The OFT project is based on a fibre optic transmitter an receiver (FB104). The transmitter is based on a high-output medium-speed infrared LED while the transceiver is built on a high-sensitivity NPN phototransistor. Both are housed in a connector-less style plastic fiber optic package. The transmitter has a typical peak wavelength of 930nm. The bandwith of the receiver is between 400nm to 1100nm. The maximum photosensitivity is around 870nm. The receiver and transmitter is connected with an RX and TX LED over a NE555 timer circuit to indicate if a data transmission occurrs.

Note that the IF-D92 is suitable for digital data links at rates up to 20kbps!

Experience	Level
Soldering
Mechanical

There are two parts of the hardware. The pcb and the housing of the OFT. The pcb is created with KiCAD and the housing with FreeCAD. All files are built with github actions so that they are ready for a production environment. The housing is printed with a 3D-printer (Dremel 3D40).

The circuit board is populated on both sides (Top, Bottom). The best way for soldering the SMD components is within a vapor phase soldering system and for the THT components with a standard soldering system.

The housing has a tolerance of 0.2mm on each side of the case. So the pcb should fit perfectly in the housing. The tolerance can be modified with FreeCAD in the Parameter Spreadsheet.

The OFT is powerd with 5V. The RX pin serves as an output and stores the received data at the output so that it can be read by the device. The TX pin servs as an input and sends the received data at the input over the fibre channel. The levels of both pins are LOW = 0V and HIGH = 5V.

#
#                                      +----------------+      +---------------------+
#                                      |    U       +---+---+  |                     |
#                                      |    S       |  USB  |--+ +-----------------+ |
#                                      |    B       +---+---+  | | TeraTerm        | |
#              +-------------+         |    /           |      | | ~~~~~~~~        | |
#              |      O      |         |    U           |      | | ~~~~~           | |
#            +--+--+  F   +--+--+   +--+--+ A           |      | | ~~~~~~~~~~~~    | |
#      L +---+ ORX |  T   | VCC +---+ VCC | R           |      | |                 | |
#      O |   +--+--+      | GND +---+ GND | T  +-+      |      | +-----------------+ |
#      O |      |         +-----+   +-----+   / /       |      |                     |
#      P |   +--+--+      | RXD +---+ RXD | +-+-+-+-----+      | Computer            |
#      B +---+ ORX |      | TXD +---+ TXD | | 5V  | 3V3 |      |                     |
#      A     +--+--+      +--+--+   +--+--+ +-----+-----+      +---------------------+
#      C       |             |
#      K       +-------------+                                            
#

The maximum baudrate should be about ~19200bps!

R. GAECHTER