Category: Fiber Transceivers

by http://www.fiber-mart.com

To realize the internal optical network interconnection of data centers, optical transceivers are indispensable. As the number of ports and density increase, half of the cost of optical networks in data centers will be occupied by optical transceivers. At present, 100G interconnection technology has been widely adopted in the newly-built data centers of major Internet companies, and 400G interconnection technology will be commercially available on a large scale in the next 2 to 3 years. Therefore, the implementation technology of 400G optical transceiver has become the focus important part of the industry.

According to this progress, ultra-large-scale data centers are expected to start deploying 400G Ethernet in 2020, and 400G Ethernet will enter the large-scale deployment phase in about 2022.

Early 400G optical transceivers used 16-channel 25Gbps NRZ implementations (such as 400G-SR16), and used CDFP or CFP8 packages. The advantage is that it can borrow the mature 25G NRZ technology on 100G optical transceivers, but the disadvantage is that 16 signals are required for parallel transmission, and the power consumption and volume are relatively large, which is not suitable for data center applications.

In the current 400G optical transceiver, 8 channels of 53Gbps PAM4 (400G-SR8, FR8, LR8) or 4 channels of 106Gbps PAM4 (400G-DR4, FR4, LR4) are mainly used on the optical port side to achieve 400G signal transmission, and used on the electrical port side 8 channels of 53Gbps PAM4 electrical signals, using OSFP or QSFP-DD packaging. Both OSFP and QSFP-DD packages can provide 8 electrical signal interfaces. In comparison, the QSFP-DD package size is smaller (similar to the QSFP28 package of the traditional 100G optical transceiver), which is more suitable for data center applications; the OSFP package size is slightly larger, because it can provide more power consumption, so it is more suitable for telecommunications application.

In terms of optical wavelength, 400G optical transceiver can be divided into multi-mode (MM) and single-mode (SM); in terms of signal modulation methods, they are divided into NRZ and PAM4 modulation (currently PAM4 is the mainstay); distinguished from transmission distance, 400G optical transceivers can be divided into SR, DR, FR, LR; from the packaging form, 400G optical transceivers can be divided into CDFP, CFP8, OSFP, QSFP-DD, etc.

400G CFP8 Optical transceiver

CFP8 is an expansion of CFP4, the number of channels is increased to 8 channels, and the size is correspondingly increased to 40*102*9.5 mm^3. Using 16x25G parallel signals to quickly complete the market and application of 400G products. However, the cost is relatively high, and 16x25G lasers are needed, or a PLC splitter is used to reduce the number of lasers, but the LOSS of the splitter is too high, which directly causes the laser’s emission power to be relatively large, and the cost will also be high. The power consumption is also high, the panel interface density is too low, and the size is large.

400G OSFP Optical Transceiver

The full English name of OSFP is Octal Small Formfactor Pluggable, Octal refers to 8, which means that 56G electrical signals, 8*56GbE are used directly, but 56GbE signals are formed by 25G DML lasers under PAM4 modulation . This standard is a new interface standard and is not compatible with the existing photoelectric interface. OSFP comes with a heat sink, its size is 100.4*22.58*13 mm^3, which is much smaller than CFP8, and its power consumption is relatively low. The maximum is only 15W, but it is slightly larger than QSFP-DD, which requires a larger area PCB board.

400G QSFP-DD optical Transceiver

Q in QSFP-DD refers to “Quad”, which means 4 channels, each QSFP56 is 4*56Gbe, forming a 200G signal; DD refers to “Double Density”, there are two QSFP56 in parallel, 2*200G generation The 400Gbe signal, the full name is Quad Small Form Factor Pluggable-Double Density, this solution is an expansion of QSFP, adding one row to the original 4-channel interface to 8 channels. It is smaller in size than OSFP and compatible with existing 40GbE QSFP and 100GbE QSFP28 interfaces. The original QSFP28 transceiver can still be used. You only need to insert another transceive to achieve a smooth upgrade. Due to the addition of 4 channels, the pins of the upper and lower sides of the electrical interface are increased by one row.

400G COBO Optical Transceiver

COBO is the abbreviation of “consorTIum for on board opTIcs”. The reflector module is directly placed on the PCB board, no longer limited by the front panel interface density. At the same time, the heat dissipation problem can be greatly relieved by reusing the powerful heat sink between the PCB boards. This optical transceiver is small in size. Since t is not hot-swappable, once a optical transceiver fails, the entire board business needs to be stopped and the board need to be taken out, which is very inconvenient.

The optical interconnection network of the data center is facing the transition from 100G to 400G, and technologies for different application scenarios are also competing with each other. As a key hardware device for optical network interconnection in future data centers, 400G optical transceiver also faces challenges in terms of speed, power consumption, volume, and cost.

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In the 5G era, the demand for optical cables is the most prominent problem encountered in the deployment of 5G fronthaul networks. The demand for 5G fronthaul bearer solutions is growing rapidly. In order to reduce the consumption of optical fiber resources, passive wavelength division schemes have been widely used.

Wavelength division multiplexing (WDM), including CWDM (coarse wavelength division multiplexing) and DWDM (dense wavelength division multiplexing), etc. Refers to the coupling of multiple signals of different wavelengths on a single fiber for simultaneous transmission. It has multiplexers and demultiplexers. The multiplexer (MUX) combines multiple signal wavelengths in one optical fiber at the transmitting end; the demultiplexer (DEMUX) transmits multiple wavelengths in one optical fiber at the receiving end. The signals of each wavelength are separated. The main purpose of wavelength division multiplexing is to increase the available bandwidth of optical fibers, which can be expanded through WDM without the need to lay more optical fibers. Therefore, it is widely adopted by telecommunications companies.

What is the difference between CWDM and DWDM?

Tje wavelength intervals of CWDM and DWDM is different

CWDM: Wavelength interval ≥ 20nm, usually 8 bands from 1260~1620nm, 20nm interval;

DWDM: Wavelength interval <10nm, usually 1528~1560nm band, wavelength interval is 200GHz (1.6nm), 100GHz (0.8nm) or 50GHz (0.4nm),

The Modulated lasers of CWDM and DWDM are different

Under normal circumstances, CWDM modulated lasers use uncooled lasers, while DWDM uses refrigerated lasers. Cooled lasers use temperature tuning, and uncooled lasers use electronic tuning.

What are the advantages of CWDM vs DWDM?

Compared with DWDM, the biggest advantage of the CWDM system is its low cost. The cost of the device is mainly reflected in filters and lasers. The wide wavelength interval of 20nm makes CWDM have low requirements on the technical indicators of the laser. The structure of the optical multiplexer/demultiplexer is simplified, so the cost is lower.

DWDM is suitable for long-distance transmission. Compared with CWDM, DWDM with tighter wavelength spacing can carry 8 to 160 wavelengths on an optical fiber, which is more suitable for long-distance transmission. With the help of EDFA (Erbium doped fiber amplifier), DWDM system can work within thousands of kilometers.

What is CCWDM?

After knowing what is CWDM and DWDM, let us understand a mini version of CWDM-CCWDM. What is the difference between it and CWDM?

CCWDM is called a compact coarse wavelength division multiplexer, which is a mini version of CWDM. It is based on the wavelength division multiplexing technology of TFF (thin film filter) and works in the same way as CWDM. The difference is that adjacent channels of CCWDM use parallel beams to cascade in free space instead of optical fibers. Without the optical fiber used for cascading, the size of the CCWDM package box is 10 times smaller than the standard CWDM package.

What is the difference between CWDM and CCWDM?

The CWDM system uses a low-cost, non-cooling distributed feedback (DFB) laser, while the CCWDM’s collimator and filter are welded on a common substrate, and the cascade structure of the two is different.

A three-port filter used for a specific wavelength of CWDM. Its wavelength channel is composed of two lenses and a TFF matched to the specific wavelength. The reflection port of each filter is connected to the common port of the next filter, and the filters are connected by optical fiber connectors, which is a CWDM multiplexer.

The principle of CCWDM is to use the input lens to focus the optical signal with wavelength λ1, λ2…λn on the input fiber to the first filter; the optical signal with wavelength λ1 passes through the first filter and is coupled to the first output lens In the first output fiber, the optical signal with a wavelength of λ1 is separated; the remaining optical signals are reflected by the first glass slide to the next slide for optical signal separation; and so on, until all the signals are separated. The coupling between the wavelength channels is realized in the form of straight rays that follow the “Zigzag” route.

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DWDM (Dense Wavelength Division Multiplexing) is the so-called Dense Wavelength Division Multiplexing technology, which refers to a fiber optic data transmission technology, which uses the wavelength of the laser to transmit according to bits or string line transmission in the optical fiber. And DWDM optical transceiver module is the optical transceiver that combines this technology, there are 40 conventional channels.

DWDM optical transceiver modules have different fields of industrial communication networks, including long-distance backbone networks, metropolitan area networks (MAN), residential access networks and local area networks, etc. Today UnitekFiber will share and learn the relevant knowledge of DWDM optical transceiver modules.

What are the applications of DWDM optical transceiver modules？

DWDM optical transceiver modules amplify DWDM network optical fiber communication and fast Ethernet, gigabit Ethernet, they fix ring topology and reconfigurable QADM etc.

What are the advantages of DWDM optical transceiver modules?

DWDM optical transceiver modules support pluggable and tunable, and there are 40 common channels to choose from. This achievement greatly reduces the demand for independent pluggable modules. On demand, DWDM optical transceiver modules have different channel intervals such as 0.4nm, 0.8nm, and 1.6nm, which can support long-distance transmission up to 100km, which can be used as an effective solution for line bandwidth expansion.

What are the classifications of DWDM optical transceiver modules?

DWDM optical transceiver modules on the market usually include: DWDM SFP, DWDM SFP+, DWDM XFP, DWDM X2, and DWDM XENPAK optical modules.

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As the demand for data centers does not increase, traditional optical fibers not only reduce the space utilization rate of the data center, but also increase the management system of the cabling system. MPO/MTP fiber jumpers greatly improve the space utilization rate of the data center. Therefore, the current MPO fiber optic patch cords and MTP fiber optic patch cords are widely used.

Let’s introduce MTP/MPO fiber optic patch cord.

MTP/MPO fiber optic patch cords are composed of fiber optic connectors and fiber optic cables. According to the number of fiber cores, they can usually be divided into 4 cores, 8 cores, 12 cores, 24 cores, 48 cores, 72 cores and 144 cores. There are two types of MPO/MTP connectors, namely male connector and female connector. The difference between male and female connectors is that the male type has a pair of pins, while the female type does not.

Classification of MTP/MPO fiber jumper:

A. According to the optical fiber transmission mode: single-mode MPO/MTP fiber jumper and multi-mode MTP/MPO fiber jumper.

B. According to the application, MTP/MPO fiber jumpers are divided into branch fiber jumpers and non-branched jumpers. The short-meter fiber jumpers with branches are generally used in the distribution box and chassis, and the non-branched fiber jumpers are generally used. It is the backbone fiber jumper.

Line sequence structure of MPO/MTP fiber optic patch cord: Because the line sequence structure of MPO/MTP fiber optic patch cord connector is complicated, it should be carefully considered when using it, so it is very important to understand the line sequence structure of MPO/MTP fiber optic patch cord connector . The following is the wire sequence of the MPO/MTP fiber jumper: this wire sequence is 12 cores, and the 24 cores have the same structure as the 12 cores.

What are the advantages of MPO/MTP fiber optic patch cords?

The advantages of MPO/MTP fiber patch cords are: 1. Small diameter and small size, allowing the wiring aperture to be increased. 2. The special design of the connector can eliminate docking errors and greatly save installation time. 3. According to the different configuration requirements of users, the corresponding MPO/MTP fiber jumpers can be selected to meet different wiring requirements. 4. Each component has excellent optical and mechanical properties, and the insertion loss is relatively low in a high-speed network environment. 5. The micro-core cable used has a large limit to provide a bending radius, and the size and volume are relatively small.

Application of MPO/MTP optical fiber jumper: 1. High-density optical fiber line 2. Communication and cable television network 3. Data center wiring system 4. Local area network and wide area network user terminal. 5. Data center.

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In the 2G/3G/4G era, mobile communication services are mainly embodied in voice and data services. With the increase in transmission speed and delay brought about by the 5G era, 5G can be deployed in more fields, such as VR/AR, autonomous driving, intelligent manufacturing, smart home, and Internet of Things. In the 5G paving project, the demand for fiber optic cable will also grow rapidly. Among them, the MPO/MTP cable with advantages has begun to gain more attention. This article will take a closer look at the advantages of MPO/MTP cables in 5G data centers.

Seven advantages of applying MPO/MTP cables in the data center:

1. Guarantee the effectiveness and safety of the investment. Although the application of MPO/MTP cable provides high requirements for the integrator’s preliminary and actual site survey capabilities, it can fully protect the investor’s control over the project and the right to use the product, avoiding material waste and project investment risks.

2. Affordable. Overall, the MPO/MTP pre-end approach does not add additional costs.

3. Easy to operate, easy to install, save installation time, and plug and play. We can make a simple comparison, such as laying a 288-core fiber optic cable, 3 construction workers, 2 sets of equipment, using traditional fusion fiber method, laying about 2 hours, and the time required for the fusion fiber plus installation is about 8 hours, a total of about 10 hours. And If the MPO/MTP pre-fabricated cable is used, the laying time is still 2 hours, but the installation time is greatly reduced, which takes about 45 minutes, which undoubtedly has a huge advantage in time cost.

4. The MPO/MTP pre-cast cable is fully tested in the factory, and no additional products are added during the installation process. The field test operation is simple.

5. The fiber link protection is sufficient, no solder joints and bare fibers are exposed to the air, and there are no problems such as aging and joint breakage.

6. Safe and easy to maintain, the mechanical performance of the MPO/MTP pre-harvest cable splitter is excellent, and the maintenance or operation process will not affect the normal use of the fiber.

7. Reinstallable and removable, the MPO/MTP patch panel can be quickly plugged and unloaded and reinstalled as needed.

Compared with ordinary fiber optic cable, the main features of MPO/MTP cable are high density and pre-formed end, and finally embodied in MPO/MTP multi-core connector.

Throughout the development of the industry, fiber optic connectors have two distinct stages of development. The first phase is to save space, fiber optic connectors evolved from the traditional FC, ST, SC to LC, MTRJ. The second phase is not only to save space but also to meet the requirements of multi-core use, fiber optic connectors evolved from LC, MTRJ to MU, MPO/MTP.

With the rapid development of 5G, data center interconnection, fiber sensing, and next-generation fiber technology, ultra-large capacity, ultra-high-speed, ultra-long-haul optical transmission networks will become necessary for 5G data center construction. Therefore, the technical and cost advantages of MPO/MTP cable make it very likely to become the mainstream way for future operators to build 5G data centers.       

by http://www.fiber-mart.com

Fiber cable is a kind of communication line in which a certain number of fibers are assembled according to a certain way. Some of them are wrapped with sheaths or outer sheaths, which are used to protect the fibers and realize the transmission of optical signals. Optical cables usually consist of one or more fibers.

There are different types of fiber cables, and there are various classification methods. Here are some commonly used classification methods.

First, classification according to structure

According to the structure, it can be divided into layered stranded fiber cable and bundle tube fiber cable.

(1) Layered stranded fiber cable

The layered stranded fiber cable is a rounded core composed of several reinforcing parts which hold the loosen sleeve around the center of the fiber. Metal or non-metal reinforcements are located in the center of the optical cable, and loose sleeves containing fiber cables are arranged around the reinforcements.

(2) Bundle tube fiber cable

The loose sleeve of the central bundle tube is located in the center of the optical cable, and the metal or non-metal reinforcements are arranged around the loose sleeve. The bundle-and-tube type optical cable inserts the optical fiber into the spiral space loose sleeve made of high modulus plastic. The sleeve is filled with waterproof compound. A layer of water-resisting material and armor material are applied outside the sleeve. Two parallel wires are placed on both sides and polyethylene sheathed cable is extruded.

The central bundle tube type fiber cable has simple structure, simple manufacturing process, better protection for optical fiber than other structures, which can withstand side pressure, thus improving the stability of network transmission; small cross section, light weight, especially suitable for overhead laying; flexible number of optical fibers in bundle tube.

Second, according to the use environment

Fiber cables can be divided into indoor and outdoor cables according to different use environments.

(1) Indoor fiber cables have smaller tensile strength and thinner protective layer, but they are relatively lighter and more economical. Indoor optical cables are mainly used in horizontal wiring subsystems and backbone subsystems.

(2) Outdoor optical cables have high tensile strength, thick protective layer, which are usually wrapped in metal skin. Outdoor optical cables are mostly used in building group subsystems, and can be used in outdoor buried, pipeline and other occasions.