A bit about DWDM 400 / 500G, 1Tb, about super channels and the future
Standing next to the tested DWDM 100G, willy-nilly began to read everything that came handy and dug up some material on the prospects for the further development of DWDM technology. Gradually aware of the material, I will publish the results of awareness - perhaps someone will be interested. Only part of the information is published here - it will be continued later.
In the near future, the developers promise us the possibility of transmitting information at speeds of 400 / 500G and even 1TB at one wavelength.
I will designate in two words. DWDM is a spectral channel multiplexing technology. What is the meaning of spectral compaction? Through one fiber-optic cable, you can transmit more than one signal in parallel using different wavelengths of light. There are several technologies for spectral compaction –WDM, CWDM, DWDM, HDWDM. Technologies are characterized by the density of the channels, i.e. how much one channel from the other is on the frequency grid.
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Currently, DWDM and HDWDM systems are of most interest because they provide the ability to transfer the largest amount of information through a single fiber-optic cable. If we consider existing systems, we can distinguish technologies that provide data transmission at a speed of 2.5 / 10 / 40G per channel. Total channels can be created up to 80 or up to 96, it all depends on the manufacturer of the equipment and what frequency grid it uses. Those. the total bandwidth of one optical fiber will be = (80 or 96) * (transmission rate per channel). For example, for a system with 80 channels and a transmission rate per channel of 10G, the maximum speed at which data can be transmitted through a single cable = 10G * 80 = 800G
Currently, most manufacturers are introducing the DWDM 100G complexes to the market, which allow transmitting information at a speed of 100G / s per channel (lambda) and deliver the maximum power of 9.6 Tbit / s. I stood there a little while when I tested these complexes, which I once wrote on Habré (however, I had to hide the post, because testers were outraged - like I’m breaking confidentiality) Puzzled by the 100G problem I wanted to look a little further into the future. What is there?
I think it’s no secret that technologies are being developed in accordance with the requirements of the services market. If you look at the situation at all, you can see that in the future we are waiting for an avalanche-like increase in the high-quality traffic transmission lines. First of all, as I see it, the 4th generation network on LTE, which have actively begun to be built by mobile operators in our country, will be to blame. If we take into account that LTE, even in the trimmed configuration, which is supposed to be implemented in our country, implies up to 80 Mbps of downlink, making a discount on realities and dividing the threatening figure by 8, we get 10 Mbps per mobile terminal. That on average is 5-7 times more than the existing 3g with HSPA +. Yes, I know that the standards contain completely different numbers, but in reality they look something like that. Unfortunately.
So, if our mobile operators think about it, then they will understand that at that moment, when each mobile phone starts to want a speed of 7-15 Mbit / s over the radio channel, the speed of the transport networks will increase. And it will increase until LTE reaches its ceiling. The ceiling for LTE, as I recall, is 400 Mbit downlink.
At some point, the operators will have a question, how to further develop transport networks? Then you have to either lay new optical lines, or put more modern equipment to better use the old ones. If we compare the cost of laying lines and the cost (even if it is the newest DWDM complexes) - I have no doubt that the operator will choose. Hence the relevance of the issue with the development of DWDM technology to speeds in excess of 100G.
Annual studies show that traffic is growing at about 40% per year.
Well, here I come to the most interesting. How will systems with speeds> 100G in the channel be organized, what they will be, etc. But all in order. As far as I was able to figure out, the stages of the development of DWDM technologies up to 400,500 Gbit per super-channel * and 1Tbit are assumed. No other was noticed.
* A super channel is defined as a logical combination of several physical channels, which from the client’s side can be seen as a single channel with a bandwidth of> 100G (400, 500 or 1000 Gbps). Those. if at the entrance you have a client signal in 1Tb you drive it to a special Super-channel line card that processes the client stream to 1Tb and drives it along several carrier channels to the line. Here is the prototype of the 1Tb module from Infinera:
Currently there are no approved standards defining how the super channel should work. As part of the standardization of the super-channel work:
1) Optical Internet Forum, is developing the possibility of expanding its developments in the field of 100G DWDM and incorporating super-channel logic into them
2) ITU-T, in recommendation G.694.1, approved the frequency grid in increments of 12.5 GHz
3) ITU-T SG15, Question 11 - a research question is opened on the development of new containers taking into account the capabilities of the 12.5 GHz frequency grid (developed by Infinera, Finisar, Verizon)
Here, ITU-T proposes to extend the G.709 recommendation and an additional container to frame structures that will allow one OCh to be associated with several optical carriers. The scheme will now look like this:
4) IETF CCAMP develops a Generalized Label for Super-Channel Assignment on Flexible Grid 12.5 GHz, as well as an OSPFTE extension to support GMPLS in a 12.5 GHz grid (developed by Infiner and Verizon)
Thus, in the case of the invention of transponder modules with the possibility of restructuring through 12.5 GHz and a transmission rate of 100G (against the existing 25 GHz, and then only at Infiners), we can get a 2-fold gain in line capacity due to a more dense frequency grid. If we assume that the channel is 100G, then the approximate total data transfer rate to the line can reach 32Tbit / s.
The topic is new, there is not much information, most of the developments are not open to public use - so please take a condescending attitude - it turned out to be incomplete and messy.
In the near future, the developers promise us the possibility of transmitting information at speeds of 400 / 500G and even 1TB at one wavelength.
What is DWDM?
I will designate in two words. DWDM is a spectral channel multiplexing technology. What is the meaning of spectral compaction? Through one fiber-optic cable, you can transmit more than one signal in parallel using different wavelengths of light. There are several technologies for spectral compaction –WDM, CWDM, DWDM, HDWDM. Technologies are characterized by the density of the channels, i.e. how much one channel from the other is on the frequency grid.
What systems are there now?
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Currently, DWDM and HDWDM systems are of most interest because they provide the ability to transfer the largest amount of information through a single fiber-optic cable. If we consider existing systems, we can distinguish technologies that provide data transmission at a speed of 2.5 / 10 / 40G per channel. Total channels can be created up to 80 or up to 96, it all depends on the manufacturer of the equipment and what frequency grid it uses. Those. the total bandwidth of one optical fiber will be = (80 or 96) * (transmission rate per channel). For example, for a system with 80 channels and a transmission rate per channel of 10G, the maximum speed at which data can be transmitted through a single cable = 10G * 80 = 800G
Currently, most manufacturers are introducing the DWDM 100G complexes to the market, which allow transmitting information at a speed of 100G / s per channel (lambda) and deliver the maximum power of 9.6 Tbit / s. I stood there a little while when I tested these complexes, which I once wrote on Habré (however, I had to hide the post, because testers were outraged - like I’m breaking confidentiality) Puzzled by the 100G problem I wanted to look a little further into the future. What is there?
Prerequisites for the development of technology.
I think it’s no secret that technologies are being developed in accordance with the requirements of the services market. If you look at the situation at all, you can see that in the future we are waiting for an avalanche-like increase in the high-quality traffic transmission lines. First of all, as I see it, the 4th generation network on LTE, which have actively begun to be built by mobile operators in our country, will be to blame. If we take into account that LTE, even in the trimmed configuration, which is supposed to be implemented in our country, implies up to 80 Mbps of downlink, making a discount on realities and dividing the threatening figure by 8, we get 10 Mbps per mobile terminal. That on average is 5-7 times more than the existing 3g with HSPA +. Yes, I know that the standards contain completely different numbers, but in reality they look something like that. Unfortunately.
So, if our mobile operators think about it, then they will understand that at that moment, when each mobile phone starts to want a speed of 7-15 Mbit / s over the radio channel, the speed of the transport networks will increase. And it will increase until LTE reaches its ceiling. The ceiling for LTE, as I recall, is 400 Mbit downlink.
At some point, the operators will have a question, how to further develop transport networks? Then you have to either lay new optical lines, or put more modern equipment to better use the old ones. If we compare the cost of laying lines and the cost (even if it is the newest DWDM complexes) - I have no doubt that the operator will choose. Hence the relevance of the issue with the development of DWDM technology to speeds in excess of 100G.
Annual studies show that traffic is growing at about 40% per year.
DWDM systems with speeds> 100G
Well, here I come to the most interesting. How will systems with speeds> 100G in the channel be organized, what they will be, etc. But all in order. As far as I was able to figure out, the stages of the development of DWDM technologies up to 400,500 Gbit per super-channel * and 1Tbit are assumed. No other was noticed.
* A super channel is defined as a logical combination of several physical channels, which from the client’s side can be seen as a single channel with a bandwidth of> 100G (400, 500 or 1000 Gbps). Those. if at the entrance you have a client signal in 1Tb you drive it to a special Super-channel line card that processes the client stream to 1Tb and drives it along several carrier channels to the line. Here is the prototype of the 1Tb module from Infinera:
Currently there are no approved standards defining how the super channel should work. As part of the standardization of the super-channel work:
1) Optical Internet Forum, is developing the possibility of expanding its developments in the field of 100G DWDM and incorporating super-channel logic into them
2) ITU-T, in recommendation G.694.1, approved the frequency grid in increments of 12.5 GHz
3) ITU-T SG15, Question 11 - a research question is opened on the development of new containers taking into account the capabilities of the 12.5 GHz frequency grid (developed by Infinera, Finisar, Verizon)
Here, ITU-T proposes to extend the G.709 recommendation and an additional container to frame structures that will allow one OCh to be associated with several optical carriers. The scheme will now look like this:
4) IETF CCAMP develops a Generalized Label for Super-Channel Assignment on Flexible Grid 12.5 GHz, as well as an OSPFTE extension to support GMPLS in a 12.5 GHz grid (developed by Infiner and Verizon)
Thus, in the case of the invention of transponder modules with the possibility of restructuring through 12.5 GHz and a transmission rate of 100G (against the existing 25 GHz, and then only at Infiners), we can get a 2-fold gain in line capacity due to a more dense frequency grid. If we assume that the channel is 100G, then the approximate total data transfer rate to the line can reach 32Tbit / s.
The topic is new, there is not much information, most of the developments are not open to public use - so please take a condescending attitude - it turned out to be incomplete and messy.
Source: https://habr.com/ru/post/143261/
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