Knowledge About GPON SFP Transceivers

by Fiber-MART.COM

GPON stands for Gigabit Passive Optical Network. GPON is one of the key technologies that are being used in fiber-based (FTTx) access networks, including fiber to the home (FTTH), fiber to the business (FTTB), fiber to the curb (FTTC), etc. GPON system contains two main active transmission components, namely optical line termination (OLT) and optical network termination (ONT) or optical network unit (ONU). Modern OLT and ONT/ONU use compact fiber optic modules to achieve the triple-play GPON services. These modules are known as GPON SFP transceivers. This post will give a comprehensive introduction to GPON SFP modules.

 

What Is GPON SFP?

GPON SFP is one type of gigabit optical transceivers that are used in GPON system, which is compliant with ITU-T G.984.2 standard. It is a bidirectional module that has SC receptacle and works over simplex single-mode fiber optic cable. A GPON SFP module transmits and receives signals of different wavelengths between the OLT at the Central Office side and the ONT at the end users side. GPON SFPs utilize both the upstream data and downstream data by means of Optical Wavelength Division Multiplexing (WDM).

 

GPON SFP: Class B+ vs. Class C+

GPON SFP transceivers are categorized into GPON OLT SFP and GPON ONT SFP or GPON ONU SFP depending on the devices they are used in. And there are Class B+ GPON SFP and Class C+ GPON SFP. The major differences between them are the transmit power and the receive sensitivity. The table below lists the Tx power and Rx sensitivity of Class B+ GPON SFP and Class C+ GPON SFP.

 

By using Class B+ or Class C+ GPON OLT SFP, it can support up to 32 or 64 ONTs at customer premises respectively. And a C+ OLT SFP can be used with B+ ONT SFP as long as the loss budget of the link is appropriate.

 

How’s the GPON SFP Different From Conventional BiDi SFP?

Although GPON SFP belongs to the gigabit BiDi SFP family, it differs from “normal” BiDi SFPs in some aspects. Here’s a comparison between GPON SFP transceiver and conventional BiDi SFP transceiver.

 

Signal Transmission Mode

In terms of conventional gigabit BiDi SFP transceivers that are mainly used in backbone network, the optical transmission mode is point to point (P2P), i.e., they must be used in matched pair. A BiDi usually has LC receptacle instead of SC receptacle. Here’s an illustration of P2P transmission mode.

 

The transmission mode of GPON SFP is point to multi-point (P2MP). One GPON OLT SFP at the Central Office communicates with multiple GPON ONT SFPs with the help of fiber optic splitters. This is why we usually see a GPON infrastructure is in a tree shape or a tee shape.

 

Transmission Distance

The transmission distance of conventional gigabit BiDi SFP can be up to 160 km over single-mode fiber cable when using 1590nm/1510nm and 1510nm/1590nm wavelengths. GPON OLT and ONT/ ONU SFP transceivers support a transmission distance up to 20 km with 1490nm/1310nm and 1310nm/1490nm wavelengths.

 

Benefits of Using GPON SFP

Using GPON SFP is considered a more convenient and cost-effective solution for the end customers. And it also reduces the devices that need to be provided by the Internet service provider (ISP). Before the GPON ONT SFP was released and used in GPON networks, the ISP usually needs to install at least an optical modem (a type of ONT with a fiber optic port) and an IP access router, and a Set-Top-Box or video recorder might also be needed if IPTV services are required. The separation of different devices inevitably increased the cost for GPON services.

 

The newly used GPON SFP is in smaller size and integrates the triple-play services. It has lower consumption as well. The ISP provides a GPON ONT SFP to the customer. This module is usually installed in the hub/router handed to the customer by the ISP. The customer is also able to unplug the fiber optic patch cable and the GPON ONT SFP from the ISP’s hub/router, and then plug them in his own router/switch that is white-listed by the ISP.

 

Conclusion

GPON SFP transceivers are typically used in the two main active transmission components OLT and ONT/ONU in GPON optical networks. They are essential in keeping the high-bandwidth communication between the service provider and the end users over a distance up to 20 km. GPON SFPs are classified into Class B+ and Class C+ and the main differences are their Tx power and Rx sensitivity. This module has simplified the implementation of GPON services. It benefits both the service providers and the end users to some degree.

8 smart steps for buying life insurance

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Life insurance can form a vital part of your family’s financial stability and well-being but, if you’re like most people, you may find the thought of shopping for the right type of coverage a little daunting. Fortunately, these eight simple steps can guide you along the way.

1. Determine whether you actually need life insurance

Most people do, but not everyone. If no one depends on you financially, if you have no debt and would leave an estate with enough cash to pay its own taxes and expenses, you probably don’t need life insurance. If you do not meet these criteria, you probably will need individual life insurance.

2. Calculate how much life insurance you need

There are two important questions to ask:
What financial resources will be available to survivors after your death? For simplicity, consider three categories of resources: (1) Social security and other retirement-related survivor benefits; (2) group life insurance; and (3) other assets and resources. It is also important to know when these resources will become available—for example, social security survivor benefits are payable immediately to a surviving spouse with dependent children, but only after age 60 if there are no children.
What financial needs will your survivors have after your death. For simplicity, consider three categories of requirements: (1) final expenses; (2) debts; and (3) income needs.
Then subtract your survivors’ financial resources (step #2) from their financial needs (step #3) to determine how large a policy to buy. Many people are underinsured, often because they skip these steps or take a shortcut (such as simply buying a multiple of annual income). For more help in determining the right amount of life insurance, see: How Much Life Insurance Do I Need?
3. Consider other objectives you may have for your life insurance

Some types of life insurance policies include a savings feature that can be used for purposes other than paying death benefits.

4. Determine what type of life insurance best meets your needs

Essentially, there are three types of life insurance policies—term life, whole life and universal life. If you need the insurance for only a specific period of time, or are on a limited budget, a term policy, which has lower premiums, may be a good fit. If, however, you need the insurance for as long as you live and want to accumulate savings, a whole or universal policy may be a better choice.

5. Find out if you need to add any “riders” to the policy

There are two that you should consider—waiver of premium and guaranteed insurability. Some policies come with one or both included with the basic contract but, if not, it is generally a good idea to add them. Waiver of premium pays the life insurance policy premium for you if you are disabled. Guaranteed insurability permits you to add to the death benefit without providing additional evidence that you are in acceptable health.

6. Shop around

There are many ways to save money when buying life insurance, but they don’t always entail paying a lower premium immediately. That said, life insurance is a very competitive business so quotes can vary significantly between companies.

7. Decide whether to pay premiums annually

In most cases, it is better to pay annually rather than in installments because there is often a relatively large additional charge for paying smaller amounts more frequently.

8. Tell your beneficiaries about your life insurance policy

Once the policy is issued, inform your beneficiaries the company that issued it, where to find the paper copy of the policy and any specifics about what you want them to do with the death benefit. While is rare for people to be unaware they are the beneficiary of a life insurance policy, it does happen and you want to make sure that the benefit will not go unclaimed. And store your documents so that they can be easily accessed by your beneficiaries.