Optics and Wave Jan. 23, 2018

• LAN: 10Base2, 10BaseT, 100BaseT, Gigabit Ethernet (1Gb/s, 10Gb/s). Currently, 10 Gb/s channels in a fiber and very soon 40 Gb/s channels in a fiber.

• WAN: T1 line (1.544 Mb/s)
High speed undersea optical fiber cables (thousands of km long, transmitting in 40Gb/s)
Notes: Merit is in speed times distance product.

• Established optical network: Based on time division multiplex (TDM) called Synchronous Optical Network (SONET). Their speeds are limited by electronics switching time to 40Gb/s.

• Three options for upgrade:
1. Increase speed per channel.
2. Increase number of fibers.
3. Increase number of channels in a fiber.
Based on promising wavelength division multiplexing (WDM). Provide upgrade for existing "dark fibers" by adding carriers with different wavelengths.
Avoid limitation of electronics switching.

• Feasibility of WDM: low loss and low dispersion in glass fiber for 1.3-1.6[equation], almost ideal optical amp. that can integrated with fibers, integrated optical filters, integrated solid state lasers and photodetectors, possibility of constructing all-optical components, such as multiplexer, demultiplexer, add-drop multiplexer (ADM) and optical cross-multiplexer (OXC).

These components enable the development of transparent (all-optical) networks that eliminate electrical-optical (E-O) and optical-electrical (O-E) conversions in opaque links for popular WDM bands: S-band (short) -- 1460 to 1530 nm, C-band (conventional) -- 1530 to 1565 nm and L-band (long) -- 1565 to 1625 nm.
The last two components (ADM & OXC) is required for the implementation of packet switched network where the bandwidth of each channel can be adjusted dynamically, e.g. Ethernet. This is in contrast to the fixed channel bandwidth of a circuit switched network.

New network applications : metropolitan area networks (MAN), fiber to the home (FTTH), Storage area network (SAN).

A chapter on communication systems from Rizzoni's book.

• Maxwell equations: (Read Sec. 7.2-7.6 of EE361 Text book)
[equation] by [equation]
[equation] by [equation]
Wave equation (Appendix D of text) [equation] where [equation], permittivity [equation], and permeability [equation].
Refractive index [equation] and [equation] if [equation] where [equation] is speed of light in air.

• Equations in phasor form (time harmonic):
[equation], [equation],
Wave equation [equation]; [equation] is wave number.
Recall that [equation] ([equation] is freq, [equation] is wavelength in the medium, wavelength in air [equation])


Last Modified: January 22, 2018
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