Remote Radio Unit | RRU Functions | Details

Remote Radio Unit | RRU Functions | Details 

This whole blog article is being shifted to RRU-Remote Radio Unit Functions. Dear All, we will now post new article in this website named www.telecomkhabar.com . Please use this website and suggest me so I can give you a good concept and knowledge. 
Thank you for supporting me for last 4 years.

Topics Covering:

a) RRU Definition and Overview 

b) RRU Functions

c) RRU Hardware Description & many more

Radio Remote Unit(RRU) is the distributed and integrated frequency unit that connects to an operators network with the User Equipment's (UE's) like Cell Phone and mobile devices.

Fig: RRU mounting in tower

The logical term "distributed and integrated"  is because traditionally the radio architecture for cellular system is based on a single-standalone system(Base Stations) usually installed indoor but now, the cellular architecture is divided.
So now the BTS(Base Transceiver Station) is the integration of various radio unit like BBU and RRU. Despite installing only in indoor , radio units are now installed in the tower below the Antenna.

The RRU is connected to the base station via the fiber optic link which is bi-directional link. The optical interface link is also known as CPRI (Common Public Radio Interface). CPRI is a interface protocol developed by combination of major telecom equipment's manufacturing company.

The RRU helps to reduce the coaxial feed line losses, increase system efficiency  and provide high level of flexibility in cellular site construction. Undoubtedly, this helps in upgrading to new equipment's and devices more easily.

RRU Functions: 

I have jotted down the RRU functions here.

1) Acts as a transceiver: transmit and receive the user signals to the base station and vice-versa.

2) Provides back to back support and connectivity between user equipment's like power, delay,etc.

3) Control and process the EM signals received from the Antenna via Jumper(Hollow Guide).

4) Provide interface between two physical  link: Optical and EM(Electromagnetic).

5) Provide Controlling support of the Auxiliary equipment's like  RCU (Remote Control Unit) for electrical tilt adjustment generally known as RET(Remote Electrical Tilt).

6) Generate and sends the different signals like   VSWR, RET, ACT,etc. 


RRU Hardware Description:

Fig: Port Showing for connection in Huawei RRU

RRU consist of different ports for different purposes. I have summarize the ports that are common among various companies like Huawei, ZTE, Ericsson, Alcatel-Lucent, Orange,etc.

1) CPRI Port:  There is 2 port generally named as CPRI0 and CPRI1. However there may be 1's in some model. The name at suffix may vary. Its function is to connect to BBU.

2) RF Port: We say it as a Jumper port. The number of jumper port may vary with model and company's architecture. At least there is 2 jumper port, one of which is for Tx and another for Tx/Rx. The RF port is connected to the Antenna via Jumper Cable. 

3) RET Port: There is at least one RET port for connection to RCU. The connector is mostly DB9 in Huawei and may vary with other company's. RCU is connected to the Antenna. RET cable connects the RCU and RRU.

4) Power Supply Port: There is one port for powering the RRU. Mostly blue and black. Blue is for negative (-) and black is for zero(0). Generally all RRU operates in -48V.

5) Ground Port: There is two OT port for the grounding. The ground cable: mostly copper wire, one end is connected to RRU and another end into Bus Bar near by RRU. Thus it provides the surge and high voltage protection of RRU and thus keeping safe from natural weather and climates. 

White Space Radio|Next Generation Communication

White Space Radio|Next Generation Communication 

"Everything you need to know about White Space"

"White  Space" refers to the unused broadcasting frequencies. According to Center for white space communicaton, white space is termed as-"parts of the radio spectrum that are not utilized all of the time or in all geographical locations". 

Since,there are many frequencies which are divided into different spectrum by international and national authority for different purposes. So among those frequency also, there is frequency gap maintained to mitigate the interference among the divided frequency- which is called guard band or guard frequency.

Beside, guard frequency; the switch-over of analog TV to Digital TV have leftover unused many frequency. Since, digital transmission broadcast many signals by compressing in parallel which on conclusion left unused frequency. So such frequency is termed as white space. And the technology is termed as white space technology.

To use such white space frequency, special devices known as White space devices(WSD) have to be used. The WSD have to be present to both sides. The WSD are designed to detect the presence of existing but unused areas of frequency and utilize these unused frequency for internet connectivity or other broadcasting purpose. Currently the WSD are manufactured by Adaptrum, Carlson wireless, Redline communications,etc.

Tech company like Microsoft, Google, Nokia, BBC too have been keen motivated in upgrading of White space radio. They have been doing research in different university and lab of different country. United states, United kingdom, Canada have been doing trail in various states. 
In July 2013, West Virginia University became the first university in the United States to use vacant broadcast TV channels to provide the campus and nearby areas with wireless broadband internet service. 

There is much more potential in developing countries and in rural areas. Developing countries yet have not access to internet connectivity to school and houses. 
The cell tower once established can serve upto 10 km in distance so this helps in point to point connectivity for long distance. 

Kenya, South Africa, Namibia are the countries where there have been use of white space to deliver the internet connectivity in rural areas and schools. Soon other developing countries of Africa and Asia will be adopting this White Space radio. India on making "Digital India" will make better utilize of this radio.

The History of VoIP, which you must know

VoIP History 

VoIP is the fastest growing technology. Where did all this technology came from and how it is developed? Lets go back into time and find out all this things. But before this, If you are unknown about the VoIP and its working process, simply click the highlighted text.

  

Pic: Analog Switching system for PSTN during 1960

In 1973, Motorola made the first phone call using cellular technology to Bell Labs. Now after the cellular technology, VOIP story actually started in the summer of 1974, when the ARPANET(Advanced Research Projects Agency)  sent a 16 kb/s real time voice sample between computers based at the information Sciences Institute and the Lincoln lab, United States. 

In the preceding year, there was no much more influence and growth of broadband Internet, So this has been the major influence in the VoIP. But in back 1995, the Vocaltec, software company achieved the initial success with Internet phone and delivering VoIP software application. This have been the breakthrough in the growing of voice over IP.  

In 1998, in USA alone , 1% of all calls was done through VoIP. By 2000, this percent have been increased to 3%.  

In the later years, with the surplus increase in broadband connectivity , VoIP market have been rampant increase.  In 2004, VoIP telephony had begun with the introduction of VoIP calling plans, which is similar to telephone company and using PSTN. Very low rate, offer and discount have heavily increase the market of VoIP. But with increasing VoIP services, many telecom operators have been been faced  loss in millions of dollars monthly due to call bypass and terminating the call without the use of operator gateway. So some country, still have set the VoIP illegal.

What is VoIP and How VoIP works

In this Post, we will discuss in-depth knowledge regarding VoIP and will cover  major topic which includes:

1. What is VoIP and how it works?

2. VoIP history

3. What is VoIP phone system?

4. VoIP business 

5. How VoIP is challenging the telecom operators around the               world?

6. Technology used in VoIP service 

7. Many more including how to set up VoIP by yourself

What is VoIP ?

VoIP stands for Voice over Internet Protocol. It is used to send our voice signals via internet communication method instead of local telephone company. VoIP technology involves sending of analog signals(our talks) by converting into digital discrete signals and transmit the discrete signals in the form of packet data via internet. One of the widely used VoIP example is Skype, Viber, etc. 

How it works different from mobile phone and PSTN ?

In PSTN, our voice is transmitted over copper wire as an analog signals between frequency 0-4KHz. In modern cell phone, the cell phone converts our voice into an electrical signals, which is then transmitted as radio waves with using different modulation technique to secure our privacy. 

But in case of VoIP, the voice signals is converted into packet data, i.e  the voice signals are break down and is changed into the packet data. For this various codec method is used.The packet size is defines by the voice over ip packet structure. For example , if size is 4Kb then we can roughly conclude that our voice signals is converted into 4Kb packet size and send over internet time and again. This process is very fast, which is just a work of fraction of second and we cannot even notice it. 
Now in the other end, the packet data is now decrypted. And the packet data is converted to the standard audio signal. Thus communication is established.

Don't miss the history of VoIP.

Battery Bank and It's Importance in Telecom

Dear Members, we are now completely upgrading this blog to our own website named telecomkhabar. we are now discontinuing this blog and new content will be available in https://www.telecomkhabar.com. 
This article is now being moved to this link named Battery Bank importance in telecom. 



After successful completion of reading this post, you will learn!!!

a) Why 2V battery is used in telecom industry??
b) Do site gets down, when battery gets damaged??
c) Details of outdoor sites and indoor sites
d) Choice for no of batteries used in site??

Pic(a): Single BB of 12V each with 12 batteries

Collection and arrangement of Battery is termed as Battery Bank or shortly BB. Battery Bank consist of few minimum 4 batteries to maximum no. of batteries as required. Battery Bank in telecom industry is most common for power backup which may need during AC line faulty. Battery bank is used to store current of Photo voltaic energy, AC rectified to DC power or Diesel Generator power.

Batteries are kept in the cabinet or in the dorm as per the site location and feasibility. Cabinet is used where the site is outdoor. Outdoor site is where BBU, DCDU, battery bank,and everything equipment is kept in a closed box sealed such that no water enters into it under the open sky. Pic(a) is clear example of outdoor site where battery bank is kept in the cabinet for protection from direct sunlight, water and direct air.

For indoor site, where every equipment is kept inside the shelter or in the room, batteries are kept in the dorm. This saves the cost of the cabinet. The Pic(b) below shows the example of indoor site and battery placement in the dorm. 

Pic(b): Two BB with each 2V, 24 batteries in each bank

In the Picture above, Pic(a) consists of 16 batteries and Pic(c) consist of 48 batteries. The choice for the number of batteries on the desired site depends on the following two important reasons:

1) For the Hub site(multiple links from same site is done): more batteries with more power is installed for providing microwave link until last minute because multiple links are operated by the same site.

2) For very busy traffic areas:places where users traffic is high and need to provide continuing services, more batteries for longer power back is kept.

Most of the telecom equipment's are made to run in negative voltage because  for the protection for high voltage lightning. So the batteries are arranged to give maximum of -48V.

Don't get confused, positive terminal of battery is grounded and negative is used to give up -48v.

Batteries are arranged in series to sum up for 48V and then more batteries are connected in parallel. Parallel connections provide long lasting current for the same output. That is why more batteries are kept and connected in parallel in HUB and High Traffic sites.

Telecommunication field is crucial as communication is very important. If there is power failure then the site gets down and whole communication of the site as well the link of other site is also down. Suppose if single 2v battery get damaged, then we can replace instantly that battery but still there is -46 voltage and sites don't get down because the telecom equipment's run upto -44v. If we used battery of more voltage then if by change battery gets damaged or need to replace then the sum of voltage will gets down below 44v and the sites gets down. Due to this reasons, at least 2 parallel connections and 2v battery is mostly used.

Most common battery used are of Shoto, Agission, Northstar,   Exide etc.

If you find this post useful, please give me thumps up by like and share or if something is missing or if you want more concept, ideas and details of other telecom equipment's please leave comment in the comment section below. I will  include those topics in my coming post. Thank you

BBU-Baseband Unit- in Telecom

BBU-Base Band Unit

This whole blog article is being shifted to BBU Base Band Unit in Telecom . Dear All, we will now post new article in this website named www.telecomkhabar.com . Please use this website and suggest me so I can give you a good concept and knowledge. 

Thank you for supporting me for last 4 years. 

Base Band refers to original signal or un-modulated signals ie signals which occupies the lowest range of frequency spectrum. BBU processes the signal of original frequency before it is modulated. 

In Base band, Frequency band is not shifted to some other frequency band by means of modulating.

BBU have DSP(DIgital signal processor) that process the conversion of signals conversions between analog and digital signals. It is also known as heart of communication because it serves for communication link between two end users. 

BBU along with RRU (Radio Remote Unit) formed as a BTS. RRU process the incoming and outgoing radio signals. RRU sends the signals and receive signals (EM waves) from Antenna through hollow guided Jumper .BTS is Base Transceiver station. BBU is connected with RRU through CPRI-Common Public Radio Interface fiber cable for making BTS. 

Fig: Typical  BBU of Huawei 3900 Series 

Functions of BBU-

1) Provides common public radio interface (CPRI) ports or optical links for communication with RRUs and processes uplink and downlink baseband signals.

2) Provides S1 ports for communication between an E-UTRAN NodeB (eNodeB) and an
MME/S-GW, and X2 ports for communication between eNodeBs.


3) Provides clock ports for clock synchronization, alarm monitoring ports for environment monitoring, and a Universal Serial Bus (USB) port for commissioning using a USB flash drive.

4) Manages the eNodeB through operation and maintenance (OM) and signaling message processing.

As in above figure, commonly BBU consists of FAN, LBBP, UMPT, UPEU and other slots where necessary cards is inserted for needed operation. Brief description of each above components is given below:

a) FAN: The FAN dissipates heat from the BBU3900. It monitors the inlet temperature, controls the rotation speed of the fans, and reports the status of the fans to the LMPT or UMPT in the BBU3900.

b) LBBP: LBBP stands for LTE Base Band Processing Unit. Huawei 3900 series have 3 different LBBP, LBBPa, LBBPb and LBBPc. But in Huawei BBU 3910, LBBP is termed as UBBP. LBBP and UBBP difference is that LBBP is for LTE or 4G communication while UBBP is for 2g and 3g communication. UBBP also have type 3 and type 2 cards, UBBP2 and UBBP3. These both LBBP and UBBP functions is to:

    1) Provides CPRI ports for communication with radio frequency          (RF) modules.
    2) Processes uplink and downlink baseband signals.

 

Fig: UBBP2 and UBBP3 cards and CPRI cable shown in Huawei BBU 3910

c) UMPT: UMPT stands for Universal Main Processing and Transmission Unit. Its functions are:
 1) Performs OM functions, including configuration management, equipment management, performance monitoring, signaling processing, and active/standby switchover.
 2)Provides clock reference,transmission ports,and the maintenance link connecting to the OMC.The OMC can be the LMT or M2000 client.

d) UPEU: UPEU stands for Universal Power and Environment interface unit. Its functions are:
 1) Converts power of -48v input into +12V with 300 watt and 650 watt power needed for BBU operation and Processing.
 2) It takes EMUB signals through RS485 serial communication and converts into Boolean signals. Thus acts as interface unit for BBU and EMUB unit. EMUB is Environment Monitoring unit for sensors alarm.

BBU consists of GPS sensors or device which track the BBU installed location and if BBU is stolen or theft the GPS coordinate is traced and send back to telecom operator control room.

There are many BBU models manufactured by various telecom operators. The top 5 telecom equipment manufacturer are Ericsson, Alcatel-Lucent, Huawei Technologies, Cisco Systems and ZTE Corporation. These vendors have their own type type BBU model though the basic knowledge is same. The different is that of their power efficiency & processing and working speed.


If you find this post useful, please like and share or if something is missing or if you want more concept, ideas and details of other telecom equipment's please leave comment in the comment section below. I will try to include those topics in my coming post.

4G in Nepal!!! Is really a 4G or LTE??? It’s Scope and Hurdles…

4G in Nepal!!! Is really a 4G or LTE??? It’s Scope and Hurdles…

Finally,Nepal government, Ministry of Information and Communication have decided to adopt a technology neutral policy to allow operators to lunch 4G using the 1800-MHz. So now operators can lunch the 4G service to its customers.

Before few weeks, Nepal Telecommunication Authority(NTA) : a government head body that monitors, governs and regulates the telecom operators  in Nepal: announces  that  it is preparing for the frequency spectrum , frequency distribution and cost analysis &  also announces for submission of proposal  for 4G operation to the operators. This declaration has opened the door for the telecom Operators to lunch the 4G LTE service in Nepal. This announcement has been taken a good response from the public people as well.

Is it really a 4G or LTE???

4G is the 4^th generation mobile data service with its high speed download and upload of packet data.

LTE is Long Term Evolution as the next generation data service aimed to fulfill the demand of 3^rd generation data scarcity. LTE have been constantly developed and improved. So LTE-A (A-advanced) is the next generation LTE service. LTE can be upgraded with the utilization on ongoing GSM and UMTS carrier.

Many of us and even operators have been consciously used the term LTE and 4G interchangeably. Technically they are different.  4G define the D/L (Downlink) data rates of 100Mb/s during high mobility i.e during travelling with high speed on bus, trains & 1 Gb/s during stationary. Now let’s examine the speed on those countries where 4G is deployed. The above speed has not been achieved yet. Cellphone power, cell phone antenna, MIMO (Multiple Input Multiple Output), carrier aggregation, etc. are the several technical challenges behind this.

However, on contrary LTE defines the theoretical speed of 100Mb/s as D/L. The practical speed has been varied among operators. It is based on the GSM/EDGE and UMTS/HSPA network technologies, increasing the capacity and speed using a different radio interface together with core network improvements. LTE have been in operation in 16 countries as of 2015 and is being deployed by 140 operators in 56 countries.

The two major operators NT and Ncell on their statement expressed, they are willing to lunch the 4G LTE service. 

NT plans to provide within all 75 districts of Nepal 4G service by 2017/18 but it hasn’t been able to keep up its place to meet its targets. Since, NT still hasn’t provided 3G service to all over Nepal. Its in the expansion process. So to meets its target is yet dubious and challenging itself.

Ncell now owned by Axiata Group, a competitor of NT has been  focused on quality services with adaption of 3G. Focusing on major cities, it has already provided 3G services. Ncell have shown keen interest for adoption of 4G-LTE  before few months. At that time even NTA had not been prepared and planned for frequency distribution .

5 Essential Tools that Every Telecom Engineer should have on their bag

Being a Telecom Engineer and executing the task is itself a difficult job. Telecom Engineer should always be smart, diligent, sharp, active and problem solving beyond every new faces of problems. 

We should troubleshoot problems no matter what the problems is. 

I have listed top five tools that will help every Site or Telecom Engineer to solve majority of problems. 

1) RJ45 CAT5 Network LAN Crimper Tools, LAN Cable, LAN Tester and CAT-5 connectors:

Lan Crimper along with few(5-10m) LAN cable is very necessary. Few pieces of around 20 connectors will add a life in our task. We can now easily make new LAN cable and use it where we need. 

 We can now even check the existing lan cable faulty with our LAN tester and we can easily replace the existing LAN cable. We can use also use the same LAN cable for interfacing and commissioning new devices as required. So it has been a essential tools that we should not forget under any circumstance.

2) Screw Driver Set: Screw driver is general and multipurpose tools that every technicians and engineer should carry along with them. It accomplished different works.

 It can be used to open the different cards of BBU, RRU and even different Transmission Equipment's like CX, OSN, CISCO, Alcatel,etc. If you find it more bulgy and heavy, never miss the two set tools +/- in big and small size in your bag.

3. Tie Cutter with few Black and White cable tie: To clamp the cable in proper order, we need cable tie. Routing with proper tie makes the site and cables good looking.

Tools is simple but has great use while routing, fixing new and old cables in proper places. Generally Black tie is used at outdoor and white tie is used at indoor. 

4. Multimeter: No matter what new devices and equipment, whom with we play: 

Multimeter has its own remark in the Telecom Engineering. Most common, most versatile and most needed devices that every telecom engineer must posses. Power failure, short circuit, continuity test, current measurement, voltage measurement, resistance measurement,etc are done by multimeter. It has been a major tool for troubleshooting telecom equipment and devices.

5. Labels: Labels are need to show where the cable has been gone and where it ends. In BTS we can see large number of cables routed here and there. If we don't label the cables properly we may incorrectly plugged in and out of other cables and may risk in "site down". " Imagine- If it was a Hub site, then the whole city or region may go silent". The result is worse and even scary. So for proper labeling at both end, we must have either printed or hand written label. So we should always carry blank label in our bag so we can used it for temporary in case needed. 

We can see the labeling done at Fiber Cable , and thus we can easily know where it has been routed. 

I have listed major 5 tools above. Let me know other tools in the comment section below which I have not listed.

China builds fastest supercomputer with it's own advanced "CHIP"

China have been dominating world on Supercomputer battle for few years. 

Now it have enormously become the world top supercomputer holder with its own processor after US restricted in using Intel  chips,as published on June by top500.org
It is the first system to exceed 100 petaflops. A petaflop equals one thousand trillion(one quadrillion) sustained floating-point operations per second. 

The fasted supercomputer was named as  "Sunway Taihulight". The "Sunway Taihulight" has a peak processing speed of 125 petaflops per second while averaging at 93.It's calculation capacity in one minute equals 32 years of calculation by the world 7 billion people using calculators.

Internet Radio

Internet Radio 

AM and FM broadcasting is to all broadcasting type whereas internal radio can be one to one(uni-casting) or one to many(multicasting).

Internet radio is an audio broadcasting service transmitted via internet. Broadcasting on internet is usually referred as webcasting. Internet radio involves streaming medium that presents listeners with continuous stream of audio, using lossy audio codec. Streaming format includes MPs, Window Media Audio, Real audio.

Program produced by studio is feed to an encoder which compressors the audio and encodes  for distribution over internet. Hardware or software encoding can be used.

The compressed stream is feed to server which copies the stream for each of the client. The service provider allocates certain bandwidth for the feed.

The data stream is transmitted over public internet where each data is broken into packets and distributed using internet protocol.

DTH TV(Direct to Home)

DTH TV(Direct to Home) 

DTH is used to refer Satellite Television broadcast intended for home reception specific band(11.7-12.2 GHz).

Most of the developed television company set their broadcast through Direct Broadcast Satellite(DBS). The provider selects program and broadcast them to subscriber as a set of language. It has high stereo and picture quality.

Pic: DTH-TV SET 

The broadcast center converts all the programming into high quality uncompressed digital stream. The provider needs to encrypt in order to keep people from accessing it for free.

All the signal is encrypted and compressed, broadcasting center directly beams it up to one of its satellite. The satellite amplifies the signal and beams it back to earth where viewer can pack it up. 

Online Colleges: Learn anywhere, Learn Anytime

Online Colleges and Education: Learn Anywhere, Learn Anytime

There are around 23 thousand universities around the world. Every year more than 200 million students enrolled in colleges and universities around the world. USA alone, in fall 2015 expects to enroll 20.2 million students in Colleges and University Education among its around 4200 university and colleges. 

In USA alone, yearly 2.2 million people have their degree through online education and this number is increasingly rapidly. The significant increase towards having online degree may have been effected by the low cost, time saving, and flexibility for access to education.

Worldwide more than thousand of university offer online courses. From top ranking university like Harvard and MIT, to community colleges are offering the distant learning education system. Many of among those universities also provide free online courses and charge few dollars for exam and certification card. 

The rampant increase in online degree education have saved time of students and thus students can utilize the time for other work. They can engage in part time jobs along with getting university degree. Though some of the courses are of very short duration although they are very magic-effective. As a result, short term training courses have been very effective like professional course in programming, learning grammar and punctuation,skeptic drawing,etc. 

I have listed top 10 online colleges and universities that have been in top position according to "thebestschools.org". They have been imparting online education to its students through Radio or Television, World Wide Web, Mail, Podcast, Online Video, Video Conferencing,etc.

1. Penn State World Campus

2. University of Florida: Distance Learning

3. Umores online

4. Boston University

5. Northeastern University

6. Indiana University,IU Online

7. Arizona State University, ASU Online

8. Florida State University, Office of Distant Learning 

9. Drexel University, Drexel Online

10. Oregon State University, OSU Campus

These universities offer various courses on Undergraduate, Graduate, Postgraduate and Doctorate Level. Some of the courses they offer are:

1) E-MBA

2) Programming like C,C++,Java, Python

3) Image Processing using Matlab

4) Big Data

5) Project Management

6) Machine Learning

7) Medical Neuroscience

8) Data Science

9) Language Learning like Spanish, German, Japanese,etc

10) Excel, MS-Word, PowerPoint,etc and many more

Also there are many more free online courses which have been providing by non-profit organization like edX which contains courses of MIT, Harvard, Cornell University,Australian National University,and many more. 

CPRI Cable Function and Details in Telecom

After successful completion reading of this post you will know!!!

Dear All, we are now having our own site named telecomkhabar. This article is now moved into the new link as CPRI functions in telecom. Please follow the new site for new updates as this blog is now discontinued. 
Thank you for supporting for 4 years. 

a) What is CPRI cable?

b) Use of CPRI cable in telecom

c) Interconnection of CPRI cable in BBU and RRU

d) CPRI connector details or Fiber connector types

CPRI stands for Common Public Radio Interface.

CPRI is the world standard interface defined for Radio Equipment Controllers(REC). REC are basically Base Band Unit(BBU), Remote Radio Unit(RRU) in telecom industry. CPRI standard is followed by top leading telecom equipment manufacturer like Huawei,, Ericsson,Nokia,NEC,etc.

CPRI Functions :

CPRI is optical fiber that carry signals whether it is control or message. Control signals are the controlling signal that carry information of the status of the equipment installed in the BTS and other various traffic related control signals. Message signals is the information related to user communication. 

CPRI supports multi mode communication and doesn't support single mode communication. In optical fiber, single mode communication is that where single light is transmitted between two radio equipment for communication and data transfers whereas multi-mode supports more than one light to be transmitted through the same single optical fiber link at a time. Thus multi-mode is used for communication in very short distance whereas single mode is used for long distance communication because of low loss in single mode fiber.

Pic: SFP for Optical Fiber(CPRI) connection 

Below is the chart of the Optical fiber connector types: (source:Alibaba)

Among most of the connector types, LC-Duplex is very common in Telecom Industry for connecting BBU and RRU. 

LC-(Simplex and Duplex) is a push on,pull-off, multimode or singlemode fiber type of connector containing a standard RJ 45 telephone plug housing with a ceramic ferrule in a simplex or duplex plastic housing; SFF(Small Form Factor)and SFP(Small Form Pluggable) designs are suitable for high density interconnection and also useful for instrumentation and test equipment interconnections. It have insertion loss of  0.1 to 0.5 dB. 

If you find this post useful, please give me thumps up by like and share or if something is missing or if you want more concept, ideas and details of other telecom equipment's please leave comment in the comment section below. I will  include those topics in my coming post. Thank you