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Cape Town water crisis
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Graph of total reservoir water stored in the Western Cape's largest six dams from 30 June 2013 to 15 January 2018. The graph illustrates the declining water storage levels over the course of the Cape Town water crisis. Data obtained from the Climate Systems Analysis Group (CSAG)
A drought in the Western Cape province of South Africa began in 2015 and is resulting in a severe water shortage in the region, most notably affecting the city of Cape Town. With dam levels predicted to decline to critically low levels, the city announced plans for "Day Zero", when the municipal water supply will largely be shut off, potentially making Cape Town the first major city to run out of water.[1][2][3] Through water saving measures and water supply augmentation, by March 2018 the City had reduced its daily water consumption by more than half to around 500 million litres per day, resulting in the initial prediction of Day Zero in April 2018 being pushed back to 2019. The situation however remains severe, particularly if the run of record dry winters continues through 2018.
Contents
[hide]
1 Background
2 Causes
3 Timeline
3.1 2015-2016
3.2 2017
3.3 2018
4 Severity of the drought
5 Impact
5.1 Public health
5.2 Occupational health risks
5.3 Vulnerable population
5.4 Industry
5.5 Hydrological poverty
5.6 Political
5.7 Positives
6 Solutions
7 References
8 External links
Background[edit]
The Cape Town region experiences a Mediterranean climate with warm, dry summers and winter rainfall. Water is supplied largely from the six major dams of the Western Cape Water Supply System in mountainous areas close to the city.[4] The dams are recharged by rain falling in their catchment areas, largely during the cooler winter months of May to August, and dam levels decline during the dry summer months of December to February during which urban and agricultural water use increases.
Cape Town's population has grown from 2.4 million residents in 1995 to an estimated 4.3 million by 2018, representing a 79 percent population increase in 23 years whereas dam water storage only increased by 15 percent in the same period.[5] In 2016/2017, 64.5% of the city's water supply went to formal residential users, while 3.6 percent went to informal settlements.[6]
The possibility of the city exceeding its water supply was highlighted as early as 1990.[7]
From 1950 to 1999, the city's consumption of treated water grew at 4% per year in line with the city's population growth. Water consumption peaked in 1999 at 335 million cubic metres (335 gigalitres) per year. In 2000 a plan called Africa Water Vision 2025 was developed aiming for "equitable and sustainable use of water for socioeconomic development".[8]
Periods of low winter rainfall in 2000/2001 and 2003/2004 resulted in water restrictions being imposed.[9][10] In 2007, the city implemented a 10-year water demand management strategy, which has successfully kept the annual consumption at or below the 1999 level despite ongoing population growth.[9]
In 2009, the storage capacity of the dams supplying Cape Town was increased by 17 percent from 768 to 898 million cubic metres through the completion of the Berg River Dam.[11] Despite the increased storage capacity, the Department of Water Affairs and Forestry predicted that the growing demand from the city would exceed supply by 2013 without water conservation and demand management measures by the city, and that even with those measures, further water sources would be required by 2019.[12]
Causes[edit]
The cause of water loss in Cape Town has been debated. While drought is a factor in the city’s water scarcity, the degree of drought has been questioned. It is believed water scarcity, caused by the drought, is being exacerbated by population growth, potentially unreported agriculture use, invasive species, and poor planning of water management. Cape Town particularly has grown by 50 percent in the last decade.[13]
While rainfall tends to undulate at stations monitoring rainfall where water is stored for Cape Town, there has been a clear, significant drop in 2016.
A study conducted by the Climate System Analysis Group at the University of Cape Town ran statistical analyses to determine that rainfall between the years 2015 and 2017 was very rare and severe.[14]
Some scientists believe this once in a millennium drought is being exacerbated by climate change with a one degree celsius increase in temperature over the past century. Models predict Cape Town will increase another 0.25 degrees celsius in the next ten years, which would increase drought likelihood by up to seven times. Previous climate modeling suggested a likely decrease in rainfall due to climate change, and this is likely some of the first evidence supporting the model. There is additional concern that several other cities will follow suit behind Cape Town in water scarcity.[15]
A major problem with Cape Town’s water dependence is that their water systems were built on the stable climate of previous years. Climate change has changed precipitation patterns in the area, leading to less stable sources of water and a quicker rate of water loss than previously expected. Another large cause of water scarcity is agriculture use, which consumes 80 to 90 percent of the area's water. In 2016, Cape Town exported 113 million gallons of wine to Europe and the US. For each gallon of wine, between 666 and 1,357 gallons of water is used. One third of the water exported through the wine industry could be used for the 7 million people without access to water in South Africa. In addition, Cape Town exported roughly 231,000 tons of citrus fruits in 2017, resulting in an additional exportation of roughly 30 billion gallons of the area’s water.[16]
Timeline[edit]
Water levels as a percentage of total dam capacity by year.[5]
Major dams
9 April 2018[17]
15 May 2017
15 May 2016
15 May 2015
15 May 2014
Berg River Dam 43.2 32.4 27.2 54.0 90.5
Steenbras Lower 38.4 26.5 37.6 47.9 39.6
Steenbras Upper 75.3 56.7 56.9 57.8 79.1
Theewaterskloof Dam 10.5 15 31.3 51.3 74.5
Voelvlei Dam 14.3 17.2 21.3 42.5 59.5
Wemmershoek Dam 44.1 36 48.5 50.5 58.8
Total stored (megalitres) 192 741 190 300 279 954 450 429 646 137
Total % Storage 21.5 21.2 31.2 50.1 71.9
2015-2016[edit]
After good rains in 2013 and 2014, the city of Cape Town began experiencing a drought in 2015, the first of three consecutive years of dry winters brought on by the El Niño weather pattern and climate change.[18] Water levels in the city's dams declined from 71.9 percent in 2014 to 50.1 percent in 2015.[5] Water restrictions, in place at "Level 1" since 2005, were increased to Level 2 on 1 January 2016 and to Level 3 on 1 November 2016.
Significant droughts in other parts of South Africa ended in August 2016 through heavy rain and flooding in the interior of the country,[19] but the drought in the Western Cape remained.
2017[edit]
Water restrictions were increased to Level 3B on 1 February 2017.
By the end of the dry season in May 2017, the drought was declared the city's worst in a century, with dams having less than 10 percent of their usable capacity.[20] Level 4 water restrictions were imposed, limiting the consumption of water to 100 litres per person per day.[21]
In June 2017 a significant storm hit the area, dropping up to 50 mm of rain, but not enough to break the drought.[22] Overall rainfall in 2017 was the lowest since 1933.[23]
A map of Cape Town's major dams.

With the dry summer season approaching, the city increased its existing water restrictions to Level 4B on 1 July 2017, and to Level 5 on 3 September 2017, banning most outdoor and non-essential use of water, encouraging the use of greywater for toilet flushing, and aiming to limit the per capita water consumption to 87 litres per day, for a total of 500 million litres per day.[24]
By early October 2017, following a low rainfall winter, Cape Town had an estimated five months before water levels would be depleted.[25] In the same month, the City of Cape Town issued an emergency water plan to be rolled-out in multiple phases depending on the severity of the water shortage. Phase 1 was "water rationing through extreme pressure reduction" which involved temporary water cuts and rationing. Phase 1 was implemented immediately with unannounced water cuts to a number of outlying neighbourhoods. In Phase 2 water will be shut off to most of the system except to places of key water access. Phase 3 is the point at which the city can no longer draw water from surface dams in the Western Cape Water Supply System and there is a limited period of time before the water supply system fails.[26]
In mid-October 2017 the City was criticised by water desalination companies for the slow pace of contract negotiations, high level of bureaucracy, lack of urgency, and the inadequate scale of the proposed water supply projects.[27] On 26 October 2017 it was announced that the Cape Town city manager would be given special powers to take drought-related actions that would not have to follow the city's normal decision making and approval process. This announcement came after a review of the city's decision making processes that found "certain aspects of the Preferential Procurement Policy Framework Act, the Municipal Finance Management Act and Supply Chain Management regulations, as well as the council's own Supply Chain Management Policy, failed to adequately provide for the City of Cape Town to 'deal effectively and timeously' with the disaster."[28]
2018[edit]
Theewaterskloof Dam at approximately 12% on 10 February 2018
Level 6 restrictions were imposed on 1 January 2018, and Level 6B on 1 February 2018, limiting consumption to 50 litres per person per day.
On 24 January 2018, the Western Cape provincial cabinet stated that it was the responsibility of the national government to fund the expansion of the water system as the "provision of bulk water supply is a national government mandate." The provincial cabinet also announced that it was drawing up plans with the South African Police Service for a strategy to deploy officers at water distribution points across the city after day zero.[29]
In mid-January 2018, Cape Town Mayor Patricia de Lille announced that the city would be forced to shut off most of the municipal water supply if conditions do not change. "Day Zero" would be declared when the water level of the city's major dams reached 13.5%, and Level 7 would be declared, with municipal water supplies largely switched off, and residents relying on 149 water collection points around the city to collect a daily ration of 25 litres of water per person.[30][31] This would further affect Cape Town's economy, because of employees having "to take time off from work to wait in line for water".[32] Water supply would be maintained in the city's CBD, in informal settlements (where water is already collected from central locations) and essential services such as hospitals. At the time of the announcement, Day Zero was projected to take place on 22 April 2018, shortly afterwards revised forward to 12 April.[33][34][35] The Day Zero date is projected based on the fortnightly change in dam storage levels, assuming that this rate will continue unchanged, with no further rainfall or change in water demand.[36]
In February 2018, the Groenland Water Users' Association (a representative body for farmers in the Elgin and Grabouw agricultural areas around Cape Town) began releasing an additional 10 billion litres of water into the Steenbras Dam.[37]
Cape Town's largest reservoir, Theewaterskloof, was at 11% capacity in March 2018.
Residential water usage declined significantly under the 6B restrictions to a low of 511 million litres on March 12, the closest yet to the recommended level of 450 million litres per day. Agricultural use also declined significantly. As these reductions took effect and as water transferred from the Groenland Water Users' Association reached the city's water supply, Day Zero was moved back in stages from April to August,[38][39][40][41][36][3] and then postponed indefinitely.[42]
Severity of the drought[edit]
Research on long-term weather data done by the University of Cape Town found that the period from 2015-2017 has been the driest 3-year period since 1933, and 2017 was the driest year since 1933, and possibly earlier, since comparable data before 1933 was not available. It also found that a drought of this severity will statistically occur only once every 311 years.[23] Modelling by Aurecon found that the drought was approximately a 1 in 400 year event.[43]
“Once lush city parks and golf courses have withered, and public restrooms now urge visitors to flush only when absolutely necessary”.[32] Cafes began using plastic and paper cups and plates to reduce dishwashing loads. Analysts “estimate that the water crisis will cost some 300,000 jobs in agriculture and tens of thousands more in the service, hospitality and food sectors”. [32]
Impact[edit]
Poster issued by the Western Cape government calling for people to conserve water due to the water shortage in 2017.
In response to the water shortage, the agricultural sector reduced water consumption by 50 percent, contributing to the loss of 37,000 jobs in the sector nationally, and leading to an estimated 50,000 being pushed below the poverty line due to job losses and inflation due to increases in the price of food.[25] By February 2018 the agricultural sector had incurred R14 billion (US$1.17 billion) in losses due to the water shortage.[44]
In office buildings and many public places throughout Cape Town, water was removed from toilets to prevent flushing and aid in water conservation. Rainwater was directed to be added to the tank if the toilet needed flushing. However, residents have been directed not to flush the toilet if only urinating but use a disinfectant/scented spray afterwards. If defecating residents have been directed to use rainwater or greywater to flush. Hand sanitizer has also been provided in offices and public buildings to use instead of conventional handwashing to conserve water.
The city is urging residents to stock up on emergency drinking water. But the task is proving to be more difficult than residents thought. Stores are selling out of water the minute it is delivered and shopkeepers are uncertain when more will arrive. Residents can go to a natural spring to collect water but this means waiting in line for hours on end to fill their allotment. [32]
Public health[edit]
Residents of Cape Town have been restricted to only 50 litres of water per person per day, and are encouraged to flush toilets less often and only using non-potable water, and to reduce the length and frequency of showers. This has led public health professionals to raise concerns of diseases spread via faecal-oral contamination as a result of less hand-washing.
Inadequate sanitation is a leading cause of diarrhoeal diseases, which kill 2.2 million every year, with most deaths occurring among children younger than 5 years of age. With a population around 3.81 million and a population density of around 1530 per square kilometer, diseases like cholera and others could spread rapidly without proper sanitation, especially in impoverished neighborhoods in Cape Town. Without clean water the public health consequences continue as insects are attracted and reproduce in dirty waters, further spreading disease. The problem continues to snowball as standing water will bacteria and parasites start to grow.[45]
The Western Cape of South Africa has seen a “the second-highest incidence of listeriosis in South Africa”.[46] As a whole, South Africa has been victim to the largest outbreak of the disease on record. According to the Western Cape Health Department, 29 people have died of the disease since last year of 115 cases reported. Listeriosis can particularly threatens newborns as it can spread through lack of or inadequate hand-washing and failure to rinse vegetables, fruits, and other raw foods thoroughly. Officials warn that water-borne illnesses such as cholera, hepatitis A and typhoid fever “likely will become more prevalent” as residents begin storing water in contaminated containers.
Public health companies, research centres and health providers also worry about the impact the water crisis will have on health services. Some are thinking ahead to the impact of employees being unable to come into work because they are waiting in lines for water which are becoming longer and longer.[46]
Occupational health risks[edit]
Emergency shower and eyewash stations are an essential part of workplace safety for many laboratories and factories. A steady supply of water is necessary in the event of harmful chemical exposure. Many Occupational Health and Safety requirements suggest that all emergency showers be able to pump 75 litres per minute for a minimum of 15 minutes.[47] This would use approximately three weeks of water. If these wash stations are banned or limited, workers who handle highly corrosive chemicals would be vulnerable.
Fire risk increases as environment and infrastructure become increasingly dry. This is epically significant for large industrial sites and warehousing as fire on one site can spread more easily to other buildings in close proximity. Fire suppression system may also fail due to reduced water pressure in high-use areas.[48]
Vulnerable population[edit]
In homes and orphanages, children are one of the most vulnerable populations in Cape Town to suffer from health effects of water scarcity. The feeding, washing, and sterilization of items required to care for children is water intensive.[49] Furthermore, “If schools in the Western Cape have their taps turned off on Day Zero, 1.1 million children could be left stranded without water.”[50]
Industry[edit]
The agriculture industry is one of the largest consumers of water. The wine industry in and surrounding Cape Town is a major tourist draw and is a significant aspect of the economy, employing 300,000 workers. The wineries drew 1.5 million tourists in 2017 and at the same time used a third of the water.[51] Depending on the region, a vineyard needs between 10 and 24 inches of rain to survive. South Africa’s wineries have received on average half as much precipitation in the past year. The stress is being felt by industry where less water is causing smaller berries and therefore smaller yield. The industry also has a disproportionate profit with only about 1% return on investment despite producing some of the most popular wines in the world. The grape yield for 2018 could fall an estimated 20% from the 1.4 million tons produced in 2017, resulting in a 9% decrease in the volume of wine sold.[52]
The water crisis impacts organisations and industries that are not reliant on large volumes of water for their core operations as well such as corporate offices. The World Economic Forum's Global Risk Report 2015 [53] ranked the risk of a water crisis as the top risk in terms of impact. The cost of doing business in a drought affected area increases significantly. As workers move away or are evacuated from drought-affected areas the local economies suffer.
Hydrological poverty[edit]
Hydrologic poverty tends to trap their people as they cannot afford to purchase food or water necessary for their society to become more affluent. An analyst estimates that with the current water crisis 300,000 jobs could be lost in agriculture and tens of thousands more in the service, hospitality and food sectors [29]. In Cape Town it is illegal to sell water from wells or rivers but people can still profit from the transport and labor. One resident who had been stockpiling water was charging $350 for a barrel of water. This is further alienating the more impoverished neighborhoods and citizens of getting necessary clean water. Those who are using over the allocated daily water are being fined between $41-$248 [29]. Yet this impact is further cementing the gap because the fine is likely insignificant for the wealthy and can be crippling for less affluent residents. Increases in hydrological poverty, by the reduction of available water, could increase deaths in Cape Town by 25 to 33 percent. [54]
Political[edit]
Cape Town is governed by Mmusi Maimane, the leader of South Africa’s opposition party, the Democratic Alliance. Cape Town and Western Cape are the only province not run by the African National Congress (ANC) which has been in power since 1994. The tensions are high concerning many of the ANC would love to see the Democratic Alliance fail at the significant test ahead concerning the water crisis. Accusations of who has failed to act are being thrown by both sides [13] but it is clear both parties underestimated the magnitude of the problem. By taking control of the water crisis Maimane has pushed aside many constitutional structures set to separate party and state, complicating the situation and any reactions put in place. [55]
The Water Act of 1998 puts the national government as the “public trustee” of the nation’s water resources and must ensure that water is “protected, used, developed, conserved, managed and controlled in a sustainable and equitable manner, for the benefit of all persons”. It says: “The National Government, acting through the Minister, has the power to regulate the use, flow and control of all water in the Republic.”[56] With this both the local, provincial and national governments are responsible, yet with the unrest, working together has proved difficult.
Positives[edit]
This water crisis has increased research and investment in alternative water systems, which may ultimately help prevent other cities from falling into the same degree of water scarcity. As climate change continues and the population grows, moving into urban areas, other cities will also face severe drought and will need to assess alternative methods for obtaining water.[57]
The potential for a culture change in water usage is also a positive result of this crisis.
Solutions[edit]
The city of Cape Town is currently working on constructing four new desalination plants as well as building new water wells and an effluent recycler. By January 2018, these projects were half way through completion. In addition, the city has been working on educating the public on reducing water consumption. This has led to successful drop in water consumption by 50 percent from 2015 to early 2018.[58]
In addition, Cape Town is working on producing produce that accommodates the water availability of the region.[16]
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External links[edit]
Day Zero and Water-related FAQs
City of Cape Town Dam Levels Dashboard
City of Cape Town Day Zero Dashboard
City of Cape Town This Week's Dam Levels
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Multi-mode optical fiber
From Wikipedia, the free encyclopedia
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A stripped multi-mode fiber
Multi-mode optical fiber is a type of optical fiber mostly used for communication over short distances, such as within a building or on a campus. Typical multi-mode links have data rates of 10 Mbit/s to 10 Gbit/s over link lengths of up to 600 meters (2000 feet). Multi-mode fiber has a fairly large core diameter that enables multiple light modes to be propagated and limits the maximum length of a transmission link because of modal dispersion.
Contents
1 Applications
2 Comparison with single-mode fiber
3 Types
3.1 Comparison
4 Encircled flux
5 See also
6 References
7 External links
Applications[edit]
The equipment used for communications over multi-mode optical fiber is less expensive than that for single-mode optical fiber.[1] Typical transmission speed and distance limits are 100 Mbit/s for distances up to 2 km (100BASE-FX), 1 Gbit/s up to 1000 m, and 10 Gbit/s up to 550 m.[2]
Because of its high capacity and reliability, multi-mode optical fiber generally is used for backbone applications in buildings. An increasing number of users are taking the benefits of fiber closer to the user by running fiber to the desktop or to the zone. Standards-compliant architectures such as Centralized Cabling and fiber to the telecom enclosure offer users the ability to leverage the distance capabilities of fiber by centralizing electronics in telecommunications rooms, rather than having active electronics on each floor.
Comparison with single-mode fiber[edit]
The main difference between multi-mode and single-mode optical fiber is that the former has much larger core diameter, typically 50–100 micrometers; much larger than the wavelength of the light carried in it. Because of the large core and also the possibility of large numerical aperture, multi-mode fiber has higher "light-gathering" capacity than single-mode fiber. In practical terms, the larger core size simplifies connections and also allows the use of lower-cost electronics such as light-emitting diodes (LEDs) and vertical-cavity surface-emitting lasers (VCSELs) which operate at the 850 nm and 1300 nm wavelength (single-mode fibers used in telecommunications typically operate at 1310 or 1550 nm [3]). However, compared to single-mode fibers, the multi-mode fiber bandwidth–distance product limit is lower. Because multi-mode fiber has a larger core-size than single-mode fiber, it supports more than one propagation mode; hence it is limited by modal dispersion, while single mode is not.
The LED light sources sometimes used with multi-mode fiber produce a range of wavelengths and these each propagate at different speeds. This chromatic dispersion is another limit to the useful length for multi-mode fiber optic cable. In contrast, the lasers used to drive single-mode fibers produce coherent light of a single wavelength. Because of the modal dispersion, multi-mode fiber has higher pulse spreading rates than single mode fiber, limiting multi-mode fiber’s information transmission capacity.
Single-mode fibers are often used in high-precision scientific research because restricting the light to only one propagation mode allows it to be focused to an intense, diffraction-limited spot.
Jacket color is sometimes used to distinguish multi-mode cables from single-mode ones. The standard TIA-598C recommends, for non-military applications, the use of a yellow jacket for single-mode fiber, and orange or aqua for multi-mode fiber, depending on type.[4] Some vendors use violet to distinguish higher performance OM4 communications fiber from other types.[5]
Types[edit]
Multi-mode fibers are described by their core and cladding diameters. Thus, 62.5/125 µm multi-mode fiber has a core size of 62.5 micrometres (µm) and a cladding diameter of 125 µm. The transition between the core and cladding can be sharp, which is called a step-index profile, or a gradual transition, which is called a graded-index profile. The two types have different dispersion characteristics and thus different effective propagation distance.[6] Multi-mode fibers may be constructed with either graded or step-index profile.[7]
In addition, multi-mode fibers are described using a system of classification determined by the ISO 11801 standard — OM1, OM2, and OM3 — which is based on the modal bandwidth of the multi-mode fiber. OM4 (defined in TIA-492-AAAD) was finalized in August 2009,[8] and was published by the end of 2009 by the TIA.[9] OM4 cable will support 125m links at 40 and 100 Gbit/s. The letters "OM" stand for optical multi-mode.
For many years 62.5/125 µm (OM1) and conventional 50/125 µm multi-mode fiber (OM2) were widely deployed in premises applications. These fibers easily support applications ranging from Ethernet (10 Mbit/s) to gigabit Ethernet (1 Gbit/s) and, because of their relatively large core size, were ideal for use with LED transmitters. Newer deployments often use laser-optimized 50/125 µm multi-mode fiber (OM3). Fibers that meet this designation provide sufficient bandwidth to support 10 Gigabit Ethernet up to 300 meters. Optical fiber manufacturers have greatly refined their manufacturing process since that standard was issued and cables can be made that support 10 GbE up to 400 meters. Laser optimized multi-mode fiber (LOMMF) is designed for use with 850 nm VCSELs.
The migration to LOMMF/OM3 has occurred as users upgrade to higher speed networks. LEDs have a maximum modulation rate of 622 Mbit/s because they cannot be turned on/off fast enough to support higher bandwidth applications. VCSELs are capable of modulation over 10 Gbit/s and are used in many high speed networks.
Some 200 and 400 Gigabit Ethernet speeds use wavelength-division multiplexing (WDM) even for multi-mode fiber which isn't specified up to and including OM4. In 2017, OM5 has been standardized by TIA and ISO for WDM MMF, specifying not only a minimum modal bandwidth for 850 nm but a curve spanning from 850 to 953 nm.
Cables can sometimes be distinguished by jacket color: for 62.5/125 µm (OM1) and 50/125 µm (OM2), orange jackets are recommended, while aqua is recommended for 50/125 µm "laser optimized" OM3 and OM4 fiber.[4] Some fiber vendors use violet for "OM4+". OM5 is officially colored lime green.
VCSEL power profiles, along with variations in fiber uniformity, can cause modal dispersion which is measured by differential modal delay (DMD). Modal dispersion is caused by the different speeds of the individual modes in a light pulse. The net effect causes the light pulse to spread over distance, introducing intersymbol interference. The greater the length, the greater the modal dispersion. To combat modal dispersion, LOMMF is manufactured in a way that eliminates variations in the fiber which could affect the speed that a light pulse can travel. The refractive index profile is enhanced for VCSEL transmission and to prevent pulse spreading. As a result, the fibers maintain signal integrity over longer distances, thereby maximizing the bandwidth.
Comparison[edit]
Minimum reach of Ethernet variants over multi-mode fiber
Category
Minimum modal bandwidth
850 / 953 / 1300 nm[a]
Fast Ethernet 100BASE-FX
1 Gb (1000 Mb) Ethernet 1000BASE-SX
1 Gb (1000 Mb) Ethernet 1000BASE-LX
10 Gb Ethernet 10GBASE-SR
40 Gb Ethernet
40GBASE-SWDM4
40 Gb Ethernet 40GBASE-SR4
100 Gb Ethernet 100GBASE-SR10
FDDI (62.5/125) 160 / – / 500 MHz·km 2000 m[10] 220 m[11] 550 m[12] (mode-conditioning patch cord required)[13][14] 26 m[15] Not Supported Not supported Not supported
OM1 (62.5/125) 200 / – / 500 MHz·km 275 m[11] 33 m[10] Not Supported Not supported Not supported
OM2 (50/125) 500 / – / 500 MHz·km 550 m[2] 82 m[2] Not Supported Not supported Not supported
OM3 (50/125) *Laser Optimized* 1500 / – / 500 MHz·km 550 m (no mode-conditioning patch cord should be used)[16] 300 m[10] 240m[17]
Duplex LC
100 m[2]
(330 m QSFP+ eSR4[18])
100 m[2]
OM4 (50/125) *Laser Optimized* 3500 / – / 500 MHz·km 400 m[19] 350m[20]
Duplex LC
150 m[2]
(550 m QSFP+ eSR4[18])
150 m[2]
OM5 (50/125) "Wideband multi-mode" for short-wave WDM[21] 3500 / 1850 / 500 MHz·km
Jump up ^ OFL Over-Filled Launch for 850/953 nm / EMB Effective Modal Bandwidth for 1310 nm
Encircled flux[edit]
The IEC 61280-4-1 (now TIA-526-14-B) standard defines encircled flux which specifies test light injection sizes (for various fiber diameters) to make sure the fiber core is not over-filled or under-filled to allow more reproducible (and less variable) link-loss measurements.[22]
See also[edit]
Fiber-optic communication
Graded-index fiber
ISO/IEC 11801
IEEE 802.3
References[edit]
Jump up ^ Telecommunications Industry Association. "Multimode Fiber for Enterprise Networks". Retrieved Jun 4, 2008.
^ Jump up to: a b c d e f g Furukawa Electric North America. "OM4 - The next generation of multimode fiber" (pdf). Retrieved May 16, 2012.
Jump up ^ ARC Electronics (Oct 1, 2007). "Fiber Optic Cable Tutorial". Retrieved March 4, 2015.
^ Jump up to: a b "Fiber optic cable color codes". Tech Topics. The Fiber Optic Association. Retrieved Sep 17, 2009.
Jump up ^ Crawford, Dwayne (Sep 11, 2013). "Who is Erika Violet and what is she doing in my data center?". Tech Topics. Belden. Retrieved Feb 12, 2014.
Jump up ^ British FibreOptic Industry Association. "Optical Fibers Explained" (PDF). Retrieved Apr 9, 2011.
Jump up ^ "Fiber Optics Overview". Retrieved 2012-11-23.
Jump up ^ "Meeting Report #14" (PDF). Telecommunications Industry Association.
Jump up ^ Kish, Paul (2010-01-01). "Next generation fiber arrives". # Cabling Networking Systems. Business Information Group.
^ Jump up to: a b c Hewlett-Packard Development Company, L.P. (2007). "100BASE-FX Technical Brief" (PDF). Archived from the original (pdf) on 2012-10-09. Retrieved Nov 20, 2012.
^ Jump up to: a b IEEE 802.3-2012 Clause 38.3
Jump up ^ IEEE 802.3 38.4 PMD to MDI optical specifications for 1000BASE-LX
Jump up ^ Cisco Systems, Inc (2009). "Cisco Mode-Conditioning Patch Cord Installation Note". Retrieved Feb 20, 2015.
Jump up ^ As with all multi-mode fiber connections, the MMF segment of the patch cord should match the type of fiber in the cable plant (Clause 38.11.4).
Jump up ^ "Cisco 10GBASE X2 Modules Data Sheet". Cisco. Retrieved June 23, 2015.
Jump up ^ "A mode-conditioning patch cord should never be used for applications over OM3 and more recent fiber types". Cisco. Retrieved 2018-03-07.
Jump up ^ "40GE SWDM4 QSFP+ Optical Transceiver | Finisar Corporation". www.finisar.com. Retrieved 2018-02-06.
^ Jump up to: a b "40G Extended Reach with Corning Cable Systems OM3/OM4 Connectivity with the Avago 40G QSFP+ eSR4 Transceiver" (pdf). Corning. 2013. Retrieved 14 August 2013.
Jump up ^ "IEEE 802.3". Retrieved 31 October 2014.
Jump up ^ "40GE SWDM4 QSFP+ Optical Transceiver | Finisar Corporation". www.finisar.com. Retrieved 2018-02-06.
Jump up ^ "TIA Updates Data Center Cabling Standard to Keep Pace with Rapid Technology Advancements". TIA. 2017-08-09. Retrieved 2018-08-27.
Jump up ^ Goldstein, Seymour. "Encircled flux improves test equipment loss measurements". Cabling Installation & Maintenance. Retrieved 1 June 2017.
Force, Inc. (2005-04-14). "Types of Optical Fiber". Archived from the original on October 12, 2007. Retrieved Apr 17, 2008.
Hayes, Jim; Karen Hayes (Mar 22, 2008). "Lennie Lightwave's Guide to Fiber Optics". Retrieved Jun 4, 2008.
International Engineering Consortium. "Fiber Optic Technology". Retrieved Jun 4, 2008.
Telecommunications Industry Association. "Multimode Fiber for Enterprise Networks". Retrieved Jun 4, 2008.
Telecommunications Industry Association (Sep 2008). "Choosing the right multimode fiber for data communications" (pdf). Retrieved Nov 17, 2008.
Hewlett-Packard Development Company, L.P. (2007). "100BASE-FX Technical Brief" (PDF). Archived from the original (pdf) on 2012-10-09. Retrieved Nov 20, 2012.
External links[edit]
Optics: Single mode fiber | MIT Video Demonstrations in Lasers and Optics
Optics: Multi-mode fiber | MIT Video Demonstrations in Lasers and Optics
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This page was last edited on 27 August 2018, at 19:03 (UTC).
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