Fibre optic cabling is often known for its extremely high speeds but is there anything that may develop delay issues in transmission via fibre optic cabling?
Electronic – What are the different possibilities for delay distortion in fibre optic cabling
cablesdelayoptical-fibre
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No, you do not need to do anything special. We have X-ray generators and Digital Imaging devices everywhere at my place of work, we run cable around them, in front of them sometimes(tie comes loose) and all around them. We have never had issues.
Other forms of radiation can have very negative affects on materials and electronics, but on ethernet cable we do not see negative affects from these either.
X-Rays are not that terrible, it is just not a good idea to get a dose from them repeatedly throughout the day. This is why the therapist is placed behind a bit of lead.
I2C is in some ways a very neat protocol, but its design purpose is to interconnect devices on a single board. Even beyond issues of signalling levels, there are some protocol issues as well which may pose problems when using it for multi-board communications.
For example, suppose that two slave devices are connected that would both allow a master to read an arbitrary number of bytes, and which may return zero for an arbitrary number of those bytes. If while one device is sending data to the master a second device mistakenly interprets part of the data as a "START" sequence followed by its read address, it would be possible that for every clock cycle thereafter at least one of the devices would be wanting to output a "0" data bit. Such a scenario would make it impossible for the master to ever regain control of the bus. While it's possible to design single-board communications such that stray pulses "just won't happen", that's often not feasible when connecting many devices. One may try to minimize the likelihood of stray pulses occurring, but should not expect to avoid them totally. Having a sensor reading get corrupted once a month because of a stray pulse may be acceptable, but having the system lock up once a month would likely be less so.
If you're using a single-master setup, I would suggest that it may be worthwhile to use separate wires for SDA out to the slaves and SDA return. If the slaves are using handshaking, it may be worthwhile to do likewise for SCK. The master's output could then be driven actively high and low (rather than being actively driven low and passively pulled high). If the connectors had designated "in" and "out" sides, each board in the chain could "AND" the return from the previous device with the pin state of its own device, and output active high-and-low in the return direction as well. Such a design would likely require use of a bit-bang master rather than a hardware master, but given that software-master implementations can often manage better error recovery than hardware masters that shouldn't be much of a limitation.
In addition to the improved robustness resulting from active-high/active-low drive, using separate output/return wires for SDA will avoid the possibility of one slave device interfering with the master's attempts to get another device to shut up, since even if all but one slave device wanted to output low on SDA, the master would have no problem generating a low-to-high transition on the SDA pin of the last remaining slave.
If you don't want to use the extra wires to separate SDA out from SDA return, it would be possible to wire the slaves so that their pull-down strength on SDA was limited, and wire the master so that it could safely overpower the slaves. That would allow clean recovery in case of slave malfunction, but would not offer the signal-cleanliness advantages of using separate wires. Further, it would only work well if handshaking is not used. Robust I2C operation requires that transitions on SCK and SDA be separated by a time in excess of the worst case transmission skew. If the master is in sole control of SCK, it can ensure that. Slaves which use handshaking, however, may asynchronously generate events on SCK and SDA, with no way for the master to control their separation.
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The primary limitation of the signal bandwidth of optical fiber is dispersion. Dispersion, as the term is used in fiber optics, is when one component of the signal propagates faster than another component. This leads to narrow input pulses stretching in duration as they propagate along the fiber, causing the fiber to act as a low-pass filter on the signal.
The main forms of dispersion are
modal dispersion: When the different waveguide modes of multimode fiber propagate at different speeds along the z axis of the fiber. Modal dispersion is why multimode fiber has lower bandwidth-distance capability than singlemode fiber.
chromatic dispersion: When different wavelengths propagate at different speeds due to the material properties of the glass.
polarization mode dispersion: When different polarizations of light propagate at different speeds due to slight imperfections in the symmetry of the waveguide (or due to deliberately induced asymmetry in polarization-maintaining fiber).