#aroundcable

[teardownit]

Which reflectometer to choose for new fiber-optic lines?

Modernization of 100/400G networks and deployment of 5G networks at the proper quality level require testing of optical fiber communication lines (OFC). Choosing the right methods and additional instruments is critical when conducting bulk testing, as mistakes can be very costly.

If we talk any modern optical networks, fiber and coupling quality are critical. Modernization of existing networks involves checking their condition as well as laying new OFCs—testing the quality of connections. The higher the speed of fiber-optic lines, the more stringent the requirements for the quality of their diagnostics. And here the problem of choosing a testing methodology arises: for example, is "testing to the maximum" using bidirectional tests always the best option?

Bidirectional testing of OFCs with a reflectometer: the answer or new problems?

It is important to understand that fiber-optic communication is related to reflectometry. Without a high-quality optical reflectometer (OTDR), it is impossible to create a reliably operating fiber-optic link. The solution to the problem of testing comes down to the correct initial selection of equipment and determining the most suitable methodology.

There are two main methods of reflectometry: one-way (one compensation coil at one end of the line; launch cable box) or two-way (Bi-dir OTDR, with a compensation coil at the near end and the same at the far end). .

The direction of the emitted light can influence the test results. In any fiber, there is a difference in the return loss coefficients, and in one particular direction, the light loss may be greater.

Single-sided OTDR testing can miss many anomalies. Wire junctions with different return loss values can compensate for the signal loss in one orientation and attenuate it in the other. In addition, there are dead zones in which the OTDR does not record events.

The figure below shows an example of the difference in signal loss depending on the measurement direction. One side of the testing even shows a negative loss of -0.3 dB, which is, of course, impossible. In this case, an amplification effect is observed due to the difference in the backscatter coefficient (BSC) at the junction of the two cables.

Therefore, one-way OTDR testing is better suited for simple tests such as finding and locating fiber breaks and bends, assessing total signal attenuation in fibers, testing connectors, etc. In this case, there is no need to waste time on bidirectional testing. The main advantage of unidirectional fiber-optic testing is that it is enough to inspect and clean the fiber just once for any one line. This is important since contamination of the connectors can lead to failure of the fiber-optic line, which was working properly before testing. Sometimes customers insist on two-way "full testing," but this can be excessive and even harmful as it introduces an unnecessary risk of damage while cleaning the optical connectors.

Bidirectional fiber inspection without running around

One-sided tests are not accurate when laying new lines and monitoring the performance of FOCs. In such cases, industry standards require bidirectional testing with an optical time domain reflectometer (Bi-dir OTDR) measuring the signal at both ends of the line. This is necessary to identify anomalies that are not detected by conventional one-way reflectometry. In addition, there are unique cases where a line uses cables with different fiber diameters, where bidirectional effects can be important. Bi-dir OTDR testing makes it possible to average the measurement parameters and give a clear assessment of the quality of the fiber-optic link. Ultimately, it is possible to unambiguously determine whether the tested line supports high-speed data transfer. This saves time and money that the customer may lose if the cable system fails on launch.

Traditional bidirectional testing of fiber-optic links implies first measuring one side:

And then testing the optical line on the other side:

Then obtain the average parameters. This is an important job that requires manual data processing. It can be accelerated by using two similar instruments with two external cable routes simultaneously (the bidirectional reflectometer technique), but this requires additional equipment expenses.

Another effective technique is testing with an optical reflectometer with a closed circuit (loopback). This method involves using a reflectometer at one end of the line and a reference fiber loop at the other. This way, one can test two optical lines in both directions, alternately swapping cables. This is the most effective method in terms of cost and labor savings since it requires only one reflectometer, loop switching, and two compensation coils.

A major drawback of OTDR-loopback testing is the labor-intensive process of recording and merging test data. Often, manual work with data leads to errors, and repeated tests are needed. This problem has been solved in modern optical reflectometers, such as the VIAVI T-BERD/MTS-4000 V2.

When using such advanced devices, the task of specialists is reduced to the high-quality implementation of procedures for cleaning contamination of optical connectors and one-way checking of launch cables before starting bi-directional testing.

Thus, preference should be given to OTDR modules and platforms that offer the ability to choose any optical cable diagnostic technique with maximum automation. This choice should be made based on practical needs and not on the capabilities of existing equipment. Ultimately, this approach reduces the likelihood of OFC failures.

[talk-with-sebastian]

“let go-“

*he wiggled his tail tip aroundc trying to get him off*

“no sushi- bad Allo-“

@unda-pressure

Can you do it /nf

(Sorry if this makes anybody uncomfortable /gen)

"id let Allo do it... I MEAN WHAT-"

[ierogenvy]

if u work in hr and therefore have an office that u are in all day why the hell cant u answer the phone that is in ur office

[freckledbastard]

not to be needlessly repetitive or anything, but i was checking over the original japanese chapters for 913 and 914 again (when kiku is first seen and when she introduces herself as a samurai), and you know how people are always like “oh she uses sessha, which is for male samurai”? 1, as we’ve already said it’s a term for any samurai, its just that most samurai were men.

and 2, the first time she uses it she just says せっしゃ (sessha, without the kanji). this is what zoro and luffy are reacting to. kiku, who as far as they know is only the poster girl for the tea house is suddenly using the same pronoun as the samurai they know. once she starts chasing after tama is when she uses sessha again, but this time as 拙者 (sessha, with the kanji), its a confirmation both to zoro and luffy, as well as the audience that she’s a samurai, she’s not just using it wishy washy.

japanese language in one piece can be pretty interesting though. like how perona is all about cuteness, but apart from using ‘watashi’, her use of language is literally as crude as luffy’s, it’s excellent. 

[saporietoys]

#napoli #sundaynight #lifestyle #instagram #followme #love #girls #likeback #women #blogger #aroundcity #friends #wine #beer #cocktails Buona serata. (presso Archivio Storico)

[chikkou]

DONT FUCKING PLAY GAMES WITH ME IM NOT FUCKING AROUNDC OYU SON OF A BITCH

[samarasshoesart-blog]

"Sun-day" (A few hours before with a friend) #athenscity #spring #sun #happypeople #coffetime #sunday #friends #cityview #gr #athina #greece #join #hellas #aroundcity #point #center #myshoes #view #stepside #mylook #today #coffeshop #central #look (στ��ν τοποθεσία Γιασεμί - Yiasemi) https://www.instagram.com/p/BwhzBsSnqCy/?igshid=1pxlsw1n9jfdl

[simo-xoxo]

Ecco come vorrei passare la domenica: a bere chai tea latte passeggiando per le strade di Manhattan 😭 #memories #takemeback #nyc ________________ #manhattan #ny #nycstreet #nystreetstyle #progettocinque #aroundcity #travel #travelblogger #travelphotography #travellist #travellover #lovethis #takemebacktonyc #missthisplace #starbucks #coffeetime #sunday (presso New York, New York) https://www.instagram.com/p/Bt-wzW5Hg7W/?utm_source=ig_tumblr_share&igshid=1dh6ditmjn5d8

[teardownit]

Best budget-friendly optical reflectometer

In recent decades, the rapid development of optical fiber communication (OFC) lines has required simple, reliable instruments for diagnosing optical communications. An optical time domain reflectometer (OTDR) is one of the most common devices for testing fiber optic links and identifying problem areas in fiber optic communication lines. What criteria should be used to choose a reflectometer so that it performs correctly and does not require excessive financial investments?

Reflectometer: luminous intensity

A reflectometer directs a beam of laser light into an optical fiber. Then, it measures the parameters of the reflected light, thus analyzing the characteristics of the optical fiber. This way, one can not only detect but also determine the location of any damage to the fiber optic line: a lousy receptacle or connector, a cable bend, light loss, poor splicing, etc.

This is a very effective technology, but it has two severe limitations. First, the reflectometer's probe pulse is reflected from all connectors, including the first one, which is why "lighting" creates a dead zone in which measuring is impossible. This problem is solved using an additional piece of optical fiber (launch cable) connected to the line under test. The dead zone is on this fiber, and the entire line can be tested. It is necessary to consider the length of the line that is supposed to be tested and select the correct length of the compensation coil; sometimes, the length can reach several miles.

The second limitation is that different types of optical fiber have the highest light reflectance coefficient at different wavelengths. Of course, the best choice seems to be the most versatile device that can operate in a wide range of wavelengths, for example, from 850 nm to 1650 nm. In particular, the VIAVI MTS-8000 universal measuring platform and a set of modules capable of solving almost any problem of fiber-optic communication analysis.

One must keep in mind that expanding the capabilities dramatically increases the cost of the device. However, these capabilities are not always necessary. More straightforward solutions are often sufficient for checking and even last-mile optical line certification, such as an optical reflectometer with the tester function and damage visualizer Greenlee 930XC-20C-UPC-FC.

The situation is similar to the dynamic range—the strength of the reflectometer signal and its ability to detect even slight attenuation of the optical signal. This can result in a severe deterioration in the efficiency of fiber optic lines on long, critical lines. Therefore, more expensive reflectometers with a wide dynamic range are used to check them. Generally, an OTDR with a dynamic range of 6 dB is more excellent than the loss of the longest optical communication line that the OTDR will ever have to service, which is sufficient for reliable testing.

These are the main aspects to consider first when choosing a reflectometer. However, many reflectometer models are on the market, and selecting them is not always easy. Fortunately, there is a simple set of questions, and answering them will give you a "portrait" of the device best suited for a specific set of tasks.

The right questions to ask when choosing an optical reflectometer

First of all, you need to answer questions about using your new reflectometer:

What networks and types of optical fiber will be tested (for example, multi-mode optical fiber or single-mode optical fiber)?

What is the maximum length of the fiber-optic link to be tested?

What measurements are aimed at (certification, troubleshooting, regular maintenance)?

The answer to these questions will significantly narrow the field of suitable reflectometers. For example, 850 nm and 1300 nm wavelengths are used for multi-mode optical fiber, and 1310 nm and 1550 nm are used for single-mode optical fiber. In the case of PON testing, wavelengths of 1490 nm and 1625 nm may be needed in addition to 1310 nm and 1550 nm.

If the reflectometer's main task is to localize damage, then buying an expensive device may be a waste of money.

However, if detailed diagnostics of a fiber-optic link and its certification are needed, professional reflectometers with a large dynamic range, small dead zones, and good software for processing reflectograms and generating a report are necessary.

It is also necessary to consider the aspects related to the device's operation. In particular, the size and weight of the reflectometer are directly related to the team's mobility. Devices with a larger screen (more than 5") are most often chosen for indoor work or as part of a mobile lab. Specialists use portable devices to work on city networks. Such devices must have waterproof housing and withstand a wide range of operating temperatures.

The minimum operating time on one battery charge is preferably at least 8 hours so that field measurements do not extend over two working days. The ability to upload data to the cloud for subsequent analysis and results processing will significantly save time.

Often, several instruments can be combined in one housing: a reflectometer, a tester, a damage visualizer, an optical spectrum analyzer, a dispersion analyzer, etc.

An important feature is the ability to expand the functionality and update the reflectometer software during operation, which means that a more expensive modular solution may be a more profitable purchase in the long term in some cases.

[lifebigjourney]

Oh yes! I hitchhiked more then 3000 km, slept 2 night in tent at 2 crazy and really cold nights and now I am in Irkutsk city. If you know - Baykal lake it's nearby. Amazing experience! Have a good day my friends!😜✌️ ---------------------------------- Догадайтесь в каком городе я сейчас? Конечно же, это Иркутск - ответ прямо на фото. 3 дня я ехал автостопом, прошёл более 3 тыс км, две жуткие холодные ночи в платки, парочка десятков людей и я в Иркутске. Тёплая, уютная квартира, душик, нормальная еда. И, спасибо Паша за приём! А пока я погуляю пару дней в этом замечательном городе. Он мне уже успел понравиться. Всем отличного дня!😜✌️ ___________________________________ #Lifebigjourney #DenisBashmakov #dharma_travel #бродягидхармы #tpsfotostation #traveler #блоггер #hitchhiking #travel #iamtb #journey #путешественник #чуваш #сыбайскийпарень #gf_streets #Россия #iaminrussia #russia #явроссии #автостопомпороссии #автостоп #иркутск #ялюблюиркутск #irkutsk #baykal #сердце #добро #прогулка #aroundcity (at ТРК "Модный Квартал")

[absmarthealth]

Youth Fitness Trainer Certification - $ 69.99

Youth Fitness Trainer Certification – $ 69.99

What are three characteristics of a youth trainer? a) Good communication skills, timeliness, and an upbeat attitudeb) Being physically fit, being good looking, being fun to be aroundc) Funny, being organized, being creatived) Being physically fit, having the ability to listen, being strict so youth pay attention Answer: a What are three fitness based tests that you can perform with your…

[easy-breezy-b2utiful-monbebe]

I have a confession to make. I started watching a kdrama *gasp* I know... it's been a while I just hope I keep watching and not just watch the first few episodes and forget about it... anyways I started watching "I'm Not a Robot" it is pretty funny and each episode is only 30 minutes!!

I had seen several posts and I honestly thought it would be about an introvert so I was like, yeahhhh introvert person! Must watch... but nahhh It is a really interesting and funny drama so I hope I stick aroundc:

[arflorez]

🍃☁️ #Nature #Fog #Clouds #Green #Cold #Weather #Stones #AroundCity #Trees #Road #Bicycle #Rocks #Flowers #Leaf #Cloudy #Overcast #Nublado #Niebla #Frío #Colombia

[simo-xoxo]

Buongiorno ragazzi! Finalmente è uscito il video sul mio viaggio a New York. Potete vederlo sul mio canale #youtube , il link lo trovate in bio! Have a nice day! ☀️ #youtubeitalia #newyork #vlog ———- #nyc #ny #video #newvideo #youtubevideos #youtuber #towatch #look #lookat #manhattan #brooklyn #city #view #aroundcity #travelpic #statueofliberty #memories #travelmemories (presso Statue Of Liberty, Liberty Island, New York City) https://www.instagram.com/p/BtN7h_in7Xi/?utm_source=ig_tumblr_share&igshid=ikwm2li63o2i

[cyan-cat-dubstep]

Belle: hold on a second zone *a purpley red glow covers a finger and lightly touches it to zone, using some of my power to key zone speak out loud with telepathy* so what is wrong with the treeangle then? | tidal: *yawns waking up, still sprawled our in chills head and looks aroundC letting out a shocked squeak when war and buzzy re-enter the water cave*

Buzz jumps through the opening with a victorious holler.

“GUESS WHO PILFERED SOME PIZZA!”

Sure enough, War came climbing in with several boxes of pizza, all suspended in waterproof, red bubbles.

“It was a hassle,” she hummed. “But we managed. The poor shape didn’t even see it coming.”

Chiptune face palmed.

“PLEASE don’t tell me you shattered someone.”

Buzz laughed, “OF COURSE WE DID!”

[teardownit]

Color space basics for HDMI video

There are two general measures of video perception: resolution and color. Those notions are intentionally vague for the purpose of explaining their relation to HDMI transmission.

I've covered the resolution part in previous posts, as this metric is simpler to quantify. Every screen has a limited number of pixel dots; the more, the better. The same logic works for refresh rate; the faster we change the image on the screen, the smoother the motion picture. Screens are rectangular matrixes of pixels with a small number of aspect ratios (roughly, from long 21:9 to square-ish 3:2) and resolutions of 1, 2, 4, 5, or 8K. Higher HDMI standards support more Ks. Thanks to Steve Jobs' legacy, we have the upper limit for the density and, consequently, the number of usable pixels, known as 'Retina'.

The second part, color, is more a matter of taste and perception. Much like audio, there's always a place for debate on compressed vs. lossless and the number and range of color or audio frequency levels. So, let's review color-related terms one by one.

Color space

Color space is basically a color wheel from any color picker window in the software of one's choice. Just arranged in a more scientific, yet two-axis planar pattern. This half-parabolic rainbow-colored thing, called the 'cromaticity diagram', was introduced in 1931 and is still referenced today as a space for all the colors, not counting their luminocity.

Then there's 'color models', a system with a multi-letter name for representing a set of colors (color gamut). The ultimate goal for color models is to cover the color space, but in reality, all the RGBs and CMYKs try to cover the most of the color gamut (or technically possible with the technology they are made for).

RGB

One of the most known color models is RGB. I intentionally don't make any distinction between all the variations of RGB (sRGB, AdobeRGB, and xRGB), as this makes no difference for today's topic. RGB, as the name suggests, is copying the human eye's cone cells that make any color a mixture of red, green, and blue.

RGB is the go-to format for PCs, monitors, and most image processing activities. Specifically, sRGB is the standard for web images.

The channels, R, G, and B, are represented as three 8-bit numbers, 0 to 255. Some models can use more raw data to get more chrominance levels—16 bits per channel or 48 bits per pixel. So should we aim to use as many bits per pixel as we can? Well, no, it's not practical. A 24-bit Full HD RGB image takes 1920 × 1080 × 24 = 5.93 MiB of space (or 11.87 MiB for a 48-bit one). It seems manageable, but if we consider a minute of FullHD 30 fps 24-bit video, it will occupy 10.43 GiB of storage, which is obviously too much even for modern networks (that's 938 GiB for a 90-minute movie).

There are two ways to mitigate this: either to use compression algorithms like Youtube's H.264/H.265 or to use a better color space to use less data for better results. In terms of RGB, one could use a limited set known as R'G'B' with values of 16 to 235.

CMYK

Worth a quick mention. It has no use in HDMI video transmission as it is made for printed physical products.

YUV, YPbPr, and YCbCr

Those are used interchangeably, although they differ slightly. But all we care about here is the general idea. YUV works best for photo and video content. Human eyes perceive images as a combination of luminance and color. The luminance is the most important part; black-and-white images are enough for us to have a pretty good idea of what's shown in the image. In the dark, we see just black and white, as there's no light to reflect from colored objects, and it's fine.

So the idea is to devote one color channel to luminance alone and the other two to color: red (or red-difference) and blue (or blue-difference). YCbCr can be converted to and from RGB with a matrix. But the levels of the components Y, Cb, and Cr are gamma-corrected, meaning they are non-linear. When RGB has the same steps for color channels, luminance and, subsequently, red and blue-difference channels don't work like that. Levels of luminance are perceived in a more complex pattern; the white part of the spectrum should have fewer steps, and the dark part needs more.

This attention to luminance levels brings us to HDR.

HDR

HDR stands for high dynamic range, as opposed to SDR, which stands for standard dynamic range. Wider range means more bits for the channels (usually 10 or 12), higher maximum luminance levels, and more metadata for the display.

That means that the number of luminance steps (the same goes for both chromatic channels) increases; the maximum luminance level is an order of magnitude greater than in SDR. In addition to raw data, there's metadata for monitor settings. All the screens are built differently in terms of color calibration and maximum peak brightness. The source communicates luminosity and contrast values to the display for it to adjust. HDR was introduced in HDMI 2.0 as 'static HDR', meaning it sends one set of metadata for the whole video stream. HDMI 2.1 can use 'dynamic HDR', sending different metadata for every scene. HDR is a well-known, widely marketed feature that really elevates the user experience. Dynamic HDR is usually titled 'HDR10+' on the box (compared to static 'HDR10').

Here lies the answer to the question some people ask, "Is 10-bit color ('deep color') HDR?" No, it is not. 10-bit color in RGB means more steps for chromatic channels, not an extra-wide range of luminance. Should YCbCr HDR always take upwards of 10 bits per channel? Yes, 10-bit color could be HDR or SDR, but an HDR signal is 10-bit or more.

Chroma subsampling

The last part is subsampling. It is a third middle option between using compression or implementing a limited color model. Chroma subsampling is used for YCbCr to keep luminance data, as it is the most precious for us, and compress individually colored pixels into bigger blocks.

A standard sample is a two-row block of pixels, usually 4×2. Subsampling is represented as numbers J:a:r.

The first digit 'J' of 4:4:4 or 4:2:0 represents the number of pixels in a row. Basically, it's always 4.

'a' represents the number of different colors (chromatic samples) in the first row. Can be treated as a horizontal resolution; do we reduce the 4 pixel colors of the first row to '1', '2', or do we keep all '4'?

'r' is the number of color changes between the first and second rows. This is a vertical resolution and can be either '0' (no difference; the second row has the same chrominance as the first one) or 'a' (there is a difference in color between two rows).

So, 4:4:4 means no subsampling; 4:2:2 or 4:4:0 reduces 8 different colors to just 4; 4:1:1 or 4:2:0 reduces the number of colors to 2 (vertically or horizontally). Practically useful numbers are 4:4:4 and 4:2:0, as they are the most common.

In conclusion, different color spaces are made for different applications. A PC monitor with SDR works best with RGB for displaying pixel-perfect text on flat surfaces. YCbCr is meant for non-productivity applications like photos, movies, or videogames. YCbCr with no subsampling is great for everything; 4:2:0 is visually indistinguishable from perfect when watching movies and sports.

HDR should always be 10-bit; there's no 8-bit HDR and never was.

All this makes sense for units with HDMI version 2.0 and higher, and there's no point in talking about color spaces in previous versions.

‍====== Eugenio S