What is a Bidirectional Optical WDM BIDI Transceiver?

Commonly, optical networks rely on transceivers that utilize one optical fiber to transmit data and another optical fiber to receive data to and from the networking devices. Generally, this kind of data transmission raises the costs of the network deployment, however with use of the bidirectional optical WDM BIDI transceiver, and its capability to send and receive data over one optical fiber, we can create a much more cost-effective optical networks.

The Bidirectional Optical Transceiver or BIDI, is a type of an optical transceiver which uses the Wavelength Division Multiplexing technology or widely known as WDM technology. The BIDI transceiver manages to do this with the help of the integral bidirectional coupler which transmits and receives signals.

The main difference that differentiates BIDI transceivers from standard, two fiber transceivers, is the possibility of the BIDI transceiver to send and receive optical light data through a single fiber. This is easily illustrated in the pictures below which offer a side to side comparison between these two types of transceivers. The other key difference between the standard and BIDI transceiver is the introduction of Wavelength Division Multiplexing technology incorporated into BIDI transceivers. This technology separates the data sent and received over the same fiber based on the wavelengths of the light. However, to work at maximum level, the BIDI transceiver must be deployed in matched pairs and tuned to match the expected wavelength of the transmitter and receiver they are transmitting and receiving data from and to. To put things in perspective, if one transceiver is transmitting wavelengths of 1310 nm, the other side must have a receiving wavelength of 1310 nm and vice-versa.

Figure 1:
BO55J27640D- BlueOptics© Bidi SFP+ 10GBASE-BX-U, TX1270nm/RX1330nm, 40KM, Optical Fiber Transceiver, DDM/DOM

Figure 2:
BO35H13610D- BlueOptics© SFP+ 2/4/8G FC LW, 1310nm, 10KM, Optical Fiber Transceiver, DDM/DOM

The common types of BIDI transceivers used in today’s networks are:

  • Bidirectional X2 Optical Transceiver - designed for 10GB serial data communications. This transceiver is made of two sections with the transmitter part using a multiple quantum 1330/1270 nm Distributed Feedback Laser. The receiving part of the transceiver uses an integrated detector with preamplifier for 1270/1330 nm. This optical transceiver is mainly used in Ethernet solutions.
  • Bidirectional SFP Optical Transceiver - this transceiver is most commonly deployed in high speed duplex data links over a single optical fiber. The most common optical wavelengths for this transceiver is 1310/1490 nm, 1490/1550 nm, 1310/1550 nm and 1510/1570 nm. This type of transceivers is used in optical communication for optical telecommunications and optical data bidirectional applications.
  • Bidirectional SFP+ Optical Transceiver - This type of transceiver is a more advanced version of the BIDI SFP transceiver. It is designed for 10 GB deployment and distances up to 20 kilometers.
  • Bidirectional QSFP Optical Transceiver- This transceiver most commonly has two 20 GB/s channels with each transmitted and received at the same time over a single Multi-mode strand (OM3 or OM4).

The obvious advantage of using Bidirectional transceivers is simple. Reducing the fiber optic cable infrastructure, reducing the number of patch cords and panels and thus reducing the overall cost of the Network Solution. Even though Bidirectional Optical Transceivers cost more to purchase them, deploying them will eventually result in cutting down half of the amount of fiber per distance needed for a certain project.

Today the Bidirectional Optical Transceivers are mainly used in FTTH/FTTB active Ethernet point-to-point connections. These connections consist of a central office, or premises equipment (PE), connecting to the CPE or widely known as Customer Premises Equipment. Active Ethernet solution uses the point-to-point technology in which each customer is connected to the PE on a dedicated fiber. In this case the use of BIDI transceivers is essential because it provides a bidirectional communication over a single fiber by using the WDM technology making the connection simpler to deploy, troubleshoot and configure.   

What is 10GBase-LRM Transceiver and why do I need it?

10G Ethernet (10GE,10GbE or 10GigE)

  • Is a set of technologies that permits transmissions of Ethernet frames at a rate of 10 gigabits per second. 10 Gigabit Ethernet defines only full duplex point-to-point links which are generally connected by network switches.10GbE can use either copper or fiber cabling.The 10 Gigabit Ethernet standard encompasses a number of different physical layer (PHY) standards. We have 10G WAN PHY and 10G LAN PHY.
  • A significant portion of the MMF deployed for 1-Gbps links are legacy types such as Fiber Distributed Data Interface (FDDI)-grade and OM1 fibers, which were not readily suited for a smooth transition to 10 Gbps.The IEEE defined an interface that will cost-effectively allow an upgrade path to 10 Gbps without a change to the existing fiber plant.


The 10GBASE-LRM is a longwave serial interface that includes an electronic dispersion compensation (EDC) chip on the receiving end placed immediately after the receiver optical sub-assembly (ROSA). This enables the adaptive equalization of incoming modal dispersion and thus eliminates the dependency on fiber types. 10GBASE-LRM modules can transmit data over 220 meters on any type of MMF.10GBASE-LRM Standard
10GBASE-LRM is poised to become the solution of choice to upgrade 1-Gbps links to 10 Gbps for reaches of up to 220 meters in campus and building backbones. In the process of producing this standard, the IEEE LRM Task Force took a statistical approach, modeling and testing a number of fibers to define transmitter and receiver parameters that would result in error-free transmission over 99 percent of 220-meter-long fibers deployed in the field.

Long Reach Multimode Transceiver is specified by the IEE 802.3aq form factor connected to a multimode fiber that uses 1310nm lasers as optical sources. Physical coding sublayer is 64b/66b PCS that delivers serialized data at line rate of 10.3125 Gbit/s.

Transceivers provide real time information like Supply Voltage, Laser Bias Current, Laser Average Output Power, Laser Received Input Power and Temperature through the DDM/DOM - Digital Diagnostics Monitoring (DDM) / Digital Optical Monitoring (DOM) interface.










Long reach multi-mode




Serial multi-mode

1310 nm

220 m

Using a 1310nm laser on multimode the distance reach is 220m, there are particular - noon standard implementations over single mode fibers that allow a distance reach of 300m.

The most used end connectors of the transceivers are SFP+ and XFP.

A significant portion of the MMF deployed for 1-Gbps links are legacy types such as Fiber Distributed Data Interface (FDDI)-grade and OM1 fibers, which were not readily suited for a smooth transition to 10 Gbps.The demand is promoted by high-volume applications such as data server connections, wiring closet backhaul, rapid deployment of video services, and the availability of cost-effective technologies such as 10GBASE-LRM. High-speed applications: short-range multi-mode 10 Gigabit Ethernet (10GbE), 10 Gigabit Fibre Channel over Ethernet (10Gb FCoE) or OC-192/STM64 SDH/SONET.

The BlueOptics series of transceivers primarily used with OM1 and OM2 fibers are shown in the following table:

BlueOptics - SKU




BlueOptics© SFP+ 10GBASE-LRM, 1310nm, 220M, Optical Fiber Transceiver, DDM/DOM

- short-range multi-mode 10 Gigabit Ethernet (10GbE), 10 Gigabit Fibre Channel over Ethernet (10Gb FCoE) or OC-192/STM64 SDH/SONET high-speed applications of up to 10.325 gigabits per second.

- Legacy FDDI multimode links


BlueOptics© XFP 10GBASE-LRM, 1310nm, 220M, Optical Fiber Transceiver, DDM/DOM

short-range multi-mode 10 Gigabit Ethernet (10GbE), 10 Gigabit Fibre Channel over Ethernet (10Gb FCoE) or OC-192/STM64 SDH/SONET high-speed applications of up to 11.3 gigabits per second.

- Legacy FDDI multimode links

What is the difference between IPv4 and IPv6?

In today’s era the Internet is used almost everywhere in the world, on almost every device in the world. Today the Internet is used on millions of devices even though 20 years ago in 1990s it was used on around 20. 

Today the key points of any society are online. From the health systems to the educational systems, everyone uses the Internet in one way or another. In some parts of the world people are starting to recognize the Internet as a fundamental right of any citizen.

The Internet works with the help of the Internet Protocol (IP). Each time we are trying to access the Internet with our device, our device is assigned with a unique, numerical IP address. With the help of this IP address, we can send data from one computer to another. Today we are still using the fourth generation of Internet Protocol (IP), the IPv4. This protocol was deployed for the first time back in 1983. Because the world is rapidly going forward and new technologies are rapidly being developed, we are overusing IPv4 addresses and eventually we will need the help of IPv6 to ensure open and constant growth of the Internet.

IPv6 is the sixth generation of Internet Protocol. Its function is similar to the IPv4, but it will eventually substitute the IPv4 protocol. With the rapid and constant exhaustion of IPv4 addresses because of the millions of new devices out there, the leading Network Service Providers and companies started implementing IPv6 solutions in their Networks. However only a fraction of the open Internet has started using IPv6. IPv6 is loaded with many features that can’t be found in IPv4 like expandability, efficient forwarding and interoperability. Its pure size and flexibility offer the next gen innovators to work freely and without limits.

The key new positive things that IPv6 brings, but can’t be found in IPv4, are the quality of services like voice and ecommerce, an ensuring set of QoS features to guarantee performance while forwarding traffic over the Internet and the support for clients to roam between different networks with the help of global notification when you leave one network and enter another.

The main difference is the pure size of IPv6 compared to IPv4. According to mathematicians IPv6 is capable of delivering over three hundred and forty duo decillion IPs. Duo decillion stands for 1039 or the number 1 with 39 zeros after. With approximately 2 billion Internet users worldwide, IPv6 will slowly become irreplaceable. For as long as the Internet exists, IPv4 has been associated with the IP protocol. However today IPv4 is 33 years old. It is a 32 bit IP protocol with 4.3 billion IP addresses, which 20 years ago looked so many. Even though networking experts are constantly trying to minimize the overuse of the IPv4 scope IPs with the help of protocols like the Network Address Translation (NAT) or Classes Inter-Domain Routing (CIDR), the 4.3 billion IPs that IPv4 provides are not enough. To put things in perspective, IPv6 is a 128-bit addressing scheme that provides over 18 trillion IP addresses. These would be enough to provide over 3000 IPs for every living person today. To be more precise, IPv6 could cover each and every micrometer of the Earth’s surface with 5000 unique IP addresses. Because of so many addresses, the use of hexadecimal system to display them is crucial.

The upgrade to IPv6 is inevitable. It is possible for IPv4 and IPv6 to function in parallel but this requires additional protocols and network configurations.

Here are the main differences between IPv4 and IPv6:





32-bit protocol, up to 4.3 billion addresses

128-bit protocol, over 13 trillion addresses

Packet fragmentation

Router and sending hosts

Sending hosts only

Packet header

Includes checksum

Includes options up to 40 bytes

Does not include checksum

Option to use extension headers for optional data

Packet size

Bytes required-576 with optional fragmentation

Bytes required-1280 without fragmentation

Address configuration

Manual or DHCP

Stateless configuration using ICMPv6 or DHCPv6

IP to MAC resolution

Broadcast ARP

Multicast neighbor solicitation





Yes but its optional and external


Even though as of 2014 99% of the Internet traffic is still driven by IPv4, the world started implementing IPv6 in their Operations. The first Internet Exchange that publicly shows IPv6 traffic has been the Amsterdam Exchange. In 2016 the percentage of IPv6 users browsing the Internet via reached around 15%. After the successful test drive of the IPv6 held on June 8 2011, and the successful IPv6 worldwide enabling in June 6 2012, most of the countries in the world started deploying IPv6 in their main public computer and server systems. The Internet Society promoted June 8 2011 as the “World IPv6 Day” and June 6 2012 as the “World IPv6 Launch”.

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LSZH vs. PVC- What cable jacket should I prefer?

In the present era of rapid technology growth and the constant rush for high quality products, we can easily forget about the safety regulations and the various dangers that surround us. This is an extremely important part of the network infrastructure for the IT managers to concentrate on. The large number of networking equipment, together with the cables and possible power weak links, make the Datacenter buildings vulnerable to fire and other possible catastrophes. When designing a network infrastructure, it is important to follow the latest regulations and to follow the various safety tips, no matter the cost, because following them could eventually save a lot of lives.

When it comes to fiber optic cables, the cable jacket is a lot more important part of the network as some may think. The European market is demanding that all cables which would be used in Wide Area Networks (WAN), Local Area Networks (LAN), Storage Area Networks (SAN) etc., meet the latest requirements governed by the IEC 60332-1 which is the standard for Flame Retardant Grade specification. These requirements are met by the Low Emitting Zero Halogen or LSZH cables, and they are not met by the (PVC) polyvinyl chloride cables. Today almost every large installation in Europe must meet this specification. Latest trends show that IT managers even started following the more advanced IEC 60332-3 specification which is a more demanding flammability specification for LSZH cables.

However, the standards in Europe and North America are not the same. While the European standards tend to focus on low-smoke with zero-halogen cables, North American standards mainly focus on a combination of the fire resistance and specific electrical performance, with emphasis on wet electrical qualifications. This is why the North American markets have a tendency of slowly adopting the LSZH products.

The quality of these cables is tested with a variety of tests. They are tested for their electrical performance, flame propagation, halogen content measurement and smoke measurement. The electrical performance test is the most valuable test that separates the insulation material from the jacket material. The most known tests of this kind are the long-term insulation testing in water and the capacitance and relative permittivity tests.

  • The long-term insulation testing in water measures the resistance of the insulating material and its capability to resist the flow of electrons and current. This test is called long-term because it’s conducted over a period of 12 to 36 weeks. The test is done by immersing the insulated conductor in water at the temperature of the specific cable (generally 90 degrees Celsius) while an AC voltage is applied through it. The AC voltage applied must be equal to the voltage rating of the specific cable. The insulation value of the cable is measured on a weekly basis. If the resistance has not decreased by a large value over a period of 12 weeks, then the cable is considered to be safely used in wet and dry applications at the rated temperature.
  • The capacitance and relative permittivity test measures the capacitance and permittivity level of wet-rated conductors. The relative permittivity measures the ratio of the amount of electrical energy stored in the material by an applied voltage and the capacitance is the ability of the material to store charge. The test involves submerging the wire into water and after 24 hours the capacitance and permittivity would be measured. The capacitance is also measured after 7 and after 14 days. The acceptable value for the relative permittivity is 6.0 or less, while for capacitance the requirement is to keep the capacitance value from increasing more than a specified percentage at the given intervals.

The second test is the test of flame propagation. These tests are conducted by stringing together a specified number of eight foot cables samples in a vertical tray and placed in a flame chamber. In the chamber, a flame is applied at the bottom of the cables for 20 minutes. After the flame application, the flame source is removed, and the cables are left to self-extinguish. The test would be acceptable if the measured char at the bottom of the cable is below the prescribed limit of the standard.

The smoke measurement test is conducted at the same time with the flame propagation test. While the cables are burning in the flame chamber a system of complex sensors measure the amount of smoke and peak smoke released. If the total smoke released is less than 150 m2 and the total peak smoke release value is less than 0.40 m2/s the test is passed.

The halogen content measurement is done via an X-ray fluorescence test. The test is passed if the material has less than 0.2% of halogens by weight.

The key difference between PVC and LSZH cables is the amount of dangerous, toxic gases emitted in case of fire. The reduction of the emission of these gases is way bigger with LSZH cables compared to PVC cables. This is mainly because of the compound used in LSZH cables. Even though PVC cables also meet the various requirements of UL 1581, UL 1666 and UL910, they still emit a large amount of toxic and deadly gases. What is interesting about the UL specifications is the fact that those are specifications that specify that the fire can eventually be extinguished faster, but they don’t specify the amount of deadly gases emitted in case of fire.

When comparing these two cables, physically they are very different. You can distinguish one from another just by touching them. PVC cables are softer to a touch because of the material they are made of. On the other hand, due to the rigidness of the flame resistant material needed to manufacture LSZH cable, these cables are rougher and more rigid when compared to PVC cables. Because of the same reason they are also less flexible than PVC cables.  

In case of fire PVC cables would emit a thick, black smoke containing toxic gasses like hydrochloric acids. Low Smoke Zero Halogen cables have a fire resistant jacket which emits no toxic fumes. Because of these safety mechanisms, which could save countless lives, LSZH cables are a bit more expensive than PVC cables. According to the latest Cenelec standards EN50167, 50168 and 50169, the LSZH cables must also be halogen free. The main concern in a fire with PVC cables is the “fire leaping”. This term describes the process of the fire traveling along the cable, leaping from one room to another just by burning along the cables.  

Another key difference is the PVC’s vulnerability to corrosion over time due to various conditions. For example, one of the corrosive substances is oil. Because PVC is a material based on petroleum, they can easily dissolve when coated with oil. This won’t be a problem if oil wasn’t widely used in large factories and industries. PVC cables are also vulnerable to UV exposure. Cables that would be exposed to the sun for long periods of time would need to be replaced more often.

CBO BlueLAN© offers only Low Smoke Zero Halogen cables. All of CBO BlueLAN© cables meet the latest standards including: IEC-61034, IEC-754-1, IEC 60332-1, IEC 60332-3, IEC/EN 60950 and RoHS. Today, even though there are various risks using PVC cables, they are mainly used in horizontal cable runs from the wiring center. Because of the special fire resistant coating, LSZH cables are mainly used for vertical cabling between floors.

What are wavelengths and how can they be used in data transmission?

Wavelength is a physical characteristic of any wave. A wave is an oscillation of a certain amplitude that can travel through a medium. Figure 1 shows a uniform sinusoidal wave. The length marked in blue is the wavelength of this wave. Each wave has its distinct wavelength and frequency.

Figure 1: Sinusoidal Wave

The number of wavelengths propagated in one second is called the frequency of the wave. For example, if one wavelength is travelled in one second, the frequency is said to be 1 hertz. So, the three main characteristics of any wave are:

  1. Speed (v)
  2. Frequency (f)
  3. Wavelength (λ)

The relationship between the above mentioned characteristics of any wave is:

V = f x λ

Fiber optic networks use a light source for data transmission, light travels in the form of wave inside the fiber optic cable’s core. The speed of light is a constant, keeping in view this fact, we can safely deduce that the frequency and wavelength are inversely proportional to each other; i.e., as the frequency increases, the wavelength decreases and as the frequency decreases, the wavelength increases.

Light is an umbrella term used for a wide range of waves, the constituent waves of the visible light can be seen by placing a prism in front of the light source. White light splits in to seven different waves, each of the constituent wave has its own frequency and wavelength. Another interesting fact that can be observed is that the waves having longer wavelengths can travel longer distances as compared to the ones with shorter wavelengths.

Fiber optic communications make full use of the above mentioned characteristics by transmitting and receiving the data signals using light waves. Information is modulated on the wave and transmitted to the other end. More advanced techniques, such as DWDM and CWDM split the light spectrum into various different wavelengths and transmit the data on each of the wave, this data is demodulated on the other end and transferred to the communication equipment.


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