Basics of Optical Transmitters and Receivers with Specifications

At present, the growth in information technology has increased using the current telecommunication systems. Mostly, OFC (optical fiber communication) plays an essential role in the telecommunication system development with a high speed as well as quality. Nowadays, the applications of optical fibers mainly involve in telecommunication systems and also in the Internet & LAN (local area networks) to attain high signaling rates. The optical fiber communication module mainly includes transmitter module like PS-FO-DT as well as receiver module like PS-FO-DR. The communication of fiber-optic digital data transmission & reception can be done using plastic fiber cable. This article discusses an overview of optical transmitters and receivers, its specifications.

What are Optical Transmitters and Receivers?

The optical fiber communication system mainly includes a transmitter and receiver where the transmitter is located on one ending of a fiber cable & a receiver is located on the other side of the cable. Most of the systems utilize a transceiver which means a module which includes transmitter and receiver. The input of the transmitter is an electrical signal and it converts into an optical signal from LED or laser diode.

The light signal from the transmitter end is connected to the fiber cable using a connector & is broadcasted through the cable. The light signal from the fiber end can be connected to a receiver wherever a detector changes from the light to an electrical signal then it will be conditioned appropriately to use by the receiving equipment.

Transmitter

In the FOC system, the light source like an LED or laser diode is used as a transmitter. The main function of a light source like LED / Laser is to change an electrical signal into the light signal. These light sources are small semiconductor devices which efficiently converts electrical signal to light signal. These light sources require connections of power supply and modulation circuitry. All these are generally connected within one IC package. The best example of the transmitter LED is HFBR 1251. This kind of LEDs requires an external driver circuit. Here we IC 75451can be used for driving the light source.

Transmitter Specifications

• Type of LED is DC coupled
• Interface connectors are 2mm socket
• The wavelength of source is 660nm
• Supply current is a maximum of 100 mA
• A serial port is Max232 IC Driver
• Type of input signal is digital data
• The LED driver is on board IC Driver
• The interface of LED is self-locking Cap
• Highest input voltage is +5V
• Data rate speed is 1 Mbps
• Supply Voltage is +15V DC

Sources of Fiber Optic Transmitter

The fiber optic transmitter uses sources based on several criteria’s like diodes, DFB laser, FP lasers, VCSEL, etc. The main function of these sources is to changes from an electrical signal to an optical signal. All these are semiconductor devices.

The LEDs & VCSELs are made-up on semiconductor wafers to produce light from the outside of the chip, whereas f-p laser emits from the surface of the chip as of a laser cavity formed within the center of the chip.

The outputs of LEDs have low-power outputs compare with lasers. The bandwidth of LEDs is less compare with lasers Due to the fabrication methods of LEDs & VCSELs, they are inexpensive to build. But lasers are expensive due to the laser cavity within the device.

Specifications of Different Fiber Optic Sources

The different fiber optic sources are LED, Fabry-Perot Laser, DFB Laser, and VCSEL

For LED

• Wavelength in nm is 850, 1300
• Power into Fiber in dBm is -30 to -10
• Bandwidth is <250 MHz
• Type of Fiber is MM

For Fabry-Perot Laser

• Wavelength in nm is 850, 1310 (1280-1330), 1550 (1480-1650)
• Power into Fiber in dBm is 0 to +10
• Bandwidth is >10 GHz
• Types of Fibers are MM, SM

For DFB Laser

• Wavelength in nm is 1550 (1480-1650)
• Power into Fiber in dBm is 0 to +25
• Bandwidth is >10 GHz
• Type of Fiber is SM

For VCSEL

• Wavelength in nm is 850
• Power into Fiber in dBm is -10 to 0
• Bandwidth is >10 GHz
• Type of Fiber is MM

Optical Fiber

An optical fiber is the transmission medium within FOC systems. Here, optical fiber is the crystal clear and stretchy filament which transmits the light from a transmitter end to a receiver end. When the optical signal enters at the transmitter end of fiber then optical communication system transmits to the end of the receiver using the optical fiber.

Receiver

In the FOC system, a photodetector can be used as a receiver. The main function of the receiver is to change an optical data signal back to an electrical signal. This is a semiconductor photodiode in photodetector in current FOC system. This is a small device generally fabricated jointly with electrical circuitry to form an IC package to offer connections like power supply & signal amplification. The best example of the receiver photodetector is HFBR 2521. This kind of photodiode includes driver circuit so it doesn’t require an external driver circuit.

Receiver Specifications

• Type of photodiode is DC coupled
• The interface connector is 2mm socket
•  The wavelength of diode ranges from 660nm to 850nm
• The maximum current supply is 50mA
• The speed of data rate is 5 Mbps
• Index of fiber cladding is 1.402
• The interface of the photodiode is the self-locking cap
• The optical cable is plastic fiber multimode
• Receiver driver is internal diode driver
• The serial port is Max232 IC Driver

Thus, this is all about optical transmitters and receivers. The fiber optic source used in the transmitter is LED otherwise laser source & electronics for signal conditioning is mainly used for adding a signal into fiber. The receiver in fiber optic captures the light signal from a FOC, and decodes the binary information and transmits it into an electrical signal.

The data can be transmitted from an LED source to a transmitter through an electrical signal. After that, it takes the binary information & transmits it in the direction of a light signal. The light signal can be transmitted by means of FOC until it arrives at the receiver. Then the receiver receives a light signal to decode it back to an electrical signal to allow the binary information to be studied by the operator. A transceiver of FOC is one kind of device which unites both the transmitter & receiver functions.