Fiber 101, Part 3: Transmitters, Receivers and Fiber Optic Devices

Hi my name's Dan Detmer with Amphenol broadband solutions. Welcome to the fiber one on one training series. In this series, we're going to be covering multiple sessions, covering the basics of fiber. And this session will cover transmitters, receivers and fiber optic devices. Various training. If you have questions, feel free to put them into the chat. At the end of the training, we'll cover the questions. Fibre optic data is transmitted as pulses of light created by the transmitter with a laser or LED source and received by a photodetector. Here I'm showing a RF signal going into the transmitter. The transmitter takes electrical signal and converts to light pulses in the transmitter. This could either be an LED or a laser. It's connected to fiber optic cable, which transmits the light down the fiber to the optical receiver. The optical receiver has a detector in it that converts the light back into RF energy. A light emitting diode, which is referred to as an LCD, is a semiconductor device that emits light when stimulated by an electric circuit. Instead of generating heat at the junction, it stands for positive and negative light is generated and passes through an opening or lens. The LEDs convert electrical signal into light signals so that they may be passed on to the fiber optic cable. They're small and amid a lot of light and make them perfect for multimode applications. They're very easy to use, last longer and costs less and are also more reliable. Over on the right is the picture of the LED. You're probably very familiar with these LEDs. You see them in power equipment to indicate that it's on. Also LED lights in your house. Very similar. It's a little bit different. Designed for fiber optic applications. A laser diode, LD is a semiconductor device that emits high powered light. It's stimulated with electrical current. Over on the right is a picture of this. It looks very familiar to like a hybrid amplifier that you see on a circuit board. But as you can see, it has a little tail and that's where the light comes out. Laser diodes generate intense light at a very narrow bandwidth. They're used in transmitters for single mode fiber applications. And this is in the cable TV industry. Laser diodes are the most common type of lasers. Next, we can look at the difference between an LED versus a laser diode edge emitting LEDs. The pin and junction is formed by similar materials with different reactive indexes. The different reactive indexes are used to guide the light and create a directional output. Here in the junction, there's an opening. And this is allows the light to escape and it has a wide emission pattern. With the laser, you probably heard the term it's all smoke and mirrors. With the laser, we're using mirrors. We put a mirror and each side of the junction. On one side of the junction, the mirror. It's partially reflective and this allows the light to actually escape. And this actually puts on a very narrow emission pattern and high power. The dominant types of lasers using single mode systems are February pyro, which is RFP and a distributed feedback the RFP. And these are semiconductor lasers. The fp lasers are the regional lasers using the cable industry. It produces light at many wavelengths. It has a wide light pattern and is very low cost. And it does have moderate noise and linearity. And these are normally used in the return system to DFB lasers. They produce light at a single wavelength, and they. They're tunable. They have narrow light beams and the output can be combined with other lasers and then transmit it down the fiber. There are high cost, but they have less chromatic dispersion and they have lasers. This look at the spectral width of the different lasers. On the bottom I'm showing the wavelengths all from 12:30 to 1390, and the center is at 1310. And this is just for example, on the left is the power. The LCD is 60 nanometers wide. And the 0 power is 1 mile away. So it's a very low power, but very wide. When we look at the fp, we have a very narrow wavelength, a 4 millimeter. But the output power is 1 to 2. Milliwatts with a distributed feedback is very high power usually greater than 40 milliwatts, but it has a very narrow wavelength of 1 nanometer. Let's look at the span distances for the different optical lasers. In this chart, I have kilometers at the bottom going from 0 to 130. And then at the top, I have miles going from 0 to 80.6. First of all, look at the multimode with the LED at 850 nanometers. It has 3.5 dB of loss per kilometer. And it can go about five kilometers. We look at the LED at 1,300 nanometers. It has one dB of loss per kilometer. And this can go about 12 to 13 kilometers. With the RFP and the distributor feedback lasers at 1310 nanometers. It has 4/10 of a DB loss per kilometer. And they can go almost 90 kilometers with the DFB laser at 1,550 nanometers. It 3/10 of a DB loss per kilometer. And I can go 130 kilometers. Here I'm showing a direct modulated optical transmitter. With the direct modulators lasers, they can shift in frequency or what's called sure where first turns on which causes dispersion. Here I'm showing the directly modulated optical transmitter. When the input signal hits the laser, it actually turns the laser on and off to create output pulses of light. Every time to transmit returns on and off. It can actually cause that chirp or dispersion. To reduce that we use externally modulated transmitters. We take the laser and we produce a CW light, a continuous wave light. That light then goes into a modulator and creates the pulses of light on the output. There's also a thing called Cool lasers. High power lasers can become unstable as the operating temperature increases. This can affect the power output level and wavelength. It can actually drift fuel the application of lasers. Need to shine a light or the same distance as the high power head and hub lasers and are more prone to noise due to the heat. As atoms hit up, they move more. So technology reduces the speed of the atoms, which in turn reduces the heat generated by the atoms. Here I'm showing an example of some of the optical transmitters. On the left is a single rack mounted optical transmitter. This takes up a lot of space, too. Over on the left is a major optical transmitter. You can put multiple transmitters in one rack. Down at the bottom is a virtual hub. This is something that may be hang on the strand or in underground vaults. It comes in a housing that's easily accessible through a lid. Never look into the end of an optical connector adapter or laser output as the light can damage your eyes. This light is invisible and you can't see it with the naked eye. Next, we're going to look at urban Dog fiber amplifiers. EDF phase is an optical amplifier used to compensate for the loss through optical fibers in a long distance. Here I'm showing light pulses coming from the transmitter from it. By the time it gets down the fiber optic cable, it loses too much. And the optical receiver can't distinguish what the information was. That's where erbium doped fiber amplifiers come into play. These can be placed right at the output of the transmitters or pre amplifiers in front of the receivers. For longer distances. These can be in line. A typical distance between each phase is several Tens of kilometers. The optical receivers convert the optical light back into electrical signals through the use of photodetectors. Optical receivers usually have wide detector windows and detects all optical modes. Next, we'll look at optical splitters with the optical fiber just going in one direction. Doesn't do us much good. We need to split it off to feed different applications. Fiber splitters are very similar to the RF splitters that we have. They're going to connect devices with three or four or more devices between them. First, we're going to look at the fuse by conical taper splitters, the RFP. Ts the way we make these splitters is we take two fibers, we bring them together, wrap them around each other, put a little pressure and also heat. And we fuse these fibers together. Once it's fused together, we get rid of the fiber one in this application. So now we have one input and two outputs. The empty splitters can have up to four outputs in order to get more outputs. We do something similar to the RF splitters. We take a 4 way output splitter, optical splitter. In this case, we actually feed four more optical splitters with four outputs. And here we have six outputs. And you can get up to 32 outputs here. And that's typically what you have in fiber to the home applications. Next, we're going to look at the planar lightweight circuit, TLC splitters. And these are made very similar to semiconductors. What we do is we take the core glass and we etch it to make light paths. Then we take two cladding glasses over that and make a sandwich. Once the sandwich together, it's packaged in a small, compact package. These splitters are very compact, efficient and reliable. Next, we'll look at optical couplers. So there's times when we need more light in one direction than the other. And this would be an optical coupler, again, very similar to RF couplers. In this example here, I'm showing an input, which you upwards of 50% of the light in order to get different light powers off of one leg versus the other. We can actually shorten that junction or refuse together, and now we can actually go from 50/50 power where one leg has 90% power and the other leg has 10% And these come in various percentages. They can go from 90, ten, 80, 20, 70, 30 and 60/40. Where these optical couplers come into play is an optical tap's. We do something very similar to what we do with the RF taps. We take the optical coupler. In this example, I'm using a 1090 optical coupler. We're taking one leg going from the input to the out, and then we have one down Lake. The down leg in this case feeds a four way splitter, or could be a two or an eight. So with the 9010, now we have the input power of 100% on the output. We have 90% And then on the coupler down leg, that's where we have 10% In this example here we're looking at 80, 20% to 100% in 80% in the output and 20% feeding down to that four way splitter. These are very similar to the RF taps. Where these would be used would be up in the air, on the street, underground, in the street, backyard easements, but we'd have the fiber optic input in one pole and we'd feed the next pole. In this case, we're going from a 9010, 20, 80, 70, 30 and 60/40. Next, we're going to look at multiplexers and dymocks complex. This always reminds me of the Pink Floyd dark side of the moon when I see this. But a multiplex device that combines two or more separate signals for transmission through a single fiber. A d-max flexor allows separation of the signals in the same format as a signal was multiplexed. In this example here, I'm showing a wave, division, multiplex, r and D multiplex are on both sides and in between is an individual fiber. We have two inputs on each of the multiplexer 49ers and the DreamWorks flexors. When we first started using fiber, what we would do is we'd actually take a separate fiber for the forward and separate fiber for the return, and that wasn't very effective when we started looking at today's technology. We need a lot of fiber out there too, in order to be more efficient and cost effective. We're actually going to use these multiplexing. So the way this works is here I'm showing a forward signal in the downstream of 1,550 nanometers. It goes into the multiplexer is injected onto the fiber. Then on the other end, which would be a Dimock complex or we bring the signal back out at 1,550. On the bottom right there. We have a return signal. So this is the upstream 13, 10 nanometers. We put that into the multiplexer on the right now goes on to the fiber to this fiber now has two wavelengths on it. At the time of or now it comes back out at 1310 nanometers. So we're going to have multiple wavelengths or information on one fiber. Very efficient. Very cost effective. With that technology. That brings us to the course wavelength division, multiplexing cw, WDM, this allows up to 18 channels to be multiplexed onto a single fiber. Here I'm just showing an example of some of the wavelengths that you could have. This allows 18 channels available from 1271 nanometers to 1611 nanometers with 20 nanometer cable spacing. To take this one step further. We have dense wavelength, division, multiplexing or WDM, and this allows for 80 channels to be put on to one single fiber. These channels are available from 1530 nanometers to 1565 nanometers with 50 and 100 gigahertz channel spacing. So these are spaced very close together. Let's look at where the CW DM resides versus the CW DM. Here I'm showing 18 CW dam wavelengths in nanometers from 1271 to 1611 nanometers. And now I overlay the TWD DM 80 channels. You can see we can squeeze 80 channels in it to a very small area. Here's our multiplexer multiplex, or again, we can have multiple wavelengths on a single fiber. Again, very effective and efficient. Thanks for joining us on this fiber optic session on transmitters, receivers and fiber optic devices. I'm now going to look at the questions that came in on the chat. I need to switch over to my computer at my desk. So in the meantime, if you have any additional questions, feel free to put them in the chat. All right. Let's take a look at the questions that came in on the chat. We got three or four here. The first question is, you mentioned never to look at the end of the laser output. Does this apply to the leds? And the answer is yes, it does. You know, even though the LEDs are lower power than the lasers. Overexposure can damage the eye. So be very careful. Never look into open end of a fiber or into a connector or anything like that. You know, always follow your company policy when it comes to safety guidelines when dealing with the fiber. And then two optical splitters require power. And the optical splitters are passive devices, just like the RF splitters, you know, they don't need the power. So same with the optical splitters. There's no active devices in there. So it's just all passive. So it does not require power to operate. And then the next one is Why are wavelengths 13, 10 nanometers and 1,550 nanometers always being used in optical communication systems? And with this, this is where these wavelengths have the lowest attenuation to them. And with that, you know, if you look back at our first fiber session that we did the introduction, in theory, we actually covered this. And you can go back there. In fact, you know, we had another question from Damian about if we could actually download this video. And at this time, you can't. But if you go into the link that's provided in the chat, you'll be able to watch this video. And then the other videos in this series are at the bottom of the page. So with that prior question, you can go there, you can look at the first fiber section that we did. And then for this session here, you can watch it again, but yet this time you can't download it. Let's see the. I think that's about it for the questions there. But, you know, hopefully you got something out of this training session. You know, this is the third of the five or six that we're actually doing. And this series here, we're going to be continuing it. So Amphenol broadband solutions, you know, look for reminders of this upcoming session. They'll probably be in a month or so. This is going to be covering part 4. And in this session, Charles Dillard is going to be covering the fiber one series when it comes to fiber to the extra fiber to the home technology. So be sure that you look for the invite for that. And again, it'll be a month of out or so and we look forward to you. Joining us in next session. And again, you know, check that link at the bottom there and you can look at the previous videos and also this one. So, again, Thank you very much and we'll see you next time. Thank you.