OPTICAL SWITCHING Presented by, VIVEK.S.M S7 EC ROLL NO:

An optical communication network

The switching dilemma

Optical switching… so easy? MEMS Liquid crystals Bubbles Thermo optics

It’s not that easy as it looks.. Data traffic doubles every year. Information demand in internet creates enormous need for capacity expansion. Simple switching techniques cannot support DWDM. Optical networks are regarded as the ultimate solution to bandwidth needs of future communication.

OEO approach All traffic goes through O/E/O conversions. However, as transmission speed goes higher, this approach is neither scalable nor cost-effective (heat, power)

WAVE LENGTH DIVISION MULTIPLEXING (WDM) A technology used to increase the information rate Here multiple signals can traverse through a single strand of optic fiber

Dense Wavelength Division Multiplex (DWDM) DWDM is a variation of Wavelength Division Multiplex (WDM) but with much higher bandwidth and density. Multiple signals are carried together as separate wavelengths (color) of light in a multiplexed signal.

ADVANTAGES OF DWDM DWDM, up to 80 separate wavelengths or channels of data can be multiplexed into a lightstream transmitted on a single optical fiber. Each channel can carry up to 2.5 Gbps, therefore up to 200 billion bits per second can be delivered by the optical fiber.

OPTICAL TRANSMISSION MEDIA Links between the nodes are optical fibers. Here packets are in the optical format. O-E-O conversion are required at the interface.

LIMITATIONS LIMITED PACKET PROCESSING SLOW OPERATION COST AND COMPLEXITY CROSS TALK These limitations degrades the performance of the system affecting the bandwidth

SOLUTION! The solution is OPTICAL PACKET SWITCHING The signals are being processed by means of OPTICAL SWITCH FABRIC OPTICAL SWITCH FABRIC OPTICAL SIGNALS

GENERAL PACKET FORMAT A generic packet format consists of  Header  Payload  Additional GUARD BANDS before and after payload

PACKET HEADER A packet header may comprise of following fields  Sync- provides synchronization  Source Label-provides source node address  Destination Label-provides destination node address  Type-type and priority of the carried payload

 Sequence Number: Packet sequence number to reorder packets arriving out of order and guarantee in-order packet delivery.  OAM: Operation, Administration, Maintenance  HEC: Head Error Correction

SWITCH ARCHITECTURE An OPS node consists of following components 1.INPUT INTERFACE 2.SWITCHING MATRIX 3.BUFFER 4.OUTPUT INTERFACE 5. ELECTRONIC CONTROL UNIT

1. INPUT INTERFACE Wave length conversion ->conversion of external to internal wavelengths ->identification of the beginning and end of the header and payload Provides synchronization Header processing

2. CONTROL UNIT Processing routing information. Updates header information. Forwards header to output interface.

3. SWITCHING MATRIX Optical switching of the payloads according to the commands from the control unit.

4. OUTPUT INTERFACE Provides 3R(reamplification,reshaping,retiming) regeneration Attaches updated header to corresponding optical payload Conversion of internal to external wavelength Resynchronization

CLASSIFICATION

MEMS(Micro-electro Mechanical Systems) Software in the switch’s processor deicide where an incoming stream of photons should go. Sends a signal to an electrode on the chip’s surface that generates an electric field that tilts the mirrors. The wavelengths  Bounce off the input mirrors  Gets reflected off another mirror onto output mirror.  Output mirror direct the wavelength into another fiber.

THERMO-OPTIC SWITCH Waveguides have a core and cladding made of glass with differing indices of refraction. An input light wave is split onto two separate waveguides. No heat is applied to the lower branch, the coupler will output the waveform on to the waveguide labeled output#1. Heating element activated the output light wave ends upon the waveguide labeled output#2.

WORKING

BUBBLE SWITCH The switch consist of a silica waveguide with arrays of intersecting light pipes that form a mesh. A small hole sits at a point where these light pipes intersect. It contains an index-matching fluid (one whose index of refraction is the same as the silica).

If no bubble is present at the junction, the light proceeds down the default waveguide path. If a bubble of fluid is present at the junction, the light is shifted onto the second output waveguide.

LIQUID CRYSTAL SWITCH Principle : -when an electric field is applied to liquid crystal, the molecules line up and become opaque The molecules are so thin and straight, will allow light of a particular orientation to pass through the liquid crystal It consists of 2 components 1. CELL 2. DISPLACER

CELL AND DISPLACER CELL: Formed by placing the liquid crystal between 2 plates of glass Glass is coated with oxide materials that conducts electricity The function is to REORIENT the polarized light entering the cell DISPLACER: It is a composite crystal that directs the polarized light leaving the cell

CONCLUSION Optical packet switched networks has great potential and can support much higher capacities than may be possible with electronic packet switched networks. The new technology –regarded as ULTIMATE SOLUTION to bandwidth needs PROVIDING ->IMPROVED EFFICIENCY ->LOW COSTS ->UTILISE DWDM

THANK YOU

Thanks to.. Father of optical communication Father of optic fiber Pashaura SinghJun-ichi Nishizawa