for causing injury. Lightwave systems are generally
classified as Class I, because, under normal operation conditions, all energized
laser transmitting circuit packs are terminated on optical fibers which enclose the
laser energy with fiber sheath, forming a protective housing. Also, covers are in
place over the circuit pack shelves.
Содержание DDM-2000 OC-12
Страница 1: ...363 206 295 Issue 1 December 1997 DDM 2000 OC 12 Multiplexer Release 7 0 User Service Manual Volume I ...
Страница 37: ...Tables xxxviii Issue 1 December 1997 A A SONET Overview A 1 SONET Payloads A 18 A 2 SONET Transport Rates A 19 ...
Страница 506: ...INS PROG 8 of 8 Page INS PROG COMMANDS RELATED rtrv eqpt rtrv ne OC 12 DDM 2000 1997 December 1 Issue 11 89 ...
Страница 528: ...RTRV ATTR ALM 2 of 2 Page RTRV ATTR ALM COMMANDS RELATED set attr alm OC 12 DDM 2000 1997 December 1 Issue 11 111 ...
Страница 565: ...RTRV OC3 3 of 3 Page RTRV OC3 COMMANDS RELATED rtrv sync 11 148 1997 December 1 Issue OC 12 DDM 2000 ...
Страница 664: ...SET FEAT 3 of 3 Page SET FEAT COMMANDS RELATED rtrv feat OC 12 DDM 2000 1997 December 1 Issue 11 247 ...
Страница 766: ... Ctl T TOGGLE 2 of 2 Page Ctl T TOGGLE COMMANDS RELATED logout rlgn OC 12 DDM 2000 1997 December 1 Issue 11 349 ...
Страница 847: ...Multiplexer OC 12 DDM 2000 7 Release TARP TOP Manual User Service II Volume 363 206 295 1 Issue 1997 December ...
Страница 867: ...363 206 295 TOP Maintenance and Operation BLANK LEFT INTENTIONALLY PAGE THIS 12 1997 December 1 Issue ...
Страница 1145: ...Order Circuit 363 206 295 NTP 029 1 of 1 Page 1997 December 1 Issue Unused LISTED ORDER IN BELOW ITEMS DO TO GO DETAILS FOR ...
Страница 1146: ...Order Circuit 363 206 295 NTP 030 1 of 1 Page 1997 December 1 Issue Unused LISTED ORDER IN BELOW ITEMS DO TO GO DETAILS FOR ...
Страница 1182: ...Turnup System 363 206 295 NTP 033 1 of 1 Page 1997 December 1 Issue Unused LISTED ORDER IN BELOW ITEMS DO TO GO DETAILS FOR ...
Страница 1243: ...Clearing Trouble 363 206 295 TAP 107 1 of 1 Page 1997 December 1 Issue Unused ...
Страница 1393: ...363 206 295 DLP 513 1 of 1 Page 1997 December 1 Issue Unused ...
Страница 1394: ...363 206 295 DLP 514 1 of 1 Page 1997 December 1 Issue Unused ...
Страница 1456: ...363 206 295 DLP 523 7 of 7 Page 1997 December 1 Issue OC 12 via Access Broadcast Video for Cross connections of Example 4 Figure ...
Страница 1465: ...DLP 525 363 206 295 1997 December 1 Issue 6 of 2 Page Schematic Ring Virtual ATM Sample 1 Figure ...
Страница 1469: ...DLP 525 363 206 295 1997 December 1 Issue 6 of 6 Page Ring Virtual ATM OC 12 DDM 2000 for Cross connections of Example 4 Figure ...
Страница 1565: ...363 206 295 DLP 543 6 of 5 Page 1997 December 1 Issue Network Broadcast Video of Test Transmission 2 Figure ...
Страница 1566: ...DLP 543 363 206 295 1997 December 1 Issue 6 of 6 Page Network Ring Virtual ATM of Test Transmission 3 Figure ...