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Fiber Circuit: A Beginner’s Guide to the Communication System

Fiber Optic Setup

Source: Wikimedia Commons

In the past, electrical cabling was the main thing till people needed high bandwidth over a long distance. Unfortunately, the electrical cables couldn’t meet the criteria. Hence, it needed a more efficient replacement. And the fiber optic came along. Interestingly, you can rely on fiber optics to conduct large amounts of data at extremely high speeds. So, it’s no surprise that you find it in most internet cables. But the technology has some drawbacks like fiber circuit failure, which is negligible—especially for high-density multi-fiber arrays.

Want to know more? You’re in the right place because we’ll discuss more on the compact, chronically implantable, high-density arrays of fiber optic circuits.

Let’s proceed! 

What is a Fiber Circuit?

Fiber optics uses the same idea of the movement of information in different ways. For instance, the telephone has a wire cable.

Fiber Optic Circuit

Fiber Optic Circuit

Source: Wikimedia Commons

Hence, the fiber circuit is a path where electrons travel with information. And these electrons move to different electrical devices. Also, it comes with a light that acts as the information carrier. And this light spreads with the help of the total internal reflection via a transparent optical waveguide.

Hence, the cable takes the sound into the socket in the wall as you speak into the device. Plus, it has no behavioral deficits. Consequently, another line will move the sound to the local telephone exchange and probably face an initial overload failure.

But, the cellphone, on the other hand, works differently. The device works by transmitting and receiving information with invincible radio waves and large-scale neural dynamics. So, this happens because cell phones don’t use cables. 

Types of Optical Fibers

Now, you know a bit about fiber optics; it’s crucial to understand that they transmit signals in different modes with additional safeguards. The method refers to the way that a light beam passes down the fiber.

So, the signals may bounce down the fiber at different angles, go straight down to the fiber’s middle, or bounce the thread down at a low angle.

That said, we have two major types of fiber optic cables: 

Single-mode Fiber

This fiber has a small diameter of the glass fiber core. So, it’s ideal for long distances. Also, it reduces your chances of having a reduction in signal strength. And it’s all thanks to the small diameter.

Further, the single-mode fiber’s small opening helps to separate light into a single beam. Consequently, the cable provides a more direct route. The single-mode fiber uses a laser light source, and it has a high bandwidth.

Also, this fiber needs the exact calculation to generate the laser light in its small opening. Hence, it’s more expensive.

Multimode Fiber

The multimode fiber is the opposite of the single-mode fiber. So, it has a large core opening that permits light signals to bounce and reflect as it goes down the fiber.

And thanks to its large diameter, the fiber can send multiple light pulses down the cable at once. Hence, you’ll have more data transmission.

Also, it means that you may experience signal loss and interference. Plus, the multimode fiber uses an LED to generate a light impulse, and it’s cheaper than the single-mode fiber.

How Does the Fiber Circuit Work?

The fiber circuit works by moving information in photons or light particles that vibrate through a fiber optic cable.

That said, it’s vital to note that the cladding and glass core fiber has a different refractive index. Hence, the core and cladding bend the incoming light at a particular angle.

So, when the light signals move down the fiber optic, they experience total internal reflection. Comprehensive internal review happens when light signals reflect off the core (the central part of the cable) and cladding (a layer of glass that wraps around the outer part of the core).

And this usually happens in a sequence of zig-zag bounces. Also, the total internal reflection is one of the things that ensure that light remains in the pipe.

But the signals tend to travel 30% slower than the speed of light due to the denser glass layers. Also, if you want to boost the signal throughout its journey, use repeaters at distant intervals.

Why do you need repeaters? They help to regenerate optical signals. And they do this by changing visual to an electrical signal. Then, the repeater processes it and retransmits the electrical signal to optical. 

Fiber Circuit: Applications

Fiber optics works by transmitting data coded in a beam of the light modulator, and it also comes in handy for network modulation. Then, the information moves down a pipe (plastic or glass). The idea behind this design came up in the 1950s. 

And the idea was for coupling efficiencies, endoscopes, and efficient grating couplers. Also, it helped doctors view the human body internally, using multi-fiber photometry, without cutting it open.

So, engineers liked the idea and used the same technology for moving telephone calls at the speed of light. Soon, the Federal Communications Commission (FCC) embraced the technology. That said, the fiber optic cable consists of optical fibers (thin strands of plastic or glass).

Also, each of the fibers is relatively thin and can carry over 25,000 telephone calls. Hence, the entire cable can transmit several million calls with ease. In summary, fiber optic cables use light-based technology to move information between two places. 

The Fiber Optic Circuit Design

Fiber Optic Circuit Design

Fiber Optic Circuit Design

Source: Researchgate c/p Richard Cole

The circuit design has two significant parts we’ll discuss separately: the transmitter and receiver circuit. 

Fiber Optic Transmitter Circuit

Here are the components you need to build a low-cost fiber optic transmitter circuit:


  • Case
  • SK1 3.5mm jack board
  • Circuit board


  • D1 (LED)
  • IC1 (NE555)
  • IC2 (1458C)
  • Tr1 (BC141)


  • C1 (220m 10V elect)
  • C2 (390pF ceramic plate)
  • C3 (1u 63V elect)
  • C4 (330p ceramic plate)
  • C5 (4n7 polyester layer)
  • C6 (3n3 polyester layer)
  • C7 (470n polyester layer)

Resistors (all 1/4 watt, 5%)

  • R1 (47R)
  • R2 (4k7)
  • R3 (47k)
  • R4 (10k)
  • R5 (10k)
  • R6 (10k)
  • R7 (100k)
  • R8 (100k)

Since your IC1 is NE555, you should expect a decent performance efficiency. Also, you can control the frequency by joining the input signal to the IC‘s pin 5.

And the pin connects with the voltage divider. That said, you need to configure your voltage divider to generate the 2/3V+ and 1/3V+ switching limits for the NE555.

Further, it’s vital to increase or decrease the upper limit. That way, you can increase or decrease the time that C2 takes to switch between the two ranges. Since the TR1 offers the high drive current that illuminates D1 (LED) ideally, you have to wire it like an emitter follower buffer stage.

Also, apart from the IC1 with a decent 200mA current for the D1, you need a separately controlled driver for your LED. And this will help you get your preferred LED current precisely and reliably.

In addition, position the R1 to fix the LED current, which is about 40mA. While you’re at it, note that the LED can only work with 50% (20mA) of the actual rating. And this happens because the LED switches ON/OFF at a rate of 50%.

Plus, you can adjust the R1 value when necessary—to increase or decrease the output current.

Fiber Optic Receiver Circuit

The components you need for the receiver circuit and filter are:


  • TR1, TR2 BC549 (2 off)
  • D1
  • IC1 (4001BE)
  • IC2 (1458C)
  • IC3 (CA3140E)


  • C1 (100m 10V electrolytic)
  • C2 (2n2 polyester)
  • C3 (2n2 polyester)
  • C4 (390p ceramic)
  • C5 (1m 63V electrolytic)
  • C6 (3n3 polyester)
  • C7 (4n7 polyester)
  • C8 (330pF ceramic)
  • C9 (3n3 polyester)
  • C10 (4n7 polyester)


  • R1 (22k)
  • R2 (2M2)
  • R3 (10k)
  • R4 (470R)
  • R5 (1M2)
  • R6 (4k7)
  • R7 (22k)
  • R8 (47k)
  • R9 (47k)
  • R10 – R15 10k (6 off)

The fiber optic receiver is above the filter. And it’s the receiver’s output that connects with the filter circuit’s input.

The D1 creates the detector diode. And it functions in the reverse bias setting. Consequently, the leakage resistance forms an LDR effect.

R1, on the other hand, behaves like a load resistor. Plus, the C2 forms the link between two points: detector stage and input amplifier. As a result, there will be a two-stage capacitively connected network. And the two locations will work simultaneously in the common-emitter mode.

It’s possible to push the monostable multivibrator—If you provide an efficient high input voltage oscillation at the semiconductor (TR2).

And it will permit a superior overall voltage gain (>80dB). The filter stage builds around 1458C (a/b). Plus, it’s an 18 dB per octave (2/3rd order) filter system with details commonly used in transmitter circuits.

Pros of the Fiber Optic

  • You can submerge fiber optics in water
  • It can support high bandwidth capacities
  • The cables are light, thin, and strong
  • It doesn’t need a signal boost to allow light to travel further
  • The fiber optic doesn’t need frequent maintenance or replacement
  • Less prone to electromagnetic interference

Cons of the Fiber Optic

  • It’s quite pricey
  • Installation is labor-intensive
  • The cables are fragile
  • The glass fibers need more protection

Final Words

The fiber circuit plays a vital role in fiber optics as a whole. And most people prefer fiber optics cables over copper cables. And it’s no surprise considering that the former has benefits like high transmission speed, bandwidth, etc. Plus, they work perfectly for high-performance data networking and long-distance.

What do you think about the fiber circuit? Do you have questions or suggestions about the topic? Please feel free to reach us.

Hommer Zhao
Hi, I am Hommer, the founder of WellPCB. So far, we have more than 4,000 customers worldwide. If you have any questions, you can feel free to contact me. I really appreciate any help you can provide.