FIBER OPTICS CCTV TRANSMISSION PRINCIPLES PRACTICE Types of
FIBER OPTICS CCTV TRANSMISSION PRINCIPLES & PRACTICE
Types of Transmission 1. - Analog Transmission intensity modulation (IM) frequency modulation (FM) - Digital Transmission transmission of analog video inputs transmission of digital video inputs 2.
Analog Intensity Modulation Transmission Intensity or brightness of fiber optics emitter (LED) is varied in proportion to the level of the incoming signal. Receiver then produces an output which is controlled by the Automatic Gain Control (AGC) to produce an identical output. Fiber attenuation Tx Incoming signal Launched light intensity Rx Received light intensity Outgoing signal AGC
Limitations of Intensity Modulation Light o/p - Non-linearity of LED Signal I/p - Electrical Interference (noise) Tx Incoming signal - Rx Outgoing signal Restrictions on signal format due to AGC Bright scene
Limitations of Intensity Modulation Light o/p - Non-linearity of LED Signal I/p - Electrical Interference (noise) Tx Incoming signal - Rx Outgoing signal Restrictions on signal format due to AGC Dark scene
Analog Transmission - Frequency Modulation Transmitter generates a high frequency carrier signal. Frequency of this carrier is varied according to level of incoming signal. Receiver amplifies and clips (to eliminate AM noise) then demodulates to recover the original signal. Fiber attenuation Tx Incoming signal Launched light intensity Rx Received light intensity Outgoing signal
Benefits of Frequency Modulation • System is less dependent on LED linearity. • Transmission is immune to AM interference. • AGC operation does not restrict signal format. • Multiple carrier frequencies permit two or more signals to be multiplexed on to one fiber. • Can be used for transmission of either analog or data signals, or both.
Digital Transmission of Analog Signals Transmitter codes incoming signal into a series of 1’s and 0’s for transmission over the fiber. Receiver decodes the recovered 1’s and 0’s into the original signal. Tx Incoming signal A D Fiber attenuation Launched light intensity Received light intensity Rx D A Outgoing signal
Analog to Digital Conversion Incoming Signal Sampled Signal (at 2 x highest frequency) Signal Amplitude 3456789998643113456899875421234578987532112346789 Binary Coded Signal 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1000, 0110, 0100, 0011, 0001, 0011, 0100, 0101, 0110, 1001, 1000, 0111, 0100, 0010, 0001, 0010, 0011, 0100, 0101, 0111, 1000, 1001, 1000, 0111, 0101, 0010, 0001, 0010, 0011, 0100, 0111, 1000, 1001
Benefits of Digital Transmission • System virtually independent of device linearity. • Total immunity to AM interference. • Receiver AGC is not required. • Signals can be regenerated within repeaters without loss of quality or added noise. • Multiplexed signals can be inserted or extracted with ease.
Limitations of Digital Transmission - Uncompressed video requires very large data rates e. g. 270 Mb/s per channel for Rec. CCIR 601 - Until recently effective compression techniques were either very expensive, or unacceptably slow.
Principles of CCTV Video Transmission
Image Scanning The image is scanned with a series of horizontal lines. At every point, the camera tube converts the image brightness into a proportional electrical voltage. Voltage 1. 0 V 0. 3 V Peak white Black level 0 V Time
Screen Resolution (625 lines) 625 lines 575 visible ‘TV lines’ Active Picture Area 833 pixels (4: 3 aspect ratio)
Video Bandwidth (625 Lines) 833 ‘lines’ wide (4: 3 ratio) No. of pixels per frame = 625 x 833 = 520, 625 No. of frames per second = 25 Therefore maximum pixel rate = 25 x 520, 625 = 13, 015, 625 i. e. 13 Mpixel/s Maximum analogue frequency is only the maximum pixel rate. 625 half lines high Therefore the required video bandwidth is approximately 0. 5 x 13 = 6. 5 MHz. Standard European TV provides a bandwidth of 5. 5 MHz, corresponding to a vertical visible screen resolution of about 485 ‘TV Lines’. This is the bandwidth of a monochrome (B&W) channel.
Color TV Transmission Components Camera Encoding Apparatus R G B Transmission Link Lens Dichroic Filters R G B Triple beam Display Tube Decoding Apparatus
Component Video Sync pulses Red R Green G B + + Luminance Y (0 - 5. 5 MHz) Blue R Y B Y Chroma C + + - (3 - 5. 5 MHz) U=R-Y Colour Difference (0 - 1. 5 MHz) V=B-Y 4. 43 MHz Carrier
Composite Video Sync pulses Red R Green G B + + Luminance Y (0 - 5. 5 MHz) Blue R Y B Y + Composite Video (0 - 5. 5 MHz) Chroma C + + - (3 - 5. 5 MHz) U=R-Y Colour Difference (0 - 1. 5 MHz) V=B-Y 4. 43 MHz Carrier
Composite Video Spectrum (PAL) Luminance (B & W) Signal Chrominance (Colour) Signal 0 4. 43 MHz 6 MHz
PTZ Camera Video & Telemetry Data
PTZ Camera Transmission PTZ Camera Monitor Coax T. P. PTZ Keyboard
PTZ Camera Transmission PTZ Camera Monitor Coax T. P. F. O. Transmitter F. O. Receiver Optical Fibers F. O. Receiver F. O. Transmitter T. P. PTZ Keyboard
PTZ Camera Transmission PTZ Camera Monitor Coax T. P. F. O. Transmitter Optical Fiber F. O. Receiver T. P. PTZ Keyboard
Single Fiber PTZ Transmission PTZ Camera Coax T. P. 1300 nm Transmitter 850 nm Receiver 1300 nm WDM Coupler 850 nm Single Fiber Bi-directional Transmission Monitor 1300 nm WDM Coupler 850 nm 1300 nm Receiver 850 nm Transmitter Coax T. P. PTZ Keyboard
PTZ Data Formats, b. f. (before fiber)
TTL Data Transmission Signal Line Tx Rx Earth Return Maximum distance a few metres +5 v Logic 1 Line imped Logic 1 ance 0 v Logic 0 Noise & pick-up
RS 232 Data Transmission Signal Line Tx Rx Earth Return Maximum distance 15 - 100 metres +15 v Logic 1 Line imped ance +3. 0 v 0 v -3. 0 v Noise & pick-up -15 v Logic 0
RS 232 3 -wire Fiber Connections Tx Tcvr A Data in Gnd Rx Data out Fiber Options Modem 1 or 2 fibers Fiber Options Modem Data out Rx Gnd Data in Tx Tcvr B
Balanced Line (RS 422) Data Transmission +5 V Signal Line A 0 Signal Line B +5 V Twisted Pair Tx 0 Cabling
Balanced Line Noise Rejection Signal o/p = A - B + 5 v +5 V 0 Twisted Pair Cabling +5 V 0 Noise & Interference + Differential Input Receiver - 5 v
RS 422 4 -wire Fiber Connections Tcvr A Tx. B Rx. A Rx. B Data in +ve Data in -ve Data out +ve Data out -ve Fiber Options Modem 1 or 2 fibers Fiber Options Modem Data out +ve Data out -ve Rx. A Rx. B Data in +ve Data in -ve Tx. A Tx. B Tcvr B
RS 422 PTZ Data Network PTZ Camera 1 PTZ Camera 2 PTZ Camera 3 PTZ Controller & Expander
RS 422 PTZ Fiber Network PTZ Camera 1 S 732 DVT PTZ Camera 2 fiber(s) S 732 DVT PTZ Camera 3 PTZ Controller & Expander S 732 DVR S 732 DVT
RS 422 PTZ Data Network PTZ Camera 1 PTZ Camera 2 PTZ Camera 3 PTZ Controller & Expander
RS 422 Databus Network PTZ Camera 1 Is this possible ? ? ? PTZ Camera 2 PTZ Camera 3 PTZ Controller & Expander
RS 422 Databus Network - outgoing data PTZ Camera 1 PTZ Controller Tx. A Tx. B Rx. A Rx. B + - PTZ Camera 2 PTZ Camera 3
RS 422 Databus Network - outgoing data - OK PTZ Camera 1 PTZ Controller Tx. A Tx. B Rx. A Rx. B + PTZ Camera 2 PTZ Camera 3
RS 422 Databus Network - return data PTZ Camera 1 PTZ Controller Tx. A Tx. B Rx. A Rx. B + PTZ Camera 2 - + PTZ Camera 3 - + -
RS 422 Databus Network - return data PTZ Controller Tx. A Tx. B PTZ Camera 1 PTZ Camera 2 - + Rx. A ? ? ? Rx. B ? ? ? Conflict + PTZ Camera 3 - + -
The solution - tristate RS 485 PTZ Camera 1 PTZ Controller Tx. A Tx. B Rx. A Rx. B off PTZ Camera 2 off PTZ Camera 3 off off
The solution - tristate RS 485 PTZ Camera 1 PTZ Controller Tx. A Tx. B Rx. A Rx. B - + PTZ Camera 2 off PTZ Camera 3 off off
The solution - tristate RS 485 PTZ Camera 1 PTZ Controller Tx. A Tx. B Rx. A Rx. B + PTZ Camera 2 - off PTZ Camera 3 off off
RS 422 vs RS 485 Signal Levels Logic ‘ 1’ (+5 v) RS 422 (bi-state) 0 V Logic ‘ 0’ (-5 v) Logic ‘ 1’ (+5 v) RS 485 (tri-state) ‘off state’ Logic ‘ 0’ (-5 v) RS 485 (tri-state with offset) Logic ‘ 1’ (+5 v) ‘off state’ Logic ‘ 0’ (-5 v)
2 -wire RS 485 PTZ Camera 1 off PTZ Controller A B off PTZ Camera 2 off PTZ Camera 3 off
2 -wire RS 485 PTZ Camera 1 Rx. A PTZ Controller Tx. A Tx. B Rx. B PTZ Camera 2 PTZ Camera 3 Rx. A Rx. B
2 -wire RS 485 PTZ Camera 1 Rx. A PTZ Controller Tx. A Tx. B Rx. B PTZ Camera 2 PTZ Camera 3 Rx. A Rx. B
2 -wire RS 485 PTZ Camera 1 off PTZ Controller A B off PTZ Camera 2 off PTZ Camera 3 off
2 -wire RS 485 PTZ Camera 1 Tx. A PTZ Controller Rx. A Rx. B Tx. B PTZ Camera 2 off PTZ Camera 3 off
2 -wire RS 485 PTZ Camera 1 Tx. A PTZ Controller Rx. A Rx. B Tx. B PTZ Camera 2 off PTZ Camera 3 off
2 -wire RS 485 PTZ Camera 1 off PTZ Controller A B off PTZ Camera 2 off PTZ Camera 3 off
2 -wire RS 485 Transmission Controller Camera 1 Controller Camera 2 Camera 3 Camera 2 Controller Camera 1 Camera 2 Camera 3
2 -wire RS 485 Databus Network PTZ Camera 1 PTZ Camera 2 PTZ Camera 3 120 ohm termination PTZ Controller A-wire B-wire
2 -wire RS 485 Databus Network PTZ Camera 1 PTZ Camera 2 PTZ Camera 3 120 ohm termination PTZ Controller A-wire B-wire Fiber Options Modem Fiber(s) Fiber Options Modem
2 -wire RS 485 Databus Network PTZ Camera 1 S 732 DVT PTZ Camera 2 Fiber(s) S 732 DVT S 732 DVR 120 ohm termination PTZ Controller S 732 DVR A-wire B-wire S 732 DVT PTZ Camera 3 Fiber(s) S 732 DVT
AUDIO TRANSMISSION SYSTEMS
Audio Transmission Signal Levels Most Fiber Options audio products are specified for an input signal level of 0 d. Bm into 600 ohms. What does this mean?
Audio Transmission Signal Levels Input Signal Voltage P = V 2 R 600 ohm Input Termination Resistor Fiber Options Audio Transmitter Od. Bm = 1 m. W of power dissipated in 600 ohms input termination
Audio Transmission Signal Levels 2. 2 V pk-pk P = V 2 R 600 ohm Input Termination Resistor Fiber Options Audio Transmitter Od. Bm = 1 m. W of power dissipated in 600 ohms input termination
Audio Transmission Signal Levels d. Bm Units +10 0 -10 -20 -30 -40 -50 pk-pk Signal 6. 9 V 2. 2 V 690 m. V 220 m. V 69 m. V 22 m. V 6. 9 m. V
OTHER AUDIO APPLICATIONS
Frequency Shift Keying (FSK) Telemetry DATA DC Coupled FSK 1 0 0 0 0 1 0 0
FSK Data Fiber Network PTZ Cam 1 PTZ Cam 2 PTZ Cam 3 Maxpro Controller
FSK Data Fiber Network PTZ Cam 1 S 732 DVT PTZ Cam 2 Fiber(s) S 732 DVT S 732 DVR Fiber(s) S 732 DVR PTZ Controller S 732 DVR PTZ Cam 3 Fiber(s) S 732 DVT
FSK Data Expander Fiber Network PTZ Cam 1 S 732 DVT PTZ Cam 2 Controller Telemetry Interface Module Fiber(s) S 732 DVT S 732 DVR Fiber(s) S 732 DVR PTZ Cam 3 Fiber(s) S 732 DVT
EVDI Paris Library, France Audio(s) B 743 AVR Video Audio(s) Video DVD Disc Player Audio(s) Video & Audio Distribution Matrix DVD Disc Player B 743 AVT Fiber Audio(s) B 743 AVR Video
TOA Hamburg Exhibition Centre, Germany Exhibition Hall 1 Exhibition Hall 2 Audio signals 360 A-T Fiber 360 A-R Audio outputs 360 A-R Fiber 360 A-T RS 485 Control Data S 711 Fiber S 711 Total of 12 Exhibition Halls TOA Audio Matrix
Access Control System PTZ Camera Telemetry Video Barrier Remote Intercom Remote Call Monitor Master Intercom
Access Control System PTZ Camera Telemetry Video Barrier Remote Intercom Remote Call Monitor Master Intercom
Access Control System PTZ Camera Telemetry Video Audio Barrier Remote Intercom Remote Call Monitor Master Intercom
Access Control System PTZ Camera Telemetry Video Audio Barrier Remote Intercom S 764 DAVT Remote Call Monitor Barrier Release S 764 DAVR Master Intercom
Other Audio Applications S 768 2 -way Audio & Video for Video Conferencing (Universities, Government Establishments & Hospitals) S 764 2 -way Audio & Data for Public Information ‘Help’ Points (Rail stations & airports) 341 A Dedicated Touchtone Phone Links (Point-to-point and remote to PABX) S 764 PTZ cameras with Engineer’s Audio Link
FIBER OPTICS CCTV TRANSMISSION PRINCIPLES & PRACTICE The End
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