How To Determine The Right Fiber Optic Network Backup Switch For Your Application

How To Determine The Right Fiber Optic Network Backup Switch For Your Application

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1. Questions to Consider in the Design of Your Switch.
A. How many positions does your application require?
i. Two-position and three-position switches are very common. Complex multi-position switches are also required.

B. What type of connector or port preference? The selection of connectors include ST, SC, LC, ESCON and others.
i. ST connectors use a plug and socket that is locked in place with a half-twist bayonet lock.
ii. SC connectors feature a push-pull latching system providing speedy insertion and
removal along with a positive connection.
iii. LC connectors are smaller versions of the SC connectors.
iv. ESCON connectors have two 2.55 mm ceramic ferrules and a robust strain relief design.

C. Fiber Requirement: Simplex or Duplex?
i. In configuring your backup switch, a determination on the fiber type, simplex or duplex needs to be made.
1. Simplex fiber optic cable consists of a single fiber, and is primarily used in applications that only require one-way data transmission. Simplex fiber is available in both singlemode and multimode. Simplex means the cable has only one thread of fiber optic glass inside the single core and one single outer jacket.
2. Duplex cable consists of two fibers, usually in a zipcord (side-by-side) style. Duplex multimode or single mode fiber optic cables are used for applications that require simultaneous, bidirectional data transfer. Workstations, fiber switches and servers, fiber modems, and similar hardware usually require duplex cable. Duplex fiber is available in singlemode and multimode. Duplex fiber cable can be regarded as two simplex cables having their jackets joined by a jacket material. Some duplex fiber optic cables have clips on the two fiber optic connectors at each side of the cable to combine the two connectors together.

D. Mode: Multimode or Singlemode?
i. Multimode fiber optic cable has a large diameter core that is much larger than the wavelength of light transmitted, and therefore has multiple pathways of light. Several wavelengths of light may be used in the fiber core. Multimode optical cable is most commonly used for shorter distances, such as a building or a campus. Typical multimode links have data rates of 10 Mbit/s to 10 Gbit/s over link lengths of up to 600 meters.
ii. Singlemode fiber optic cable has a small core and only one pathway of light. With only a single wavelength of light passing through its core, singlemode realigns the light toward the center of the core instead of simply bouncing it off the edge of the core as with multimode. The glass fiber diameter is usually 8.3 to 10 microns. Single mode fiber provides a higher transmission rate and up to 50 times more distance than multimode.

E. Switch Specifications: Wavelength, Speed, Fiber Size, Simplex, Duplex, Interface Conversion will be unique to your network. Examples of two switches with very different specs follow.

F. Technology Preference: All Optic, Optic/Electronic/Optic, No Preference?
i. All-Optic (O-O-O) Fiber optic network switches designed with scalable all-optical, O-O-O, MEMS (Micro-Electromechanical System) technology employ control mechanisms to tilt mirrors or direct prisms in multiple directions to manage light signals without converting the signals to electrical and back to optical. This increased level of control minimizes insertion loss and keeps the features of high data rate and protocol transparency.
ii. Optic/Electronic/Optic (O-E-O) Technology Optic/Electronic/Optic technology is both economical and reliable, however such an architecture prevents the switch from performing with the same speed as an all-optical scheme and is not transparent to network protocols used.

G. Chassis Type: Rackmount or Desktop? This table lists a variety of switches built to fit equipment racks and desktops.

H. Security Concerns can be addressed in a variety of ways.
i. Off-line positions.
1. External Off-line Position The block diagram of the Model 4192 Fiber Optic SC Duplex A/B/C/D/Off-Line Switch illustrates a fiber optic switch with an external off-line position. This switch enables a fiber optic device connected to the SC Duplex COMMON connector of the unit to access any of the four fiber optic networks connected to the A, B, C, or D ports, or to disconnect completely from all output ports. The switch position can be changed via a pushbutton or via a device connected to the Remote port. Applying the appropriate voltage to the designated pins of the Remote connector will cause the switch to change position.

2. External Off-Line Position with Switch Position Memory The Model 4196 4-Way All-Optic Fiber Switch, Multimode, 62.5/125 Microns with a Fully Decoupled Off-Line Capability allows a fiber optic device connected to the units SC Duplex COMMON connector to access any of the four fiber optic networks connected to the A, B, C, or D ports, or to disconnect completely from all output ports. Switch position can be changed via front-panel pushbuttons or by a device connected to the rear panel Remote port. Applying appropriate voltage to designated pins of the Remote connector also changes the switch position. The Off-Line pushbutton uncouples all fiber ports from each other. The Model 4196 has Switch Position Memory. When power is lost, the Model 4196 automatically changes to the Off-Line position and decouples all fiber connection in and out of the unit. When power returns, the Model 4196 automatically reads the voltages on the Remote port and looks to the pushbutton activity to select its switch position.

3. Internal Off-Line Position with Options The Model 6275 ST Duplex Fiber Optic 8-Position Switch with Off-Line Position and Remote Serial Control provides both an Off-Line position and a keylock to lock out the front panel pushbutton controls. The Model 6275 features both local and remote control. The Off-Line position is a valid state to preserve network and data isolation. The user can configure the switch to either maintain its position and data pathways on power failure or to revert to the Off-Line position during power failure. A key is provided to lockout the front-panel pushbutton controls.

ii. Front Panel Lockout - The Model 6293 Fiber Optic Mirror A/B/C Switch, Single Mode LC Duplex with Remote Serial Access allows sharing a fiber optic LC duplex pair connected to the COMMON port among three other sets of LC duplex pairs connected to the A, B, and C ports with local and remote access functionality. The front-panel pushbutton can be locked out using remote ASCII commands.

iii. PassWord Protection - Password protection is another method of providing network security. The Model 4185 Fiber Optic SC Duplex, Multimode Switch/Converter allows accessing two separate fiber optic 100 Base FX ports (ports A and B) from a 100 Base TX Fast Ethernet port (COMMON port). The fiber optic/twisted pair copper conversion is built in. This unit includes an RS232 serial security enhanced Supervisory Remote Port. Upon proper authentication, a terminal or computer in terminal mode connected to this port can communicate with the unit, determine its status, change the switch position as desired, and/or lock out the front panel switching capability. A modem can also be connected to this port to remotely access the switch. Access to the Supervisory Remote Port feature is password protected.

I. Power Loss How should your switch function during a power loss?
i. Should the switch continue to pass data?
ii. If passing data during a power loss, should data pass through the last selected switch position or go to the default position?
iii. Upon power up, should the switch remain in the last position or start up in default mode?

J.Number of Channels per Chassis - Electro Standards manufactures fiber optic backup switches ranging from Single-Channel to 16-Channel Switches.
K. Multiple channel switch control: Simultaneous or Individual.
Examples of how these switches function follow:
i. Simultaneous Channel Switching:
ii. Individual Channel Switching: All channels are switched individually with the

2. Putting the Switch All Together

3. Summary - Fiber optic switches of various functions are available to add versatility, improve efficiency, and enhance scalability of data networks. They may be operated locally by pushbutton or remotely via a variety of common communication interfaces. The agility that they add to network operational performance is limited only by the innovation of the user and the design expertise of the switch product provider.
Applications include switching to backup data lines, to test equipment, to monitoring equipment, or simply switching to off-line for security. Electro Standards Laboratories is available to provide an optimum switch solution for your application.

About the Author:
Authors Background
Raymond B. Sepe, Sr., is the President of Electro Standards Laboratories, Cranston, Rhode Island. Mr. Sepe holds electrical engineering degrees from the University of Rhode Island. As the President of Electro Standards Laboratories, he has been involved with the design and manufacture of innovative network products for over 30 years, developing state-of-the-art fiber optic network backup switches, interface converters and cable a



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